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Oz Report

topic: bridle (32 articles)

Krys' Drogue Incident 8-15-21

Thu, Oct 7 2021, 10:43:50 pm MDT

New and untested chute

bridle|drogue|Greg Dinauer|Krzysztof "Krys/Kris" Grzyb|Larry Bunner|Moyes RX|triangle

Larry Bunner reports:

On 8-15-21 Krys Grzyb and Greg Dinauer set an 83km triangle task from Twin Oaks airport in Whitewater, WI east to East Troy, northwest to McDermott airport and then southwest back to Twin Oaks. Greg aborted the task early and flew back to the airport. Krys was doing well getting over 5200’agl on nine climbs. He tagged the first two turn-points and was headed back to the airport.

To this point he had been in the air for 2hr 15min of which over 1½ hours was above 4200’. The winds were 5-9mph from the southeast. Sustained climbs over 1000’ were averaging about 350fpm with one climb averaging 770fpm. He found a thermal just past the last turnpoint 18km out and climbed 300+feet to ~4400’. He needed about a 12:1 glide to get back with a crossing tail wind. He confidently left the last climb knowing he could make it and even if he hit increased sink, he would hit a thermal soon enough.

He went on a long glide sinking over 300fpm and was soon down below 1000’. He selected a narrow field of grass along a farm for his LZ. Approaching from the southeast at 500’ he unzipped the drogue pouch and began extracting it from the pocket. His intent was to deploy it near the ground but the drogue slipped away and accidentally deployed.

Immediately the glider turned right and his sink rate increased to 600+fpm. He pulled in on the control bar, the glider began to pitch down and the sink rate increased to over 900fpm (peak). Thinking the drogue malfunctioned, he reached back to grab the bridle but couldn’t find it. He instantly began to correct for the turning dive. With extreme effort the glider rounded out pointing downwind and just above the corn. The glider, slowed somewhat by the corn, whacked in hard but the glider and Kris were miraculously unharmed. Pretty shaken, he called to the airport to get a retrieve; Greg and Chico showed up quickly to help get the equipment out of the corn.

Krys has used a drogue chute for many years. This particular drogue was developed to train runners to improve their speed. It has one long bridle that runs back to the chute shroud lines. These lines are short relative to the length of the bridle. He used this type of chute for several years with the drogue deploying aft of the keel. This spring he purchased a new drogue from a different manufacturer and replaced his old worn one. He did not compare bridle lengths before installation. Up to this flight the new drogue had not been tested/deployed. After landing, Kris discovered that the keel had penetrated between the shroud lines and the drogue was affixed/centered around the keel.

The bridle length was a couple inches shorter than his previous drogue. When the drogue accidentally deployed, the position of the drogue effectively provided a lifting surface on the end of the keel. When the control bar was pulled in to increase sink rate, the forces on the aft end of the keel decreased the nose angle further thus progressively increasing the sink rate (to the point the nose was pointed at the ground). It took close to all of Krys’ strength to push the bar out far enough to overcome the resistance to level out the glider before entering the tall corn.

In the moment, he focused entirely on recovering the glider turn and descent and felt there wasn’t enough time or altitude to throw his main parachute. His Moyes RX 3.5 sprogs were at the factory settings. Corrective actions that Krys has taken or intends to take include: shorten bridle to prevent keel interaction, add an extra line to one of the shrouds and the harness loop to give access to the pilot to deflate the drogue, and adding a drogue release so the drogue can be cut loose from the pilot.

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Bridles, releases, 2m antennas

Thu, Apr 3 2008, 4:30:03 pm PDT

Bridles

Purchase a few pieces of useful gear from the Oz Report

bridle|release|antenna

https://OzReport.com/bridlescables.php

Or https://OzReport.com click Store, Goodies.

I've decided to keep a small inventory of a few useful, but lightweight, items that can be easily and quickly shipped to pilots who need a slick aerotow bridle/release or a simple to install and powerful antenna. The items can be purchased on-line and I'll get them right in the mail to you.

For example:

Bridle, Spectra or Vectran for Pro tow, $15.

Click on above to view a higher resolution image. The top one is the Spectra, the bottom, the Vectran.

Go here: https://OzReport.com/bridlescables.php.

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Fatality Report

Learning from an aerotowing accident from last year

Mike Haas

Tue, Aug 30 2005, 2:00:00 pm GMT

accident|aerotow|Angelo Mantas|bridle|cart|Dave Whedon|Dragonfly|equipment|fatality|foot launch|HG & PG Magazine|Matt Taber|Mike Haas|Moyes Litesport|Moyes Xtralite|safety|tail|tow|tug|ultralite|winch

Angelo Mantas «Angelomant» writes:

Analysis - Mike Haas Fatality

Scenario - Mike’s accident happened during midday thermal conditions. He was flying a Moyes 147 Litesport, aerotowing it off of a launch dolly. Several witnesses saw the accident, but I give Dave Whedon’s account the most weight, because a) He saw the entire event, from start to finish, and b) He was watching several tows intently to see what conditions were like, since he hadn’t towed in a while.

The tug was given the “go” signal. Dave said that almost as soon as Mike launched off the cart, he appeared to be having difficulty with both pitch and roll control. Then, at around 50' - 60’, the glider pitched up radically and started arcing to the left. Somewhere around this time the weak link broke, or the pilot released. The glider continued rotating left and dove into the ground, first hitting the left wing tip, then nose. The glider’s pitch was near vertical on impact, confirmed by the fact that the control bar, except for a bend in one downtube, was basically intact, whereas the keel and one leading edge snapped just behind the nose plate junction. This all happened fairly quickly. Based on witness and tug pilot accounts, the glider was never over 100’.

Despite help reaching him almost instantly, attempts to revive him proved futile. Mike suffered a broken spinal cord and was probably killed instantly.

Causes - In examining the circumstances surrounding the accident, it seems to me that several factors, which by themselves might not cause major problems, combined to lead to Mike's losing control of the glider.

1) New, high performance glider.

2) Larger size glider than what he was used to.

3) A fast flying tug (Kolb)

4) Flying through a thermal just after launching.

5) A rearward keel attachment point on the “V” bridle.

Mike had only one previous flight on his new Litesport, in laminar coastal ridge soaring conditions. Although he flew over two hours, he probably never flew the glider at the speeds encountered when aerotowing. Mike had many aerotows on a Moyes Xtralite, but according to Matt Taber, the Litesport doesn’t track as well at high speed. The Litesport was also bigger than his Xtralite, which would make it less responsive and harder to control.

The tug used was a Kolb ultralight. Although this tug had an increased wing span than normal Kolbs, it still tows at a higher speed than a Dragonfly. I can tell you from my own experience that it is harder to tow behind a faster tug.

Soon after launching, the glider and tug flew through a strong thermal. This is confirmed by witnesses watching the tug, and the tug pilot’s reporting a strong spike in climb rate.

Here is where some controversy might come in: on examining the wreckage, Arlan (tug pilot) saw where the upper “V” bridle was attached, and immediately felt that that was a possible cause of the accident. It was attached at the hang point, and in his opinion, was too far back for a stable tow. Since then, there has been debate on whether or not that was a safe attachment point. That positioning on the keel was recommended to him by the seller, and apparently many other pilots have towed a Litesport from the same position. Shortly after the accident, some pilots in Wisconsin did an aerotow of a Litesport from slightly behind the hang point, and reported it towed fine.

I agree with Arlan that the upper bridle attachment point contributed to the accident. The test done in Wisconsin was done early in the morning in stable conditions, and the pilot weighed 50 more pounds than Mike. Just because others have managed to tow with this upper bridle position, doesn’t mean it’s safe, especially for pilots on the light end of the weight range.

To sum up, Mike was flying a glider that was bigger than what he was used to, with less stability at the higher speeds needed to stay behind the Kolb. Even with Mike’s hang gliding experience, these factors would tax his abilities. These difficulties would be magnified by the de-stabilizing effect of the rearward keel bridle attachment and the faster speed of the Kolb tug. Already struggling (as witnesses state), when Mike hit the thermal, a difficult situation became impossible. Mike lost control, and either locked out or stalled, leading to his dive into the ground.

How can we prevent this from happening in the future?

A proper keel attachment would have made the glider fly faster without a lot of bar pressure. It also would have made the glider more stable in yaw, because the tow force would be farther in front of the CG. My own experience has been that since moving my keel attachment further forward, tows are much more stable.

Using a tail fin - Tail fins definitely help stabilize gliders on aerotow, especially high performance gliders that may be less stable in yaw. A too rearward keel bridle attachment can be overcome with a fin. Many aerotow parks use tail fins on their demo gliders. The downside to fins is that they can make thermaling difficult on many gliders, but they can still be a valuable tool to make your glider safer while you figure out where your keel bridle attachment should be.

First tows of new gliders in smooth conditions. It is much easier to aerotow a new glider when the air is smooth. Learn how the glider tows in calm air, make any equipment adjustments necessary, then later tow in midday, thermal air.

Practice flying your glider fast before aerotowing it. If you foot launch or static tow your glider, you can literally fly for years without ever flying at the speeds involved with aerotowing. Even platform/payout winch towing doesn't involve those speeds. Practice pulling in the bar and keep it there. Easy? Now try to make a small heading correction and keep it. Good chance you’ll be PIOing all over. This kind of practice definitely pays off.

Wind streamers along runway. It’s agreed that Mike hit a strong thermal shortly after launching. Placing streamers on both sides of the runway, at regular intervals, would help detect if a thermal is coming through the takeoff area. If all the streamers are pointing the same way, it’s safe to launch. If some of the streamers start moving other directions or reversing, it’s obvious some kind of turbulence is coming through. This is not a new idea, it’s not expensive (wood stakes and surveyor's tape) yet I’ve never seen anyone do this. Maybe it’s time we start.

Mike was a Hang IV pilot with over twenty years experience. He was not a “hot dog” and was very safety conscious. No one who knew Mike could believe that this happened to him. Although I feel I have a better understanding now of what happened, I can’t help feeling that if this could happen to him, none of us are safe.

(editor's noticed: There was an earlier, and different accident report published in June in HG/PG Magazine.)

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Bridles

Tue, Feb 15 2005, 2:00:01 pm EST

News from Europe.

Bart Doets|Bridle|Mike Nooy|Pascal Legrand|Rohan Holtkamp|Rohan Taylor

Bart Doets «bart.doets» writes:

The HS release:

First, the HS release (see above) which is very common in Holland. When I dug out this picture, I noticed that the "saddle" where the pin rests is actually much deeper then on my own release, which is not even a recent one. I never noticed it before, but it seems there are different versions of this release, probably because the current manufacturer had it DHV tested for the German market. In this old version, one can imagine release problems if the towline is angled downward. On the newer one, that would not be a problem. The HS release is double to enable winch towing.

Of this type of release Rohan Holtkamp writes:

Mike Nooy's release was triggered but at the angle of the rope that was greater than 90 degrees to the 'finger' at its max open point, so the rope did not come off the end. The release 'finger' was mounted firmly to the front of the harness, as with all the H.S systems. We call them Euro tow systems.

The release 'finger' pivoted only horizontally and less than 180 degrees. The finger should be able to pivot vertically as well as horizontally and in excess of 180 degrees to release in any direction. It needs a UNI joint, like found on a car tail shaft but smaller and covered so it will not snag.

Bart writes:

What we call a HS release here has pins that rotate in two planes; the pin can open away from its saddle (vertically), and can also pivot horizontally (horizontally, if you lay the release flat on the table that is). It has been proven to open with the line pulling every direction imaginable.

pascal legrand «Legrand.pascal» writes:

This works. I think it is made by Koch. Bought in France, more expensive than the loop but worth every euro. Mechanical, no slack, Just bang on it and it goes. 2 releases . I use one for aerotowing. The metal ring is a must, as it was said.

Bart continues:

This release I made myself a year ago, based on what is known in the USA as a barrel type release, but this way it works straight as a chest release. I had some troubles with it when I started using it; I wore through several weaklinks until I attached the weaklink to a ring and hooked the ring into the release. Apparently the parachute type pin had too sharp edges or maybe a little burr.

That's why I am currently making a new one following the same principle, this time with a pin I made from a nail that I bent myself; I soldered the eye closed because this is where the weaklink is pulling and it should be absolutely smooth:

Not been tried yet, but as you see it is simple enough.

Some folks have mentioned a string to a finger as an extra quick release option. With this release, a string could be attached to the barrel if wanted. Personally, I think that the time spent until you decide to take action, is more decisive then the time needed to open most any release.

Discuss bridles at the Oz Report forum

Bridle killed the hang glider pilot

Fri, Feb 11 2005, 1:00:02 pm GMT

Spinnaker shackles

Robin Strid

bridle|Dave Broyles|fatality|HPAC|release|Robin Strid|Rohan Holtkamp|safety|tow|USHGA|weaklink|Worlds 2005

"Special Pro Tow" https://OzReport.com/8.190#5

Other releases: http://www.hanglide.com/miva/merchant.mv?Screen=CTGY&Store_Code=LME&Category_Code=AE and http://www.birrendesign.com/LKAero.html

Scare «Gerry» writes:

There are several different types of bridles described, diagrammed, or pictured here: http://hpac.ca/tow/HPAC_Tow_Manual.asp#3.3. We would like to have more pictures too, and would also appreciate any comments or advice you might have. How is it done where you are?

Robin Strid died because the weaklink wrapped around one leg of his spinnaker shackle. The weaklink was too strong to break. The weaklink was made of multiple loops. At least, that's the story that I heard Rohan Holtkamp, who investigated the accident, present to the team leaders at the Worlds.

The ends of the legs of the shackle were thicker than the middle. The weaklink caught up on the thicker ends of the legs after the shackle was opened by the release cable. Look at the first article linked to above to see the fat legs.

One of the legs rotates when the release is opened and the weaklink has to slide over the thicker leg. I'm communicating with Rohan to get better answers to what happened to Robin and how to avoid this in the future.

Another release system: http://www.flycyprus.com/release.html

Dave Broyles (USHGA Safety and Training Committee Chairman) comments on the spinnaker shackle here.

I'll have much more on releases soon. Send me your thoughts on bridles and releases and any pictures of bridles.

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Bridle pictures

Thu, Feb 10 2005, 11:00:04 am EST

Send in your pictures of your bridle types.

bridles

bridle|Gary Wirdnam|photo

Gary Wirdnam «gwirdnam» writes:

Lots of talk about different types of tow release, which are good etc., but no pictures. I don't know what a "Pro-tow" release looks like. More to the point, many readers won't have a clue what type of release Robin was using and may still be using one themselves. A 'rogues gallery' would help.

So please send Davis digital photos of various bridle types to help me and other's out.

Discuss "Bridle pictures" at the Oz Report forum   link»  

Bo's bridle

Tue, May 18 2004, 6:00:00 pm GMT

Deformed carabineer.

Bo

accident|aerobatics|Aeros Ltd|Bob Lane|Bo Hagewood|bridle|G.W. Meadows|injury|insurance|John Claytor

John Claytor «johnclaytor» writes:

I hope Bo pulls through this okay. This is a shot of the bridle attachment and as you will note the rectangular carabineer is deformed with the nut backed off. This is how it was found by others.

Seeing him spiral in, will stay with those who saw it for some time to come. He is a very lucky man indeed.

There doesn't seem to be a need for the second carabineer and that leads Bob Lane here at Quest to speculate that Bo neglected to hook up the main carabineer to the loop at the bottom of the hang strap. This loop is located between the back plate and the outer shell of the harness. It would seem that Bo might have pushed his bridle up between the back plate and the shell and then not got around to finishing the installation. The carabineer would have been slightly bent as it was pulled out of the harness.

G. W. Meadows «justfly» writes:

As many of you know by now, our friend, little buddy and pal Bo Hagewood has had a serious hang gliding mishap. As I write this, his life is not in danger, but he is in ICU in Norfolk Virginia. Current reports to me say that he has multiple punctures in a lung, a lacerated liver and kidney as well as as some damaged vertebrae.

It seems that the worse (most concerning) injury however is his wrist/forearm. I am currently traveling on business, but my wife Jan is working the phone back home to keep me updated. According to her latest update, Bo's wrist is broken in ten places and there is concern about his future use of the arm or even his keeping the arm.

Again, keep in mind that this is early info and may change (this situation has changed in reports to me three times in the last twelve hours - never getting better).

Please pray or think good thoughts for Bo.

There is rumor that he has insurance. If this rumor turns out to be false, then I'm sure that the hang gliding community will continue to do for Bo what it always has.

Regarding his accident, my partner and Aeros Test Pilot - Sunny Venesky is now arriving to the area and will do a full analysis of the wreckage. If any part of the glider failed (which it appears it did) we will determine whether that part was damaged previously and then proceed from there. No stone will go unturned on this investigation. The smart thing at this point would be for all persons flying Combat L's to not perform aerobatics until more is known. Please understand that I'm not saying there's a problem - don't misread this - but there seems to be no doubt that the glider failed for some reason. This is the glider that Oleg flew in both Florida meets.

We will update via Oz Report and our website - www.justfly.com - as soon as we know anything.

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Static towing

Mon, Jan 5 2004, 7:00:01 pm GMT

static towing and retractable bridles

bridle|competition|crossbar|harness|Hay|job|Len Paton|release|safety|towing|weaklink

Len Paton <lenpaton@westserv.net.au> writes:

It's great that you've refreshed your thoughts on static towing. I've always found it so relaxing compared to aerotowing. Less intense, less effort, less anxiety. I have always felt I have more control and feel much more secure close to the ground.

You might understand why most car towers at comps feel a bit perplexed when days are cancelled because of gusty conditions. I was astounded last year (or was it the year before?) when somebody in the safety committee at an Australian competition (who was aerotowing) commented to me a few days after a day was canned, that "we were more concerned about the pilots static towering than ourselves". I'm not sure it was a cop-out, but … an interesting comment.

Apart from knowing your thoughts about canning marginal days, (from our attempt to have a pilot vote last year at Hay) I think people on the safety committee should have some experience in the towing systems present at the comp. They will also be less influenced by pilots with a "hidden agenda" who are using an alternate towing system. At least the discussion at Hay last year may have brought to the fore many pilot's concerns. For a couple of years it looked like overly cautious safety committees were going to spoil some good competitions.

Retractable bridle systems: Some pilots have developed good systems that "hitch" or lock themselves in the extended position until the bridle is given a shake (or usually the response after release). I have seen pilots significantly distracted trying to pull their bridles out to full extension as the driver takes the slack out of the rope.

Also these pilots are reluctant to reduce the starting tension from the nominal 15kgs before launch in light and variable conditions, leading to some dodgy launches.

One fellow pilot has thought out a positive locking system to prevent the bridle retracting until the VG has been pulled for the first time. A loop attached to the end of the retract bungee is passed thru a small hole (or slot) in the side of the central crossbar fitting. This is pinned on the other side of the cross bar fitting by a pin attached to the nose by a light piece of chord, without any slack. As the VG is pulled, the loop is pulled off the pin, pulls back thru the cross bar fitting and allows the bungee to do its job.

I use an adapted Moyes type system: one-to-one, with the 4 metre bridle feeding thru a ring out in front. After I release I have only this bridle hanging from my waist which is easily stowed before the start gate. My release involves a link knife in the top position, just in front of my hang point. A weak link passes thru a link knife and is attached to the keel via a "quick link" (oblong metal loop with screw gate).

The link knife is attached to my VG rope using a small D shackle. An extra foot off VG rope is pulled back thru to allow the link knife to sit over the weak link without tension. Pull the VG a couple of inches which retracts the link knife and cuts the weak link. Of course this is not my main fail-safe weak link.

I have a 120kg weak link out in front between the bridle and towrope. In fact I have 5 ways to get off: 2 voluntary and 3 involuntary. The link knife release up top; a "curved pin in a tube" on my waist (very light and small); the main weak link out front; a 60-70% weak link that the link knife cuts and another 60- 70% weaklink incorporated with the belly release. They need to be greater than ½ the front weaklink because the bridle is not doubled back on itself.

With these options I thought the extra redundancy of a Jack knife was unnecessary and haven't transferred it across from my old CG1000 harness.

Discuss "Static towing" at the Oz Report forum   link»

Bare Wires

Fri, Oct 24 2003, 8:00:02 am GMT

accident|bridle|George Lutkowski|Glen Volk|Kathleen Rigg|Mike Barber|Moyes|parachute|Peter Birren|Rodger Hoyt|wires

Peter Birren «peterb» writes:

In 1991 (12 years ago), George Lutkowski did just what was described (Some day there will be a chute deployment by a pilot in a glider that has stripped wires and the parachute bridle will be cut in half) and his chute bridle was severed, leaving material embedded in 54 inches of bare flying wire. George will never fly again and has lost 90% of the use of one hand due to nerve damage, all in the name of better(?) performance.

Who wants to be next? From severed noses to bridles to bystander injuries, stripped wires are a hazard to everyone.

Rodger Hoyt «rodger» writes:

The potential cutting of a parachute bridle is avoidable.

When removing a worn parachute bridle several years ago, I discovered to my shock, how easily Type 18 bridles are severed with minimal heat and friction! The thought of this type of material sliding along a flying wire, stripped or not, under the tension of deployment, made me afraid to ever use it again. That's when I switched to Kevlar. Even a well worn Kevlar bridle was impervious to my hot knife, and required a concerted effort to cut at all. Kevlar has the additional advantage of being much thinner and therefore bundles smaller in your 'chute container.

Unquestionably, most aspects of parachute design and construction are compromises, each having its pros and cons; Kevlar is no exception. Kevlar fell into disfavor some years back when leading parachute manufacturer Rich Pfeiffer denounced it for lacking the elasticity necessary to absorb the shock of a terminal velocity deployment without destroying the parachute itself. But Rich's perspective was that of a former skydiver; few hang glider deployments are at terminal velocity.

Another drawback of Kevlar is, if the occasion ever arises where a hook knife is needed, it would be useless on Kevlar - plan on cutting your harness mains instead. It's also rumored that Kevlar is less tolerant of UV; I keep my bridle sheathed.

Each pilot must decide what characteristics are most important to him. I'm confident with Kevlar.

Also, if cut bridles are a concern, one should consider the airframe material. 6061 responds to impact by bending; 7075 (the current material of choice) shatters, leaving sharp edges (don't ask how I know this!).

Kathleen Rigg «Kathleen.Rigg» writes:

I'd just like to point out that I do not believe my accident was actually caused by the wires (which I did not strip but are delivered by Moyes with no plastic coating). In fact after inspecting the glider and assessing the angles and evidence of blood on the glider my injury appears much more likely to be from violently forcing my nose up between the swages at the very nose of the glider rather than from the actual wires.

There is also some doubt as to whether the wires caused Mike Barber's accident as well - in fact it is more likely to have been caused by the back edge of the carbon base bar (which is very similar to an accident Seppi had shortly before Mike).

I'm not saying that stripped wires are necessarily a good thing, but I don’t believe either of the two accidents that Glen Volk mentions can be accredited to stripped wires!

Discuss stripped wires at OzReport.com/forum/phpBB2

Discuss "Bare Wires" at the Oz Report forum   link»  

The Spanish ATOS “incident”

Mon, Jul 7 2003, 6:00:05 pm GMT

accident|aerotow|airline|airspace|altitude|Angelo Crapanzano|bridle|Carlos Avila|certification|cloud|control frame|DHV|environment|equipment|Felix Ruehle|Florida|foot launch|general aviation|GPS|harness|injury|job|landing|military|Moyes Xtralite|parachute|Ron Richardson|safety|site|spin|Swift|tail|technique|tow|towing|tumble|USHGA|Wallaby Ranch|winch

David Cross <d.cross@chello.nl> writes:

I have recently had the unfortunate experience of departing controlled flight in an ATOS rigid wing hang glider. I have written this report to share the experience with my fellow aviators so that any lessons learnt may be shared and the accident assessed by those with a better insight in this field than I.

Description of Flight Conditions

I had launched in the mid afternoon with an aero tow from Aerotow.com's facilities near the town of Avila in central Spain. I was planning to fly some cross country under the tuition of the highly experienced Ron Richardson. It was my second flight of the day. On the previous flight I had found the conditions to be weak with the thermals broken and the climbs poor and I had not been able to stay up for long. The afternoon however improved with the cloud base lifting to about 7000' altitude (average ground elevation of 3000'), with promising cumulus development downwind to the east and no sign of the previous day's overdevelopment.

The second aero tow was bumpy but easy to handle on the ATOS with its excellent control harmony between pitch and roll. I was waved off in some lift over a small ridgeline to the south east of the field. I again found the lift to be broken and the climb weak. Ron was at this stage further to the east overhead the town and was calling a 300'/min climb on the averager. As I was at this stage too low to get over to him I focused on what I had in order to build more altitude. I scratched up to 4800' altitude and then ran for a good looking cumulus on the way to Ron's position.

Loss of Control

Entering the Thermal

I rolled right hand into the lift under the cumulus and worked hard to centre it. The conditions were choppy but not rough and smoothed out somewhat above 5000' altitude to a steady 300 fpm up. The conditions downwind were now looking really good and through each turn I was scanning to pick up Ron's Avian Cheetah on the horizon, and I could hear Darren Blackman heading in towards us on his Swift. Things were at last coming together after a week of poor conditions. I was relaxed, thoroughly enjoying the ATOS and looking forward to the afternoons flying.

Turn Reversal

I had in the last turn noticed a slight increase in lift in the southern sector of my circle. I glanced down to see if there were any birds marking the core and was presented with a magnificent stork circling left hand counter flow to me with slightly intersecting circles. After one more turn I saw that (as always) he was doing a better job than I and so I planned a turn reversal into his circle.

The reversal worked out well. As the stork slid under my nose I experienced a moderate pitch up from the stronger lift and eased the bar in to lower the nose and accelerate while rolling out of the right hand turn into a left hand circle. Due to the fair conditions I had been thermalling at 40-45 km/h (25-28 mph) indicated airspeed (IAS) with 20-25° of bank and had felt very comfortable at this speed.

(editor’s note: Unless the thermal is absolutely light (50-100 fpm) and full with no turbulence, I’m flying at 34-38 mph. The speeds indicated above are much too slow for the conditions described.)

As I had now accelerated into the stronger lift I estimate that the IAS was approximately 48-50 km/h (30 mph) as I started the reversal. The flap was set at 8-10°. The reversal was initiated with moderate spoiler application - I estimate ⅓ to ½ deflection. The altitude was now 6000' (about 2500' AGL due to the ridge below).

Departing Controlled Flight

As the left hand turn was established I felt a light short period aerodynamic buffet on the control frame and almost simultaneously experienced a very rapid nose down pitch rotation through approximately 90° of pitch. I estimate the pitch rotation rate to be 50 -60°/sec. There was also some left hand roll rotation, although this was less than the amount of pitch rotation. I was not aware of any significant yaw.

As the departure started my assessment was that the glider was auto-rotating and that I was in the incipient stage of a spin. I had been thermalling with the bar in the upper chest to lower chin position. As the nose down pitch started I rapidly moved the bar in to the mid chest position in an attempt to reduce the angle of attack, un-stall the wing and stop the autorotation. This appeared to stop the left roll rotation rate but had little effect on the rate of nose down pitch. During the latter part of the initial nose down rotation I estimate that the g loading on my body was 0 - 0.5 g (I felt almost weightless).

The glider then appeared to stabilize very briefly in the vertical nose down position before rotating extremely rapidly in pitch to the inverted position. This second rotation was violent and uncontrollable. As it happened I felt a powerful rearward pull from my hang strap and the control bar was pulled from my grip. I was thrown hard into the undersurface of the glider which was now inverted, next to the A frame. I estimate that this pitch down rate was well in excess of 90°/sec.

The glider now stabilized in the inverted position while descending in what appeared to be a relatively gentle oscillatory spiral. I was somewhat disorientated at this point and so may not be too accurate about the motion of the glider. I do however recall some spiral motion and some oscillation above and below the horizon.

I was lying on the undersurface of the wing to the left of and outside the A frame. I immediately checked the leading edges and tips and observed no apparent structural damage. I assessed that I had sufficient altitude and attempted to right the glider and reached for the A frame to do this. When I grasped the left down tube to attempt to right the glider, the glider entered a very disorientating oscillatory rotation but remained inverted. I assume this was caused by spoiler deflection when I moved the A frame.

After two rapid rotations it did not appear to be recovering. At this stage I was losing situational awareness with respect to the height remaining for recovery. In addition the gliders unstable motion had me concerned about the possibility of being knocked unconscious.

Parachute Deployment

I thus looked for clear air and deployed my emergency parachute hard in the direction of rotation half way between the right hand wingtip and the keel. The parachute deployed immediately and then appeared to semi collapse as the glider was rotated by the parachute deployment into the upright position, swinging me hard to hang to the outside of the A frame. The parachute then reopened immediately.

The system of parachute, glider and pilot now became extremely unstable with the parachute and the glider appearing to work in opposition. The glider appeared to accelerate and pitch nose up, causing the chute to collapse and then re-open before the cycle was repeated by the glider. From my vantage point the parachute was describing a sine curve-like path across the horizon while collapsing partially and re-opening in sequence with the pitch motion of the glider.

The glider and parachute appeared to be rotating rapidly about each other with the centre of this rotation somewhere between the glider and the parachute. At no stage was the parachute positioned above the glider. The centripetal acceleration of this system rapidly became very high. I estimate the g loading to be approximately 3 g and I was swung out helplessly under the wing clear of the A frame unable to control the system at all.

Stabilizing the System

I now broadcast a Mayday call, and informed Ron that I had deployed the parachute and was going down. I described my status and informed him that it did not look promising. At this stage the rate of descent and particularly the angular rotation appeared to me to be very high and I was sure that ground impact in this configuration would have severe consequences.

After several high g rotations I managed to grab the hang strap behind my neck and pull myself toward the A frame and grasp a down tube. Adrenaline is a wonderful thing. I then pulled myself into the A frame. This had an immediate positive effect. The parachute stabilized above the glider, the angular velocity reduced and the g loading reduced. I was now descending through about 500' AGL with a moderate oscillation but no angular rotation at all. I now called Ron to inform him that the situation was under control and proceeded to describe my probable touchdown position to him.

Touchdown

I descended onto the slope of a rocky tree covered ridge. Before impact I positioned myself as high into the A frame as possible as I was not sure what the rate of descent was and I wished to protect myself from any impact on what appeared to be very rocky terrain. I kept my legs bent to absorb as much shock as possible.

I was fortunate to impact into the crown of a moderately sized tree. The A frame took much of the initial impact of the branches. The glider was then swung out of the top of the tree throwing me out of the A frame. As I fell to the ground the glider hooked onto a branch and my fall was arrested with my feet 12cm off the ground. I was completely uninjured. I transmitted to Ron that I was down and safe and that he should cancel any ambulance.

The only apparent damage to the glider was a broken main spar and associated sail damage approximately ⅓ in from the right wingtip. This occurred on ground impact and not in flight. My assessment was that the glider was completely undamaged until ground contact.

Discussion

As with any aviation accident there are several lessons to be learnt. Most accidents are not caused by a single event but by a combination of factors. Often an accident could have been prevented if just one of these factors, however minor it may have seemed at the time, could have been identified and stopped. I will now discuss my background, what I think may have been the contributing factors to this accident and the lessons learnt from it. This is obviously my subjective opinion and I welcome any discussion on these points that may offer a more informed insight.

Flying Experience and Background

I am a USHGA intermediate rated pilot who has been flying for three years. I did my initial training in the French Alps mountain launching and completed my training at Wallaby Ranch where I also obtained an aero tow rating. I did a further foot launching course at Lookout Mountain where I obtained cliff launch, flat slope launch and assisted windy cliff launch ratings. My flying has taken place mostly in Florida and the Alps and has always been under the supervision of more experienced pilots. I currently fly a Moyes Xtralite. One month prior to the accident I had flown under the supervision of Chris Dawes in the UK where I did some winch foot launch training and some aero towing as an early season refresher. Prior to this I had last flown the previous late summer in the Alps.

I am a current airline pilot flying Boeing 747's and a current Air Force reserve pilot on fighter type aircraft. I hold a Glider Pilot's License although I am not at present current on sailplanes. I have some experience flying paragliders although I have not yet completed my license. My total flying experience is 8000 hours.

I have mentioned the military experience as I feel it is relevant with respect to my experience in spinning three axis control aircraft. My air force background has provided me with extensive spin training. I have been fortunate to have had the opportunity of spinning a variety of aircraft, from military trainers and fighters to general aviation aircraft, aerobatic aircraft and sailplanes.

Two weeks prior to this accident I carried out a maintenance test flight on a military trainer that included several multi turn full spins and recoveries. I thus feel that I may be considered current as far as spin identification, entry and recovery on three axis aircraft is concerned. This has relevance as there has been much discussion about the advantages of doing spin training on three axis aircraft before flying rigid wing hang gliders.

ATOS Experience

I had come to Spain specifically for the opportunity of flying the ATOS. At the time of the accident I had flown 11 flights on the ATOS for a total of 5.00 flying hours. All flight had been under the supervision of Felix Ruehle and I had been extensively and professionally briefed by him on all aspects of the glider.

Although this was my first experience on a rigid wing hang glider I had felt comfortable and confident on the ATOS from the first flight. I had on the second flight in smooth evening conditions flown the glider to the stall and found the recovery to be simple. I had confidence thermalling the glider in the moderate conditions I had experienced and at no stage had any reservations about the handling of the glider. I found the control harmony particularly pleasant and aero towing simple.

(editor’s note: An inexperienced hang glider pilot, new to an ATOS, was flying it too slow in a thermal.)

Equipment

The glider was a standard ATOS. I had for most of the week prior to the accident been flying another standard ATOS. The hang point for the accident glider (as on the previous glider) had been adjusted towards the forward centre of gravity (C of G) limit, appropriate to my hook in weight. On the accident glider my hang position was slightly higher than that of the glider I had flown previously in the week and the trim speed was slightly lower. Both the hang position and the trim speed were well within safe limits. The glider was fitted with an A.I.R. horizontal stabilizer.

I was using a Woody Valley Tenax harness with the parachute mounted on the right chest. The harness was fitted with a Metamorfosi Conar 18 Gore parachute, which was just over one year old and had recently been repacked by myself. No swivel was fitted to the bridle. My weight is 72 kg making a hook in weight of 87kg.

Airspeed information was provided by a Brauniger Galileo set to indicated airspeed (IAS) mode and a mechanical pitot system fitted by Felix. I used the mechanical system for airspeed reference as I had not yet calibrated the Galileo and was not sure of the reliability of the airspeed display.

Departure from Controlled Flight

I feel that the departure from controlled flight had two distinct phases, a non divergent autorotation phase, and a divergent pitch instability phase.

Autorotation Phase

The autorotation phase I would describe as a gust induced stall in the turn followed by an autorotation and an incipient spin (the incipient stage of the spin being where the aerodynamic and gyroscopic effects of the spin are still influenced by the initial flight path of the glider - in this case a left hand turn). Although the nose down rotation of this phase was rapid it did not feel to me to be divergent. I thus do not feel that the gust had at this stage placed the wing at an AOA/hang point loading combination that had exceeded any static stability margins.

I was surprised by the limited aerodynamic stall warning and the rate of the initial nose down rotation. For these reasons I think the gust onset was significant and rapid. All my previous spinning experience in aircraft had led me to expect an initial rotation rate in roll and yaw that equaled or exceeded any initial nose down pitch rotation. As the initial nose down rotation started I had reduced the AOA aggressively. This seemed to stop any further roll or yaw rotation but had little effect on the rate of nose down pitch rotation. At no stage did the glider enter a stabilized spin.

I feel that there are several factors that could have contributed to the initial autorotation.

Firstly the glider was trimmed slightly slower than that to which I had been used to on the previous ATOS I had flown. As stated this was well within safe limits but may have caused a tendency towards slightly slower flight if I was distracted.

Secondly, I was using flap to thermal. This would move the bar position slightly back and I would, if focused primarily on bar position, have the tendency to move the bar further forward than required.

Thirdly, I had completed a turn reversal prior to the autorotation and the spoiler deflection would have caused some nose up pitching moment. If not corrected this would cause an obvious reduction in IAS and place the glider closer to the stall.

All the above factors are conducive to slower flight. However I am accustomed to flying aircraft that require accurate speed control and feel that I was very aware of the IAS while thermalling. I was also aware that the spin behavior of rigid wing gliders can be unpredictable and had no desire to explore that environment. My thermalling speed of 42-45 km/h (26 mph) felt comfortable for the conditions I was experiencing. I have since been informed that it was perhaps on the low side but not unsafe.

(editor’s note: Pilot is unaware that he is flying too slow.)

I had thermalled at similar speeds in equivalent conditions for most of the week without ever approaching any stall margins. The accuracy of the airspeed reference must also be considered. As mentioned previously my primary reference was the mechanical pitot system as I felt it was more accurate than my as yet un-calibrated electronic reference.

Some points with respect to the turn reversal technique. I normally unload the wing (thus reducing the AOA) before initiating any reversal in order to improve the roll rate. This obviously also results in an increase in IAS. Whether my technique was sufficient to counter any pitch up due to spoiler deflection may be debated. I did not notice any significant pitch up during this particular reversal. My limited experience on the ATOS could of course preclude this.

In addition I had experienced acceleration on entering the increased lift prior to the reversal. I had countered the nose up pitch that this had caused and so feel that my IAS margins on entry to the turn reversal were probably sufficient for normal conditions. I had as well been briefed on the "rule of thumb" safe range for forward and rearward bar positions and at all times flew within this range.

I thus think there must have been some significant gust effect present. Simply approaching the stall in a turn should not result in the almost immediate and rapid rotation experienced with minimal stall warning. I have described the conditions as moderate. I was experiencing an average climb of 300 fpm with maximum instantaneous readings of 1000 fpm.

However, Ron Richardson reported some strong turbulence while descending through the airspace I had been flying in, shortly after I deployed the parachute. My assessment is that a gust rapidly exceeded the critical AOA of the wing. As I was not yet fully established in a stable turn, there would have been some asymmetric loading on the wing, possibly resulting in the auto-rotation. I feel that this is supported by the fact that my rapid reduction in the AOA had no appreciable effect on the pitch rotation rate.

Pitch Instability Phase

I will now discuss what I consider to be the second phase of the departure. During the initial auto-rotation I had not experienced any reduction in g loading on my body - the hang point still felt loaded. Although the initial nose down rotation was high, I still felt that I had some control input and that the glider would recover. However, as the glider passed through about 60° nose down I experienced a reduction in g loading and felt almost weightless.

From this point I felt I no longer had control of the glider and I was unable to hold the bar in any longer. This is when the rapid rotation to the inverted position occurred and I lost my grip on the control bar. Perhaps the excessive AOA of the wing combined with the unloading of the hang point caused the static stability margins of the wing to be exceeded, causing a divergent rotation in pitch. The first auto-rotation phase initially felt controllable. The second phase of pitch instability was definitely not controllable.

Lessons Learnt

Thermalling at higher speed, steeper bank angles and higher g loadings, while not necessarily providing an increase in stall margin, will improve the damping in pitch and make a departure less likely.

It would be of value to calculate the exact stall speeds for the actual wing loading at various appropriate bank angles. With an accurate IAS reference sufficient margins could be applied to these calculated stall speeds for safer thermalling. An accurate IAS reference is obviously necessary. Of even more value would be a vane type AOA reference (Here's hoping!).

I found the ATOS easy and a pleasure to fly. However, in retrospect I feel that more time spent exploring the performance of the glider in smooth air would have been of benefit. I think in particular, the effect of flap on trim speeds and bar position, spoiler effect on pitch in turn reversals and approaches to the stall in wings level and turning flight should have been more fully explored before flying in more challenging conditions.

I think that my initial reaction to the auto-rotation phase was correct. Moving the bar in reduces the AOA and places the centre of gravity in the best possible position for dive recovery. Should this happen again I will do the same while attempting to hold on tighter. I do however feel that it was impossible to maintain grip on the control bar during the rotation to the inverted position.

Some comments on pilot experience. I was very excited to be offered the opportunity to fly the ATOS by Felix, as I consider myself a low time hang glider pilot. His briefing was comprehensive and gave me confidence in the glider while making me aware of how it differed from other gliders I had flown. I flew the glider conservatively and felt very confident with the general handling.

The afternoon following the accident I flew another standard ATOS in moderate thermic conditions for a 1 ½ hour flight. While understandably nervous at first the pleasant handling of the glider allowed me to settle down and soon regain my confidence. In summary I experienced nothing in the handling of the ATOS that should exceed the abilities of an intermediate pilot. In most respects I found the ATOS easier to fly than an intermediate flex wing hang glider.

Some discussion on three axis spin training for rigid wing pilots. I feel the main benefit of this would be spin entry recognition and reduced disorientation. The spin entry techniques and recovery procedures for a three axis aircraft are different to that of a rigid wing hang glider and themselves can vary dependant on the design of the aircraft. Practicing these procedures would I feel have limited benefit for rigid wing pilots and may even reinforce incorrect techniques. In this accident the main benefit to me of my spin training was recognition of the initial situation and orientation in the unusual attitudes experienced.

Some points on the parachute deployment. It has been suggested, considering the glider was undamaged while inverted, that I could have tried harder to right the glider before deploying the parachute. In retrospect I am glad I did not. I lost a lot of height trying to stabilize the spinning parachute/glider combination. Had I deployed the parachute any later I might have impacted before stabilizing the system. At the time I did not feel that this would have been survivable.

I have discussed this with Angelo Crapanzano from Metamorfosi. He commented that although I was experiencing high g loadings, because the centre of gravity of the pilot/glider/parachute system would have been very close to the pilot/glider combination, my rotational speed would actually have been quite low. In addition he said that my descent rate would perhaps have been even less than when I had stabilized the system. He thus feels that even when the system was not stabilized, it was survivable. The perception from the pilot's point of view remains unpleasant.

In addition it is not certain how the glider may have reacted in the attempt to right it and there is a strong possibility of pilot injury in attempting this. This may then preclude parachute deployment. I thus feel strongly that if one is fortunate to survive a loss of control situation uninjured, the priority is to get the parachute deployed immediately. Considering the instability after parachute deployment, I feel the priority should be to get ones mass as close as possible to the hang point.

Angelo Crapanzano recommends that one gets as close as possible to the nose of the glider, or at least in front of the hang point. This can however be difficult and the A frame is a familiar refuge when under stress and can provide impact protection. It would have helped if I had held onto some part of the A frame before deploying the parachute, as this might have prevented me from being flung away from the A frame as the parachute deployed and righted the glider.

Had I been able to remain closer to the A frame the spiral motion might not have developed. I also feel that some thought should be given to the option of releasing from the glider prior to parachute deployment. All my complications were due to the fact that I was still attached to the glider.

I am very pleased that I had the Conar HG18 parachute. The rate of descent once stabilized was acceptable and the opening time impressively fast. It worked as advertised.

Some discussion on communications and search and rescue procedures. I was able to transmit a Mayday to Ron Richardson seconds after deploying the parachute as I had a transmit button fixed to my thumb. Ron demonstrated professionalism and true airmanship. He acknowledged my call, was overhead my position within minutes, plotted GPS co-ordinates and arranged a rescue. He then landed in a difficult location and was at the accident site within 30 minutes.

Had I been seriously injured Ron's actions would have been potentially life saving. The lessons here are to always fly with someone, be able to communicate effectively with them, even under duress, and always be prepared to assist effectively in an emergency. I had water in my harness but no first aid kit or emergency rations. This has been rectified.

Conclusion

In summary, I suggest that this accident was a result of a gust exceeding the critical angle of attack of the wing by a large margin. This resulted in auto-rotation with a rapid nose down pitch and unloading of the hang point. The static stability margin of the wing was exceeded and the wing experienced a divergent rotation to the inverted position.

Contributory factors were the relatively low indicated airspeed while thermalling, the effect of flap on the control bar position, pilot technique in the turn reversal and the pitch up effect of spoiler deflection.

Flex Ruehle’s Comments

I have attached an email from Felix Ruehle with his comments on the report and the incident.

You report is excellent however I think it's hard to see how quickly or slowly everything happened because my experience is that reports from stress situations follow a different clock.

Since hang gliding was born turbulence can be a problem for safe flying. However different developments improved the safety. One of the latest developments is the fixed V-tail with a lifting airfoil from A-I-R. How does it work? The glider is designed to have the same pitch up moment with tail like the standard ATOS with 0° flap.

With thermal, take off and landing flap setting the pitch up moment is significantly higher with the V-tail. Additionally the V-tail increases pitch damping very significantly with all flap settings. Of course instead of a tail the sweep angle can be increased too to get the same pitch damping effect. However this didn't work out as well for the ATOS, because higher sweep in combination with wing bending would cause dynamic problems.

With the V-tail the glider flies significantly more comfortable. In opposite to the opinion of some pilots, that a positive pitch up moment only protects a glider from tumbling, this is not the case. It is a result of several flight incidents with all types of hang gliders and as well with the hang glider drop test made by the DHV a few years ago that even with a certified hang glider it is possible to tumble.

According to my opinion the main parameters are: Pitch damping which can be increased by higher speed and by the wing area distribution in flight direction. For example a higher sweep angle or a tail, increase pitch damping as well as a forward pilot position. Pitch up moment. This is the moment which must be above a certain value for certification. Small distance from aerodynamic centre to CG.

For example a short A-frame is positive. High airspeed in relation to the turbulence is positive too.

The incident

The air was not very smooth this day and there was over development with rain shortly after the incident at this spot. Ron who landed close to help Dave (thanks Ron) hit some strong turbulence too. However, the day wasn't that rough that pilots usually would stop flying.

According to my opinion the tumbling from Dave was caused due to low airspeed in relation to the turbulence. The thermal speed under this condition was already little slow. The reversal turn reduced the speed probably further. This for example is a very good practice in smooth condition, doing reversal with constant speed. Take care: If you don't pull in during the reversal the speed drops.

I flew to the same spot the next day and felt comfortable with about 55km/h (34 mph) as min. thermal speed. This day looked smoother to me as the previous day.

Does the tail improve the safety? At the online contest (olc) 2002 the ATOS is the glider which has flown the most km before any other wing (including flex wing) and the ATOS flew much more km than other rigids, too. Many pilots have flown sometimes under extremely hard conditions and have reported the good behavior under turbulent condition.

It looks to me like active flying is getting more and more important. With the fast gliders the pilots have the possibility to fly with extra speed or high bank angle without losing too much of performance and it looks too me like the ATOS with the new V-tail is a step to improve pilots safety to a very high level even with the incident of Dave.

Under strong condition the glider gets extra stability with high bank angle and higher speed. While doing a reversal you can easily lose speed and the pilot has no extra g loading. I think this can be an interesting discussion how different pilots handle turbulent air.

Discuss "The Spanish ATOS “incident”" at the Oz Report forum   link»

Paraswivels

Fri, Jun 20 2003, 6:03:06 pm GMT

Angelo Crapanzano|bridle|DHV|Europe|harness|Juan Lara|parachute|power|video

Gary Douris <gary77douris@yahoo.com> writes:

We have tested the swivels both from an aircraft and from relatively slow hang gliders. Angelo is correct in assuming that the swivel can cause the bridle to drop below the bag when the glider is traveling more or less straight down.

Our rationale is that very few cases have the glider traveling in a straight vertical down attitude. On all but one of the several broken gliders I have seen they have had some horizontal track. In this case the bag with canopy has a relative wind to help move it away from the glider and deploy.

Remember, parachutes do not work every time. There are too many variables with gliders in different configurations to guarantee a successful deployment in all cases. We can only do our best.

As far as your canopies or anyone else’s, if the canopy does not clear the end of the wing and the bridle catches on something a swivel can make all the difference.

One of ours was caught on the wing tip a few years ago and wound up with 97 twists in the lines and bridle. The canopy was completely collapsed because the glider was spinning so violently. The pilot survived since he landed in some bushes and we soon after started using swivels.

No canopy design is sure of not having a problem with the bridle snagged. If the glider spins badly enough the canopy with collapse no matter the design. The reason we put the swivel where it is is to get it as far from the glider as possible so if the bridle does snag the swivel still has a chance to work. It also adds weight to the bag which helps extend the bridle faster.

If I can find it I will send you a video of a test we did a few years ago with a spinning canopy. It opened my eyes and made a believer out of me.

The L.A.R.A. comes with the swivel optional.

Angelo Crapanzano <angelo@metamorfosi.com> writes:

I agree with you again: it's just a matter of compromise and different experiences.

I've seen most broken gliders falling straight down and out of 276 real openings that I know with my parachutes only one may have needed the swivel (the parachute didn't fully collapse and the pilot was uninjured). I'll be very interested in looking at the video: there is always something to learn.

Our experience brought us to different solutions of the same problem and I'm actually sorry to have involuntary started this debate on swivel: the number of saves proof both systems are safe enough.

Angelo continues:

As I wrote in a mail last year on OzReport (https://OzReport.com/toc.php?Ozv6n27.shtml) personally I don't like swivels (mainly because I feel they are not necessary for my parachutes) but I agree they could be useful in other parachute design. In that article I already explained, in a fast way, why I don't like the swivel near the junction bridle-parachute, but I was not exhaustive. Actually I thought nobody was using the swivel in that position until, a few weeks ago, I've seen a parachute like that (as you know, in Europe the swivel is not common and, in Italy, almost unknown).

Sorry but, to be clear, I've got to start from the way tests are normally done. I you want to understand what I mean, please have a look to the videos which are better than a thousand words.

When making tests with forced opening from an airplane or skydiving it is the parachute strength, stability and sink-rate that is tested but not the deployment sequence in a real hang gliding emergency situation:

- If the deployment is forced with a static line the deployment bag design makes almost no difference because it's the dummy weight which pulls the parachute put of the pod.

- If the parachute is tested while skydiving, everything happens at very high speed: very little in common with a "normal" emergency situation.

The DHV, to test the opening time and sequence, lets fall at the same time from zero speed, a dummy and the parachute still closed in his deployment bag: the parachute have to fully open within 60 meters. In this test the torso dummy is obviously falling faster than the pod thus it is the force due to the different velocities which extracts the parachute from the pod. (Kok7 video) (There is quite a lot to say about this test too but, again, it's another long story…)

For your knowledge, the terminal speed of the dummy is probably close to 100 m/s (360 km/h or 225 mph) while the terminal speed of a parachute still closed in his pod is around 12 m/s (43 km/h or 27 mph). As a comparison the terminal speed of a parachutist (quite variable because depends on his position) is normally considered as 50 m/s (180 km/h or 112 mph). To make it clear for everybody, the terminal speed is the maximum speed achieved by a body falling in the air. It is the speed at which the drag force equals the weight force thus the body would not accelerate and keeps constant speed. Of course, depends on the weight and the shape of the body. Things would be much easier to calculate without air because everything would fall at the same speed, but we could not fly either :-)

Lets go back to reality and imagine the pilot lets the parachute fall (something which happens very often) instead of throwing it forcefully. Just a quick note: to throw the pod forcefully and in the right direction helps a lot the deployment sequence but, try hanging in your harness close to the ground, it's almost impossible to fully stretch bridle, line and canopy horizontally just with your force. Moreover you would never be able to throw it upward more than a couple of meters: in my opinion the parachute needs to be able to open on his own, even if it's not thrown forcefully.

As everybody knows, in many real emergency situations, if the glider is not much broken the pilot is falling relatively slowly and, quite often, slower than the parachute still closed in his deployment bag. In this situation it is the deployment bag which falls down compared to the broken glider. Again it's the difference in speed between broken glider and closed deployment bag which extracts the parachute (but this time the other way round compared to the DHV test). In this situation, once the canopy is out of the deployment bag, the parachute is pointing down then it "flies" up (still not inflated) and can open only once above the pilot, with the lines stretched. (Kok4 video)

If the glider is badly broken the pilot will fall down very fast. The situation gets similar to the DHV test: the deployment bag goes up compared to the glider and the parachute comes out of the pod because of the different velocities: once the parachute gets out of the pod it is already above the pilot, with the lines stretched, and opens. (Kok6 video)

But what will happen if broken glider and pod are falling, more or less, at the same speed? In this case there is very little difference in velocity to open the pod. What actually opens the pod is the drag on bridle and lines which makes an arc between pilot and pod and extracts the parachute. It is evident that in this case there is very little force available to open the pod. (Remember that this force this force goes up with falling speed power of two). (Kok5 video)

Just for your knowledge, my experience says that the slower the glider is falling, the longer the falling distance needed for the parachute to open.

But what does this matter with swivels? It does matter, in my opinion, but I want to point out that what follows is just theoretical and is not backed by any tests on the influence of swivel position on parachute deployment. I’ve never made any test on swivels because, as I already told, I think in my parachutes the advantages of a swivel are out weighed by the disadvantages.

A swivel adds more or less 200 grams (0.5 lb) to the bridle (weight of the short webbing included) which is a good percentage of the whole suspension system (bridle + lines); moreover it's concentrated in a single point. Let's see what will happen in the three cases if the swivel is, more or less, at the junction between lines and bridle:

If the deployment bag falls down compared to the pilot, the weight of the swivel helps the bag falling down but then the canopy (stretched but still closed) has to lift the swivel weight to get above the pilot. This, for sure, will slow down the opening and will slightly increase the time the canopy is level with the broken glider, thus increasing the chances of tangling. Moreover the swivel weight, concentrated at the junction bridle-line, tends to shape bridle and lines making a V, thus bringing the canopy closer to the wreckage.

If the deployment bag goes up compared to the pilot, the weight of the swivel will slightly slow it down (compared to the pilot) until the bridle is stretched then would make no difference. It would be practically impossible to measure any difference in opening time, especially if the tests are done at high speed. These, as far as I understood, are the tests made by Rob and that's why he didn't find any problem adding the swivel at the junction bridle-line.

If the deployment bag falls down at the same speed of the broken glider the weight of the swivel would counterbalance (at least partially) the drag on bridle and lines. Moreover the swivel weight, concentrated at the junction bridle-line would shape them like an m thus bringing the canopy closer to the wreckage.

Now you know why I feel it would be better to have the swivel at 1 or 1,5 m (3-5 ft) from the pilot where it would not make any problem.

I would like to point out again that what I wrote is absolutely theoretical. I never wrote (nor intended to mean) that a parachute with the swivel at the junction bridle-lines will not work or is dangerous. There have been lots of saves with this configuration to prove the system is, for sure, safe enough. I only meant to say that, in my opinion, in some particular cases, the opening time could "slightly" increase and the chances of tangling could "slightly" increase too. Slightly is quoted simply because it's practically impossible to value it. On the other side the swivel at the junction between bridle and line is in the perfect position to avoid any twisting of the canopy. Like always any solution has advantages and disadvantages and it's up to the manufacturer to find "his" best compromise.

Hope this mail would be considered as an attempt to improve parachute design and not the start of a useless polemic (I didn't even know the Lara had the swivel in that position). It is not my intention to denigrate anybody else’s design. To make it in easy words: logically I would prefer my Conar, but I would have no problem flying with a Lara, even with the swivel in the "wrong" :-) position.

Discuss "Paraswivels" at the Oz Report forum   link»

Chutes – handle on the wrong end of the sack

Fri, Jun 20 2003, 2:03:05 pm EDT

Betty Pfeiffer|bridle|gear|parachute|Sandy Dittmar

Red <red@xmission.com> writes:

I agree with Betty, about sequenced deployments for reserve parachutes being a great idea.

I agree with Angelo, about the real advantages of a "diaper" deployment system, and that a sequenced "diaper" system is the -best- of all possible choices. I will shortly be buying exactly that.

I had one like that for most of my HG flying so far, but my gear was stolen, a couple of years ago. So, I bought a sack-deployed reserve; it was a "deal", and delivery was rapid. Hey, I'm not rich, and I was needing airtime… :-)

My new 'chute arrived with the deployment handle installed at the wrong end of the sack! I was shocked. My retailer called the company, and only after some discussion, the defective sack was replaced. Every reserve in that same shipment came, like mine, with the handle at the wrong end, also.

If the handle is installed at the open end of the sack, that is correct. You should be able to toss this parachute cleanly. If the handle is at the closed end of the sack, however, that can be hazardous! A hard toss may break the elastic bands securing the sack (even if they are new ones). The empty bag might go flying, but the pilot can have lines, bridle and a scattered canopy billowing around them.

From my own experience: At an indoor parachute clinic, in Sandy, Utah, several pilots with "wrong-handled" sacks experienced this "empty bag toss" parachute malfunction, in one evening. For one of these malfunctions, the pilot's canopy draped itself over the pilot's head and shoulders. Every pilot fell silent at the sight of this prone form, enshrouded in white. Not one person in the hall laughed. The pilot himself was frozen in thought.

Would everybody with a sack deployment system, just go check that they have a sack with the handle at the correct end? Thanks; every pilot is somewhat "family", to me. While we are throwing "experience" times around, I was flying, and building HG for a living in 1975. I worked at one of the only two HG shops in Denver for a bit, building airframes and harnesses. I was a certified instructor for over a decade in SLC, Utah; h4 with all endorsements. Coupla thousand hours, now, and counting.

Not relevant, but free advice, and maybe worth the price, for new and low-time HG pilots, at my website: http://www.xmission.com/~red/

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Parachutes - Angelo responds to Betty »

Mon, Jun 16 2003, 6:03:03 pm GMT

accident|altitude|Angelo Crapanzano|Betty Pfeiffer|bridle|harness|job|nylon|parachute|Rob Kells

Angelo Crapanzano <angelo@metamorfosi.com> writes:

It's difficult to answer Betty Pfeiffer because she has a preconceived negative attitude and her letter looks more like a personal attack than anything else, quite a different behaviour from Gary Douris and Rob Kells. I'm going to answer in detail hoping this would not bring to a never ending debate.

"… revealed the importance of controlled deployment sequence"

I agree, but it could be achieved (or not) both with an envelope or a diaper.

"…a properly designed deployment bag … can allow the pilot a second (or third) throw if he/she did not clear the wreckage"

How can one make a second (or third) throw? The only way is to pull back the bag using the bridle, but a "properly designed deployment bag" (regardless if envelope or diaper) would not allow it because it will open before you get it back!

"Systems that allow parachute components to "dump" into the air to various degrees, such as diaper systems, risk tangling with the wreckage, out of sequence deployments which can cause temporary partial inversions, canopy inversions, line over situations and other problems."

I totally agree, but the proper deployment sequence could be achieved (or not) both with an envelope or a diaper. Anyway, why a properly designed diaper should "dump" into the air more than a properly designed envelope? Betty perfectly knows old style envelope bags (those with the opening on the opposite side of the handle) gave lots of problems, "dumping" the parachute in the air (or even into the harness!). It's the same with old style, flour flap diaper bag (but I never manufactured one of those).

My "five flap" diaper (which has been copied by many parachute manufacturers all over the world) has a perfectly staged and obliged opening sequence: bridle - lines - canopy. Of course one could prefer envelope or diaper (like Gary Douris and me) but this is quite different from saying a system is bad just because has a different name, if it does the same job.

Once the parachute is in clear air with a suspended weight, it will want to organize itself. In the process friction can cause heat, which can cause damage. This will not happen with the proper opening sequence: bridle-line-canopy, which could be achieved (or not) both with a diaper or an envelope.

"Last month a HG pilot threw his emergency reserve packed in a "diaper". It took him 1500 feet of altitude loss untangling lines so the parachute could open…"

I'm sure that's true as I'm sure Betty knows similar stories with emergency parachutes packed in an "envelope". If she doesn't I could tell her some.

"The use of line sleeves is analogous to a slider used on parachutes. It slows parachute inflation by restricting the line spread."

That's not correct: the sleeve is short enough not to make any difference in opening time. It does not restrict the lines spread. On the contrary a longer bridle, for sure, will make the opening time longer because of the longer distance needed to stretch the parachute.

Where is the correct compromise? Out of 276 openings that I know with Metamorfosi chutes, I know of one case only where the parachute got tangled: the glider was spinning very fast but coming down quite slow and the pilot was not able to throw the bag. The bag fell down, the parachute came out correctly, but below the glider, and got tangled while moving up (the pilot landed on flat ground uninjured). It would have happened the same regardless of the kind of deployment bag or bridle length. Actually, in a similar situation, an American pilot managed to get two parachutes tangled: both packed in an envelope (landed in trees and survived).

"Melting Point of Nylon. Nylon does not melt at 200°F. It melts at 480 to 500°…"

I agree Nylon doesn't melt at 200°F because I intended 200°C. Sorry I forgot to make the transformation in Imperial Units but you could expect a non American was not using Fahrenheit :-) As a matter of fact melting point of a solid block of Nylon is between 230°C and 250°C (446-500°F) and softening point is between 180°C and 210°C (356-410°F) depending on the kind of Nylon.

When speaking of fibres things change slightly and, for Nylon ropes, Marlow (http://www.marlowropes.com/yachting/material.htm) gives a melting point of 210°C (410°F). Line length can be duplicated well within tolerance of course, but will it remain within tolerances? Nylon stretches and shrinks quite a lot with temperature and humidity and my experience says its behaviour depends on the batch too. Still it's possible to make a reasonable good job, but I would just prefer a parachute where it's cheap to replace the whole set of lines.

V-Tabs Just because you have v-tabs on your parachute does not mean they are going to do the job especially if they are sewn to the outside of the parachute! Looks like they do the job. Possibly because they are in between two rows of Kevlar?

"Paraswivels have been very effective in stopping parachute lines from winding up and closing the parachute as the wreckage rotates. The rotation of the broken hang glider has nothing to do with parachute design."

I partially agree but my opinion is somehow different. If you are interested have a look at (https://OzReport.com/toc.php?Ozv6n27.shtml)

"Much of my information comes from over 20 years of first hand hang gliding accident reports involving parachutes…"

My one comes from 26 years of first hand experience. Does that mean I'm 30% better? :-( :-(

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Betty on parachutes

Sat, Jun 14 2003, 2:03:06 pm EDT

accident|altitude|Betty Pfeiffer|bridle|equipment|G.W. Meadows|harness|history|job|nylon|parachute

Betty Pfeiffer<BettP@aol.com> writes:

Deployment bag verses Diaper Controversy

Deployment issues have been studied throughout the history of parachutes. In the 1970's G.W. Stevens of Great Britain developed anti-inversion netting in an attempt to reduce round parachute malfunctions.

A byproduct of extensive testing by US and British troops on anti-inversion netting revealed the importance of controlled deployment sequence.

Parachutes were tested using a variety of deployment systems including Deployment bags, Diaper systems, "Banana-Peel" Bags, Deployment Sleeves, and Skirt Hesitator Quarter Bags to name a few.

The results clearly show that the deployment bag kept the deployment sequence organized far better than the other methods resulting in consistent deployments with fewer malfunctions.

For our application, with a high risk of entanglement, a properly designed deployment bag protects the parachute from snagging on the wreckage, can allow the pilot a second (or third) throw if he/she did not clear the wreckage, maintains the momentum of the throw since only the required amount of parachute snakes out of the deployment bag, and keeps the parachute organized so chances of malfunctions are reduced.

Systems that allow parachute components to "dump" into the air to various degrees, such as diaper systems, risk tangling with the wreckage, out of sequence deployments which can cause temporary partial inversions, canopy inversions, line over situations and other problems.

Once the parachute is in clear air with a suspended weight, it will want to organize itself. In the process friction can cause heat, which can cause damage.

The process of organizing itself will give the parachute system a greater rate of descent than when it finally stabilizes.

Last month a HG pilot threw his emergency reserve packed in a "diaper". It took him 1500 feet of altitude loss untangling lines so the parachute could open. Fortunately the pilot had the presence of mind to stay on task and was able to land safely under a full parachute minus 2 lines. It is even more fortunate that he had the altitude to deal with the tangled mess.

Parachute Bridle Issues

When a hang glider tucks, tumbles, spins or breaks we cannot be sure of what position the pilot will be in when he/she throws the parachute. We do know that the chance of the parachute bridle coming into contact with the pilot or wreckage is likely.

Bridle Length

Too many pilots have experienced the consequences of bridles too short to clear the wreckage of the hang glider. The 15-foot bridle has lead to at least three pilots impacting the ground with the parachute streaming behind (one hip replacement). Even with longer parachute bridles, pilots have watched in horror as the bridles have tangled in the wreckage sometimes barely managing to get the parachute into clear air.

If you take the measurement from the carabineer to your parachute container on your harness under the control bar then to your furthest wing tip and your bridle is that length or a little longer, you have helped reduce the risk of your parachute not clearing the wreckage.

Our standard parachute bridle is 25 feet long. By shortening it to 15 feet we only increase the risk of the parachute not getting into clear air.

Use of Line Sleeves to Extend Effective Bridle Length

The use of line sleeves is analogous to a slider used on parachutes. It slows parachute inflation by restricting the line spread. In addition, if the line sleeve contacts broken tubing or other sharp objects during deployment, you risk damaging the lines inside the sleeve. If the line sleeve gets hooked on wreckage it is conceivable lines can remain hooked and distort the parachute on opening.

If the parachute line length is too short i.e. the effective line length has been reduced by the "bridle bundle", access to the air channel can be restricted and slow down inflation.

If we look at the importance of shortening the bridle 5 feet verses the consequence of increasing your risk of not having an open parachute, the design decision is obvious.

Melting Point of Nylon Nylon does not melt at 200°F. It melts at 480 to 500° and slightly yellows at 300° when held for 5 hours.

Parachute line Replacement

A competent rigger can easily replace parachute lines sewn directly to the parachute. You do not have to throw away the whole parachute if you need to replace a damaged line. Line length can be duplicated well within tolerance. On a properly constructed parachute you will not loose strength with a line replacement.

V-Tabs Just because you have v-tabs on your parachute does not mean they are going to do the job especially if they are sewn to the outside of the parachute!

Paraswivel

Paraswivels have been very effective in stopping parachute lines from winding up and closing the parachute as the wreckage rotates. The rotation of the broken hang glider has nothing to do with parachute design.

In conclusion:

Much of my information comes from over 20 years of first hand hang gliding accident reports involving parachutes, years of involvement with the Parachute Industry Association, our testing of various parachute designs and well respected parachute design sources.

I have always believed that we should not reinvent the wheel but learn from other similar industries. I also believe that we don't have to wait until someone gets hurt or killed before we can recognize a potential problem with a system.

At parachute clinics I teach how parachutes work and have pilots apply that information to how their parachute is constructed. There are some construction techniques that are "unconventional" and others that are just plain scary.

In a society of extremely powerful marketing minds, pilots really need to understand and agree with the philosophy behind the design of their life saving equipment.

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Angelo responds re: parachutes

Sat, Jun 14 2003, 2:03:05 pm EDT

advertising|Angelo Crapanzano|bridle|certification|cost|DHV|equipment|glide ratio|Juan Lara|nylon|parachute|Rob Kells|safety|site|Wills Wing

Angelo Crapanzano <angelo@metamorfosi.com> writes:

It almost looks like Rob Kells felt my article as an attack to the Lara. :-( :-) I'm really sorry because it was, not at all, my intention: I do consider Wills Wing a true safety conscious manufacturer and the Lara a safe parachute.

I do agree with Gary Douris on everything. What I actually wanted to point out is that a good diaper pod could be as good as a good envelope one, and there could be quite bad envelope or diaper designs.

The debate between diaper and envelope is worthless. What really counts is to have an exactly staged deployment sequence: bridle-lines-canopy, and a pod which holds firmly the parachute until you throw it but opens and lets out the canopy easily. This could be achieved (or not…) both with a diaper or an envelope. The other differences are, in my opinion, more a matter of tradition and philosophy than practical ones.

I mainly wanted to push pilots to test the reliability of their equipment (as explained in my previous mail) and to check if their pod works good (regardless if it's a diaper or an envelope).

I agree with Rob Kells too: Kevlar or Spectra significantly reduce bulk and weight but increase the price. Cost is important but (as Rob says) "the lowest cost is not at the top of the list in decisions we make on emergency reserves" too. For example, since 1982 I use Kevlar on Metamorfosi canopies while the Lara Gold uses Spectra and Kevlar on lines and bridle. Lara and Conar parachutes are simply quite different designs and require different solutions. It is not mandatory that one is good and the other is bad… even if I believe my one is better… while Rob and Gary, I'm sure, think the contrary :-) :-)

I have to apologize if my English was misleading: what I wanted to say is that, given the same parachute design, the use of Spectra or Kevlar increases the opening shock, thus reduces the "strength" of the parachute (considered as the maximum acceptable speed). This lower maximum speed could be perfectly acceptable for our use, or a slightly slower opening time (for example using more porous fabric) could counterbalance the loss of strength. In this example the use of a more porous fabric would increase the sink-rate, thus one would need a bigger area and more bulk (which could be higher or not of the one saved using Kevlar lines and bridle) to get the same performances. It is just a matter of compromise and it's even possible to get similar results with very different designs.

For sure it was not my intention to say that a Kevlar bridle would break and a Nylon one will not. I'm sorry if I could have been misunderstood. I just wanted to point out that, because of the reduced elasticity of a Kevlar bridle, there need to be something to compensate in the parachute design to get the same parachute "strength".

Of course, as Rob says, both a properly designed Kevlar or Nylon bridle, likely, would not break: since the one inch tubular webbing disappeared from the market I heard of very few cases of a bridle failure (possibly due to uncoated cables?). Still people must know of the problem because there are too many obsolete parachutes around and many bridles which are not properly protected from sunrays which, regardless if they are in Kevlar or Nylon, should be replaced.

I also agree with Rob about the DHV test: it leads to bad deployment bag design (regardless if they are envelope or diaper…). This test is made letting fall a dummy and the deployment bag at the same time, from 60 m high: the parachute has to open before hitting the ground. To pass this test it's only important to add drag to the deployment bag and to let out the canopy as soon as possible. This is not exactly what we need in a true emergency with a broken glider!

I agree the ultimate test is: "at what speed has it been tested without failure?" The Lara has proven to be good and, for example, the Conar 18 has been certified throwing it from an airplane at 150 km/h (93 mph) with 100 kg (222 lb) load, and tested without failure with 80 kg (178 lb) load, after a free fall of 150 m where it achieved 180 km/h (112 mph). Again, Lara and Conar are two totally different design but both proved to be strong enough.

I also agree that descent rate tests of parachute have a great deal of scatter and some manufacturers declarations are well beyond reality: I still remember the Cyclon (an English manufacturer's hang glider from 1978) was declared to have 14 of glide ratio, like a modern topless glider! I've also seen parachutes with 28 square meters of fabric declared as 35 :-( By the way, I have made lots of accurate sink-rate tests and in my web site I do declare for my Conar parachutes about 5% worse sink-rate than what officially measured during AFNOR certification.

As Rob says "any emergency reserve system that saves a life is a good one" but I'm sure he doesn't mean any parachute is a good one. As with everything there are several good, many acceptable and, unfortunately, some bad ones. It is up to the pilots to make the choice and to the manufacturers to give correct information, not just advertising.

I'm glad to hear there have been more than 400 saves with Free Flight parachutes because, added with the 276 reported saves with Metamorfosi parachutes, makes quite a lot of happy… and still alive… costumers :-)

Well Rob, up to now it looks like we practically agree on everything… maybe except the way to skin the cat? :-) :-)

Rob you're right: I don't know of any malfunction which could be clearly in relation with the swivel at the junction between lines and bridle but, in my opinion, there could be problems, at least in theory and in some particular cases, with this setting. Unfortunately this mail is already long (and tiring for everybody) enough. Moreover to explain what is the problem would take some time and I would like to make it clear; please could you wait a couple of days?

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Other parachutes

Thu, Jun 12 2003, 2:03:02 pm EDT

Angelo Crapanzano|Betty Pfeiffer|bridle|cost|DHV|equipment|Ernie Camacho|Europe|exhibit|FAA|landing|military|nylon|parachute|PG|release|Rob Kells|Roy Haggard|safety|sport|Wills Wing

Gary Douris <gary77douris@yahoo.com> of Free Flight Parachutes writes:

Addressing the letter from Angelo Crapanzano (https://OzReport.com/toc.php?Ozv7n132.shtml#7)

His seven points for a good deployment bag are right on. As he guessed, it is only his feeling that a four-flap diaper is better than an envelope type deployment bag that I disagree with.

The best way to deploy a parachute is to have it extracted from the container by some method attached to the apex. It must have the skirt contained until all the lines are extended and there is tension on the whole system. Because this sequence is not possible with a hang glider deployment, some other ideas had to be used.

More than 20 years ago, Free Flight's Ernie Villanueva used his skydiving and rigging experience to develop the deployment bag with a side pouch for line stowing. The canopy was secured in the bag with 2 line stows and the lines were secured with 2 stows of the bridle.

When Angelo's diaper is deployed, the bridle goes first followed by the lines. When the diaper is opened the canopy is left sitting there all nice and neatly folded just like it was in the diaper. It must now unfold then deploy.

The envelope system we use does one thing that the diaper does not. When the envelope is deployed, the bridle goes first followed by the lines. Then the canopy unfolds and is more or less straight lengthwise and then deploys.

This is the best of a world which is not perfect due to the cables, tubing and such that can catch a canopy on its way to a good deployment leading to a nice safe landing.

I commend Angelo on his letter, I should have written it myself.

Rob Kells <Rob@willswing.com> at Wills Wing writes:

I'd like to address a few comments contained in Angelo's most recent letter on parachutes, and offer a few of my own.

A little background: Since 1978, Wills Wing has sold parachutes designed and manufactured by Free Flight, and thus we have a clear bias. We have always trusted in their design expertise and build quality. They have been manufacturing FAA certified skydiving parachutes for more than twenty-five years.

Envelope Deployment Bags vs Diapers

There are two different deployment systems commonly used for hang gliders, and as you'd expect, each has advantages and disadvantages. The Envelope provides a more secure stowage of the paraswivel, and a more staged deployment, but requires regular rubber band maintenance, while most Diaper bags do not.

The DHV drop test that is done from a bridge favors the Diaper bag because it can be packed in such a way as to require a very low pull force on the bridle to release the lines and parachute from the bag. The Envelope bag does not do well in this test because there are four separate stows to undo before the parachute can deploy, compared to one on most Diapers. Because most of Europe follows the DHV testing methods, it is logical that most European pilots are flying with the Diaper D-bag instead of the Envelope type commonly used here in North America.

Both Envelopes and Diapers are designed to get the parachute clear of the wreckage, and if properly packed, both systems accomplish this objective. The market here in the US has chosen the Envelope type system for two main reasons. First, between the two of us, Betty Pfeiffer of High Energy and I have done the majority of formal parachute deployment seminars in North America. We both believe in the Envelope system. We saw many more Diaper equipped parachutes fall out on the floor below the pilot when an attempt was made to throw it in a practice deployment than Envelope equipped parachutes. This was usually the result of the closing stow being too loose.

We have also seen a number of Envelope systems exit the bag prematurely when the rubber bands were old. In recent years changes such as relocating the deployment handle so the force of the pull and throw did not load the rubber bands directly, and using a double over flap at the opening end on the Envelope, are design improvements that have made the condition of the rubber bands much less critical.

Kevlar and Spectra vs Nylon

It's true that Kevlar and Spectra have much lower stretch than Nylon. It is not true that an emergency reserve must have a slower opening time to exhibit an acceptable opening shock. It depends on the construction of the parachute.

If we were to use it as a sport parachute that was designed for repeated openings, the Kevlar/Spectra blend would not be appropriate. But let's remember what the design purpose is. If you are unlucky, you may deploy your reserve once in a lifetime, if you are careless or stupid, maybe a few times in a lifetime of flying.

Roy Haggard designed the LARA (Low Aspect Ratio Annular) for the US Military, and licensed Free Flight to built it for Wills Wing to sell in the HG/PG community. The LARA (Nylon Type 18, 6000 pound bridle, with nylon lines) was repeatedly drop tested from an airplane at speeds up to 90 knots without failure.

FFE's Ernie (cited in Gary's letter as the designer of the original Envelope deployment bag) has jumped the LARA from an airplane at 90 miles per hour a number of times, again without failure. Next came the LARA Gold, which was also drop-tested from an airplane without failure. We choose to name it "Gold" because the Kevlar bridle and Spectra lines added significantly to the cost.

The important point is that using Kevlar and Spectra reduces the weight by more than 1.5 pounds, and the pack volume by about 35% giving you a very light weight, small pack volume with a large parachute, and it's associated slow decent rate. The Kevlar bridle is a woven flat 6000-pound webbing that, because of the weave, has some stretch. I'm not sure if it is because English is Angelo's second language, but his historical note regarding pilots breaking cable hang loops in the 1970s seems to imply that pilots can expect to break Kevlar parachute bridles.

In the real world, the ultimate test is: at what speed has it been tested to without failure? Does the opening shock fail the parachute, or not? I am not aware of any structural failures on FFE emergency reserve.

I agree with Angelo that a one-inch tubular bridle is not acceptable. We know of several cases when parachutes with one-inch tubular bridles were cut away on deployment. Free Flight has used a minimum of one inch Type 18 flat 6000-pound material since the early 1980s, with no cut-aways that I'm aware of. I also agree that a Kevlar bridle is less subject to being cut by heat from friction because it has a much higher melting temperature.

Speaking of Swivels

Angelo does not make it clear why he writes about 'swivels that "they should not be put near the junction between lines and canopy, but this is another story :-)".

The implication here is that there is a problem with paraswivels, so please tell us this story. I believe that the majority of hang glider reserves sold in the US for hang gliding utilize a paraswivel, while most sold in Europe do not.

There have been several instances that we know of where a spinning glider twisted the bridle so many times that eventually the shroud lines also twisted and closed the parachute. Wills Wing felt so strongly that the swivel was a necessary piece of safety equipment, that we bought the US patent to make them in volume, so as to reward it's inventor, reduce the cost, provide them as standard equipment on all HG reserves, and of course to sell more of them.

The 'swivel is mounted just eighteen inches from the lines. All the airplane drop tests and hundreds of real world emergency deployments have not shown any problems with this mounting location. We do not want the 'swivel on the pilot's end of the bridle, because if the bridle gets caught on spinning glider wreckage between the 'swivel and the parachute, it cannot serve its purpose.

Virtually all-skydiving canopies utilize hardware to attach the lines to the risers, so I'm very curious what information Angelo has as to why this mounting location is a problem. We have made over one thousand 'swivels. The only problem I am aware of was with a batch that was made with the setscrew hole not drilled deep enough in the barrel.

For more information on the advisory issued in May 2000, see any of the parachute pages at www.willswing.com

Just as Angelo could use our ideas if he thought they were better than his own, we could use his. If we found that his deployment bag, materials used in the bridle, or lack of a swivel was a better way to go, that's what we would be selling. In all three examples it would be less expensive to manufacture, but the lowest cost is not at the top of the list in decisions we make on emergency reserves.

For more information on the LARA reserve see: http://www.willswing.com/prod2.asp?theClass=parachutes&theModel=lara

Descent rate data FFEs drop test data has a great deal of scatter. The descent rates range from 14 - 19 feet per second. We publish (what we think is) a conservative number of 17.5 feet per second for the LARA.

To put the performance data you find on manufacturer's web sites in perspective: in the early 1980s we stopped publishing glider performance data, because regardless of the real numbers being achieved, some manufacturers published performance data that was well beyond reality, just to sell more gliders. (Imagine that :')

As the saying goes "there's more than one way to skin a cat". Any emergency reserve system that saves a life is a good one. There have been more than 400 "saves" with Free Flight parachutes.

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Parachutes »

Wed, Jun 11 2003, 2:03:05 pm EDT

advertising|Angelo Crapanzano|bridle|Europe|harness|magazine|nylon|parachute|PG|safety

Angelo Crapanzano <angelo@metamorfosi.com> writes:

I've gotten some emails congratulating the article on deployment bags (thanks a lot to everybody!) and asking some more info about rescue parachutes.

In particular there was an interest on bridle and lines length. They did wonder how is possible to have bridle+lines shorter than the sum of the two. :-)

At the beginning of parachutes, it was common to define the parachute size by the number of lines. This is now wrong because parachutes of different design could have gores from 60 to 180 cm (2 to 6 ft) wide, which will make quite a difference in parachute sizes, still having the same number of gores!

What counts in a parachute is the actual projected area (not easy to calculate) and the shape and design of the canopy (not so easy to judge).

Right now most manufacturers of HG and PG parachutes declare the fabric area, which gives quite a good idea of how bulky a parachute is (but, unfortunately, many declarations are quite wrong) but it's only good to compare parachutes of the same design but different size. Unfortunately it tells very little while comparing parachutes of different design.

One of the most important characteristics of a parachute is its sink-rate. To give a physical idea of a parachute sink- rate I do prefer to quote the "equivalent height" which is the height of a jump equivalent to the sink-rate under canopy.

Knowing the sink-rate it's quite easy to calculate the equivalent height (with a bit of approximation):

EqHeight = Sinkrate2/20 (sink-rate in m/s and result in m)

(For those interested in mathematics it comes out from the equation between kinetic energy and potential energy).

It is much easier to visualize that, coming down under canopy, would be like jumping down from 1,5 m high (5 ft) than to say your sink-rate would be 5,42 m/s (1076 ft/min).

Another advantage of using the equivalent height is that makes things linear instead of having square roots involved:

• jumping down from 2 m height you'll hit the ground twice as hard than jumping down from 1 m

• doubling the load under the same canopy, the equivalent height doubles

• using a parachute of the same design but double area, your equivalent height would be half and the opening distance, reaction times excluded, would be 1,41 times longer… sorry one square root is still there :-)

Just for your knowledge, opening distance (to be more correct "filling distance") is the distance needed for a parachute to open in ideal conditions, from lines stretched to fully open parachute.

Filling distance depends on parachute design and size; it's independent of speed (unless at very low airspeeds where a smaller and lighter parachute gets probably an advantage) and, given the same design, it's linear with parachute diameter.

Opening distance is much more interesting for us than opening time because, when we toss a parachute in a real emergency, we are not really interested in how much time it would need to open… but if it would open before we hit the ground!

Sink-rate depends on parachute size only for parachute of same design. Parachutes of same size and different design have not the same sink-rate, as much as an old Rogallo glider of 14 square meters has not the same sink-rate of a modern topless glider of same surface.

Just to give you an idea, at the test made by Vol Libre Magazine, the Conar PG18 (28 m2) was the smallest parachute tested but did show the best sink-rate (4,8 m/s with 97 kg pilot's flying weight). The only other parachute to match this sink-rate was 43,4 m2 (i.e. 55% bigger).

Advertising corner :-)

If you want more info on parachute performance comparison have a look at www.metamorfosi.com/compara_en

Let's go back to the lines:

The first HG parachutes had as low as 10 lines (one every two panels) to make cheaper and lighter parachutes, but definitively weak ones; fortunately, they disappeared quite soon from the market.

Generally speaking, given the same canopy, more lines means a better shape of the canopy and a better sink-rate but, of course, with more lines there is an higher chance of a line getting tangled. A compromise, like always, is mandatory. Consider that the more the lines the bigger the bulk and the higher should be the safety margin on each line because of possible overloading.

Lines and bridle must absorb the opening shock. On round parachutes they are usually made in Nylon because it has a good strength and a very good elasticity under load. Very strong fibres (like Kevlar, Spectra or Dynema) are very good in absorbing static loads but not so much for shock loads. (Spectra and Dynema are practically the same fibers with a different name, one in US and the other in Europe).

Let's make a, very simplified, example to find out the different behavior between Spectra and Kevlar or Nylon, letting fall a 10 kg load (22 lbs) attached to a 5 m rope (16 ft).

After 5 m of free fall the load gets a speed of 9,9 m/s.

• If the line is in Kevlar or Spectra the elasticity is about 2% (10 cm elongation for a 5 m rope). This means we have to stop the load within 10 cm and, with some calculations, we get an average load of 50 g but, actually, the peak load would be higher (which means, with a margin of safety, we need a Kevlar or Spectra rope of 1000 kg).

• If we use a Nylon line instead, the elasticity could be over 15% which means it has to stop the load within 75 cm. The same calculations bring to an average load of 6.7 g only (with the same margin of safety a 135 kg nylon rope would be enough).

Of course in these calculations we did consider the rope attached to a solid stiff body (like to make the test tying the line to a bridge), not a parachute. Nevertheless we see the advantage of using nylon, both in lines and bridle, to control peak shock loads. Of course it's possible to design a good parachute with Spectra lines but, to get an acceptable shock load, it needs to have a slower opening time (i.e. longer opening distance).

Just an historical note: this is the reason why steel hang loops, quite common in hang gliding up to 1977, disappeared after provoking several fatalities.

Unfortunately Nylon, especially under tension, is easily cut when sliding against a cable. This happens because the friction heats up the Nylon which melts at about 200°. Spectra is not better, but Kevlar is definitively resistant to wear and burns at over 500°. A well dimensioned Kevlar bridle would likely survive any sliding against a cable but will significantly increase the opening shock too because Kevlar has almost no elasticity.

Tubular webbing, quite common in old parachutes, is dangerous and very likely to cut sliding against the cables and there are several stories (some funny, most sad) to prove it. The normal solution is to use an over dimensioned webbing or, better in my opinion, a braid bridle. Compared to a webbing, a braid bridle is less likely to break against a cable and, because of the different construction, has the advantage of being more elastic too. Of course there is a disadvantage too: it's thicker and less aerodynamic.

Please remember that the first meter of bridle stays outside of the parachute container and must be well protected from UV rays while the eye to connect the bridle to the carabineer must be protected against abrasion too. A good UV protection is important for the whole parachute too because a parachute is like a chain: it is only as strong as it’s weakest link. If something is not protected from UV rays or is damaged, the whole parachute will lose strength.

Be careful: the harness parachute container often is not good enough to protect the parachute, while protections or deployment bags covered with a deposit of aluminum powder, are often more a selling argument than functional. Here’s a test: have a look at the sun through your deployment bag material and check if the light passes through…

Rescue parachutes lines could be directly sewn directly to the canopy or could be connected with a knot like on parachuting or paragliding. Lines sewn directly to the canopy are definitively cheaper but, in case one is damaged, you practically have to throw away the whole parachute. Technically it would be possible (only by the manufacturer) to unstitch and replace the line with a new one, but results could be dangerous: how can you be sure the new line is (or better will be) as long as the old ones? Nylon stretches and shrinks quite a lot with temperature and humidity (up to 30 cm in a 5 m long line). It's not a real problem if all lines shrinks the same, but the only way to get it in a parachute, is to cut all of them from the same roll (including the apex lines) and, if one line is damaged, the full set of lines should be replaced (which is very easy and cheap to do in those parachutes where the lines are knotted to the canopy).

If lines and apex line are made with different rope dimension (or, even worse, with different materials) there could be a problem of different shrinking. If the apex line gets longer the parachute would have a worse sink rate, while if it gets shorter it may become unstable. When packing your parachute check the respective length of lines and apex line did not change from the original setting; if in doubt ask the manufacturer (just to avoid tons of mails, in the Metamorfosi Classic the apex line must be slightly longer than the other lines while in the Conar both apex and gore lines have the same length).

The connection between lines and canopy is quite important: it's important that the line is sewn for a long while over the canopy (much better if it goes continuously all over the canopy) and is almost mandatory that the connection between line and canopy leading edge is reinforced with a V tab (other good systems could be acceptable but the V tab is the best known).

Speaking about lines and bridle length we have:

- a long bridle is useful to reduce the chance of the lines getting tangled in the wreckages.

- long lines are useful to better absorb the opening shock and to get a better sink-rate, given the same canopy, because of a bigger projected diameter.

- a short sum of lines + bridle is useful to get a faster opening time.

At first, it looks like a compromise is necessary but there is a simple (and clever) workaround: in my parachutes the "bridle" itself is about 5 m (16.5 ft) long and the lines about 5 m too, but the first 2 meters (6.5 ft) of the lines are covered with a lightweight fabric sleeve. This means during deployment, when you need a long bridle to get the lines clear of any spinning wreckage, the "bridle" is 7 m (23 ft) long (i.e. longer than the standard 20 ft American bridle) and the lines 3 meters (10 ft) only to reduce chance of tangling but, once the canopy opens and such a long bridle becomes unnecessary, the sleeve slides down (or breaks at high speed) and leaves the long lines free.

Metamorfosi parachutes have, in practice, a 7 m (23 ft) long bridle and 5 m (16.5 ft) long lines but the sum of the two is 10 m (30 ft) only!

Please note a long bridle is not mandatory after the canopy has opened because it's enough to have the bridle almost as long as half the span to avoid any chance of a tangled line; moreover, after the canopy has opened, there are much less chances of a line getting tangled and any spinning of the hang glider will slow down substantially.

Speaking about bridles, just a quick note on swivels: depending on parachute design they could be useful or not but, for sure, they should not be put near the junction between lines and canopy… but this is another story :-)

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Aerotow paragliders

Sun, Jun 1 2003, 2:03:03 pm EDT

aerotow|altitude|bridle|David "Dave" Glover|David Glover|drogue|electric|government|harness|job|Lighthawk|Mark "Forger" Stucky|Oz Report|payout winch|PG|power|powered|powered PG|PPG|Quest Air|sailplane|Stuart Caruk|Stu Smith|tail|technique|tow|towing|trike|tug|winch

Mark Stucky <stucky_mark@hotmail.com> writes:

I just noticed the discussion on the bigair paragliding forum regarding the recent paraglider aerotowing shown on the Oz Report. For several years I've occasionally put thought into the conceptual design for aerotowing a paraglider. I really think the future is in aerotow and discussed the issues some with David Glover (who is also very interested in it for big meets) last September at the Tehachapi sailplane fly-in. I wish we could have talked more but most of my attention at the time was dedicated to the Lighthawk flying debut.

The obvious issues with aerotowing are the slow flying speed of a paraglider and the relatively small amount of pitch and airspeed control available. Some comments on the web about concerns with the vertical distance of the canopy from the tow point are not that big of a deal due to the low thrust and drag forces involved. After all, if a paraglider couldn't handle 80 lbs of thrust near the CG of the pilot then powered paragliders would not work either!

I see three methods for aerotowing a paraglider.

Method 1: The obvious solution is a tug that tows at a compatible speed and climb rate. This method would involve conventional "follow the tug" procedures and a fixed length of towline. While having a PPG or powered PG trike arrangement has some appeal due to their slow flying speeds, I think they will cause more problems than they solve. I think a better tug would be a fancily flapped ultralight or a very large yet lightweight hang glider trike. Until such an exotic tug is designed we will have to make due with exotic procedures.

Method 2: Perhaps the best solution for paraglider aerotowing is to make a lightweight payout winch that can handle 2500 feet of spectra. Until we can get the tow airspeed slow enough to match the speed the paraglider pilot would like we will need to figure out how to handle a speed differential. With a payout winch you could use existing tug aircraft with procedures similar to a ground payout winch tow, the paraglider could simply climb up behind the tug without regard to maintaining the same relative altitude as the tug.

Let's assume we can get a tug that can tow at 45 feet/sec (30 mph) and have a paraglider that wants to fly at 30 fps (20 mph) for a differential speed of 15fps. I think a comfortable climb rate for a paraglider from a ground tows is 500 fpm. If the tug was also climbing at 500 fpm then the total climb rate of the paraglider would be 1000 fpm so a two minute tow to 2000 feet AGL would require 1800 feet of tow line (plus whatever amount you initially laid out). The benefit of an aerotow winch would be that you could use a small field and any wind direction instead of being tied to a long road.

Additionally, the tug could tow you to a thermal although once the line pays out beyond a few hundred feet the tug will be limited to shallow banks or short, quick turns (similar to ground circuit towing). The winch would have to have some kind of rewind capability and a small drogue to ensure it couldn't recoil into the tug's propeller.

Method 3 is obviously not for the faint of heart and requires advanced skills at both ends of the towrope. It is designed to make due with existing tow aircraft and uses a small fishing reel as a short duration payout winch. One way to manage a small speed differential is by using differential bank angles to fly concentric arcs with the paraglider flying a slower speed on the inside of the turn.

Stu Caruk's comments about delivering a bag of goods from a Cessna by hanging it out a window and flying circles around it has some merit. I was once involved in a government program that built upon that technique in an attempt to hover a small spy package several feet off the ground. The package contained sensors and fed position and altitude information back to the aircraft that was equipped with an exotic hydraulic winch which would make the fine high speed in/out corrections to the tow line while the pilot make the rough corrections by following guidance to fly an exact arc thousands of feet overhead. The program got cancelled and I sure wish I could have figured out a way to get my hands on the winch and the 10,000 feet of spectra!

To tow successfully without a high capacity payout winch, we need to manage not just the airspeed but also the climb rate, turn rate, and rope length. To manage the rope you need to first start with the proper length of towline. Too short of a rope and the workload is too high, the allowable lateral/vertical errors too small, and the probability of a lockout is too high. If the rope is too long then the turn circles are no longer concentric and havoc will quickly result.

We need to fly the proper arcs at an angle of bank that does not require extraordinary piloting skills or decrease the climb rate excessively. This means we need shallow bank angles so we can increase or decrease them as required without generating excessive turn rates that would be impossible to manage in a tethered relationship.

Successfully aerotowing a paraglider with this method requires a change to the traditional paradigm of towed flight in which the glider must dutifully follow the tug. Both the paraglider pilot and the tug pilot will have to abide by a pre-coordinated plan for dealing with the continuous corrections that will be required. In the absence of such an advanced plan, the aerotow will be short-lived.

If our 45fps tug flew at 13° bank then his radius of turn would be 275ft at a leisurely turn rate of 10° per second. To achieve the same turn rate with the 30 fps paraglider, it would use 9° of bank for a radius of turn of 178ft. At these conditions I computed a 160 ft towrope as optimal. Under these conditions the paraglider is approximately 45° off axis from the tug (i.e. with both aircraft in a left handed turn, if the paraglider is pointed north, the tug would be pointed northwest).

While this would normally be disconcerting to a tug pilot used to conventional aerotows, it is possible to tow with the line leaving the tug at a 45 degee angle (and only 70% of the tow tension providing thrust to the paraglider). As always, though, the paraglider pilot should strive to keep the towline square to the harness and canopy. Note that if the towrope was routed to the tug's tail then the drag of the paraglider would always be trying to pull the tail inline with the glider and the tug would have to have sufficient rudder power to counter the torque of the off-axis tow or else have some sort of CG/bridle hook up.

If both aircraft are climbing out at the same rate then everything is perfect but chances are there will be some errors. Here is where the pre-planning is required. If the tug is climbing faster than the paraglider, then the paraglider should decrease its bank slightly to increase its speed and climb rate. If the paraglider is climbing above the tug (more likely) he should increase his angle of bank to cut to the inside. Here is where a smart tug pilot will make or break the tow.

He needs to evaluate if the paraglider pilot has been doing a good job and if it has room to make the required correction. If the paraglider is slightly out of position but correcting back then the tug may just observe. If the paraglider pilot is already in the planned position (about 45° inside the turn) then there isn't much more he can do and the tug pilot should either throttle back or increase his bank angle to decrease the climb rate. His course of action should be based upon his interpretation of the paraglider's 3-D position and heading (if the paraglider has dug far inside the turn and the tug turns harder then the paraglider will have to deal with a huge change in heading and possibly even slack line).

If the plan is properly coordinated and well flown by both pilots then a small payout winch could be mounted on the tug. The purpose of the winch would be to handle short periods of excess tow pressure. The winch could simply be a large fishing reel with some pretty small towline (or large fishing line - depending upon your point of view). I'm not a fisherman but I think you could get a commercial product with 500 feet of line that only weighs a few pounds.

You would set the drag for say 20% more than the planned tow force and it could handle short periods of time while the aircraft are transitioning back to the proper positions to reset the planned steady-state conditions. A small electric motor could wind the line back in at the completion of the tow. The reel should be mounted in the field of view of the tug pilot and the line could be routed through guides or pulleys to route it clear of the propeller.

(editor’s note: I believe that all of these methods are being looked at and attempted in some cases at Quest Air.)

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Tumbling my Topless Sensor

Tue, May 27 2003, 2:03:01 pm EDT

Bob Trampenau|bridle|dust devil|Florida|landing|parachute|safety|Seedwings|tuck|tumble

Tim Locke <tlocke@optonline.net> writes:

I am the pilot with the dubious distinction of tumbling May 18th at Mt. Greylock, Massachusetts. I have been hang gliding for 29 years and have had my fair share of turbulence and getting dumped. It was a rude awakening without warning to be pitched over and under in a series of 3 tumbles. They were so rapid that I had no recollection of doing them.

Ended up at the trailing edge/keel in a surreal moment of watching my Sensor 142 topless glide along upside down with me trailing like swimmer on the transom of a boat. Just previous I had climbed 2000 feet in two minutes after hooking a powerful thermal coming off the spine of this 3000ft mountain.

I had cored it without any hint of serious thermal shear in my short lived flight of eight minutes. Closing in on Tom Nejame overhead I started scanning to catch a glimpse of him. As I reduced my left hand bank angle to shift my circle I was pitched violently over.

From Tom's description of my right wing going down as I went ass over teakettle, it would appear as if I had found the edge of a nasty swirl of air. His next description of me is seeing my undersurface with arms extended. I have known for years about keeping your weight forward, but in spite of his criticism I had no time for even a knee jerk reaction like pushing out. Thank you Davis for confirming that in your experience.

I had been climbing at up to 980 fpm and my vario registered 1920 fpm sink. That would be a 30 mph. differential at the interface of the thermal. Maximum registered air speed was only 34mph. If I had just reduced the bank angle just as the right tip found the shear it could have lead to the pitch over.

(editor’s note: I have invariably found that max values shown on vario logbooks are much higher than what I actually experience as there seems to be no dampening of the values by choosing a reasonable time period, like one second, over which to find an average value.)

It is perplexing as not all pilots complained of extraordinary turbulence. But some pilots did. A pilot on a cross country flight from Mt. Ascutney said he was petrified of going into the sail at any moment.

At Greylock there were some partial paraglider collapses and some other paragliders going on nice x-c's. There was a large sighted dust devil and a barn in Maine damaged by a dust devil. There was also height gains over 12,000ft that day. But apparently we have to rule out the atmospherics, as a recent post has leveled the finger at Seedwings for the incident.

I am not ruling all possibilities, but let’s not jump to conclusions until all the facts are in. I admit I am biased because I have owned 4 Sensors. I recently put a new sail on that has more double surface, shear rib length and tip chord than its predecessor. Yes, it was not factory flown and I accepted that.

I put hours on it in Florida, found that the center of gravity had not changed to any degree and it had pitch pressure at speed (not only valid consideration). I cannot say if the sail change had anything to do with it. I will say that I believe that is up to the manufacturer to deliver a proven glider and will asking for that now for assurance. Bob Trampenau is very safety conscious and to rule out every thing he is checking the glider out and will be performing pitch tests.

The glider is built solid and survived the tumbles with no damage to the airframe or sail. The violence of the tumbles beat the washout system up and he thinks the negative g tests for all gliders is too low in light of what happened. I use the same cable braced washout tube configuration as others, and get this.

I bent a 1"tube to 45°, snapped a washout tube brace wire, and snapped both outboard heim joints in a downward motion. This was not done on landing as I had a very soft landing in the flexible droopy limbs of a hemlock tree. He has already e-mailed 5 modifications that he going to do as soon as he receives the glider.

I appreciate that he sews Kevlar in the trailing edge as the parachute bridle did not cut into it. Seedwings takes a lot of heat for a small company that engineers a nice wing. Have not tumbles occurred on other popular wings. Much doubt could be dispelled by providing the test rig documentation. Let the facts speak and let’s continue addressing tumble/tuck issues.

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Deployment bags

Thu, May 15 2003, 3:00:07 pm EDT

Alessandro "Alex" Ploner|Alex Ploner|Angelo Crapanzano|bridle|Europe|Gerard "Gerry" Farell|harness|insurance|Laurent Thevenot|parachute|Rich Pfeiffer|safety|spin

Angelo Crapanzano <angelo@metamorfosi.com> writes:

Recently, while speaking about rescue parachutes, Alex Ploner told me in US there is quite a bad reputation for "diaper" deployment bags (flat pods with, normally, four flaps), while there is a good one for "envelope" ones (a bag normally opened on one side only). I already knew in US there was a preference for envelopes (while in Europe there is for diapers) but I didn't know it was so strong.

The deployment reliability of a rescue parachute depends mainly on the pod design; that's why I feel important to point out the differences between different concepts and, even more important, what makes a good or bad pod. I'm a manufacturer and of course my own design is my preferred one (otherwise I would make it different), but I'll try to be as general and objective as possible.

In a good deployment bag we need to have: easy extraction from the harness very low risk of accidental deployments, lines stowed inside the pod before deployment, ease of throw, very low risk of untimely opening, easy opening of the pod, staged deployment sequence.

1) An easy extraction may concern more the harness parachute container design than the pod itself. We need to have a big enough handle (remember it's always easier and safer to catch the handle using the thumb) and reachable with both hands (one could be injured or one hand could be better than the other in case of a spin).

The use of Velcro to keep the container closed is not reliable: often holds too little or too much. The Velcro should also avoided to keep the handle in place because if the pilot, at first try, peels out the Velcro but misses to catch the handle, then the handle could become unreachable (this is especially true in paragliding for dorsal mounted parachutes).

Be extremely careful there is not male Velcro on the handle itself: it may stuck on the lines loop holding the pod closed, thus impeding the opening. It's not only a theory: I've seen this happening during parachute clinics and, unfortunately, a German pilot died in Castelluccio di Norcia a few years ago, because of it.

There is one way only to know if your parachute is easy enough to extract: hang into your harness and try! Don't be too much surprised if you cannot get it out: during parachute clinics I've seen several pilots not at all able to extract their parachute.

2) Low risk of accidental deployments means the parachute must not come out by itself. The biggest improvement on this subject were the safety pins (introduced in the hang gliding world long time ago by Rich Pfeiffer) used at first as a safety for the Velcro but, if properly designed, are perfectly safe by itself. In some cases one could add an elastic or a sewing tread to hold them in position (check you are strong enough to break it pulling the handle!).

Be sure there is no way for the handle to get tangled in the side cables or in the base mounted instruments (there have been several accidental openings this way). Be also sure the pins are not too long (longer than the slack in the handle) otherwise there is no way to pull the parachute out of the container. Pins should be properly curved or flexible (straight pins could stuck if pulled in the wrong direction, as shown in several accidents) and be careful the head of the pin cannot pass through the loop (there have been several accidents this way too).

3) The lines stowed inside the pod before deployment are mandatory to reduce the chances of lines getting tangled into the wreckage (one line tangled is enough to get the parachute useless). Unfortunately there are several old pod designs where the lines are exposed.

4) The ease of throw depends on parachute weight but also in handle shape and length. A long handle makes it difficult to control the throw and could tangle on cables (some handles designed as an anchor don't certainly help). A handle attached to the pod in two points gives a more solid hold compared to the, unfortunately now common, single point attachment.

Never attach the pod to the canopy: to save some dollars in case of deployment, you definitively increase the risk of a tangled parachute!

5) Low risk of untimely opening means the deployment bag shall not open before you throw it and let it go. This can easily happen in an old style envelope pod where the handle is in the opposite side of the opening because only the elastics are holding the canopy inside the bag: if they are too old or weak the canopy will fall out before one throws it while, if they are too strong, the pod would be hard to open.

A good envelope pod design is to have both the handle and the opening on the same side, so the elastics don't have to hold the weight of the canopy. On some diaper pod designs the canopy or the lines can fall out if one shakes the pod (still holding the handle). In any case it's important to leave the right amount of slack in the bridle: the pod must not open until you let it go!

6) Easy opening of the pod is mandatory because, in case we cannot throw it forcefully (much easier to say than to do in reality), there is only the difference in sink-rate between broken hang glider and closed pod to open it. Please note that, in most common accidents, the closed pod falls faster than a broken hang glider or paraglider.

In case both glider and pod are falling at the same speed there is still the aerodynamic drag on the bridle which could open the pod. It's clear we are never speaking of big forces, so we need to have the pod open with a very light pull.

7) The correct staged deployment sequence is: bridle - lines - canopy. We first want to have the bridle coming out because we want the pod (still containing lines and canopy) to go away as far as possible to reduce the risks of entanglements. Then we want to have the lines, and finally the canopy must come out only when bridle and lines are stretched. This is the best way to reduce the chances of canopy malfunctions and to reduce the opening shock on the parachute. In a well designed pod, regardless of the strength of the elastics, the lines shall not come out until the bridle is stretched and the canopy shall not come out until the lines are stretched. Speaking of lines and bridle, I would like to point out that we need:

- long bridle to reduce the chances of a tangled parachute,

- long lines to get better sink-rate and stability from the same canopy

- short sum of lines plus bridle to get a faster opening time (it looks impossible at first, but there is a clever solution to this problem).

IMPORTANT: To check out the extraction, hang into your harness, put your thumb into the handle, grab it and pull it out slowly: the pod must come out effortlessly.

To check out a pod for untimely opening, while still hanging, stretch your arm sideway to check the slack in the bridle, then shake the pod without leaving the handle: the pod must not open.

To check out if a pod opens easy enough, put the pod on the floor then pull up slowly the bridle and then the lines: the pod must open easily without lifting the parachute and the canopy must get out easily. The deployment sequence, during the previous test must be: bridle - lines - canopy and must be correctly "staged" (should be the same regardless of the relative strength of the elastics used).

These simple test doesn't take more than 10 minutes (plus repack, which is always useful to get a fast opening) but could save your life: much cheaper and much more useful than a life insurance, but your partner could think different :-) :-)

While you are there, check out how old is your parachute: if it's more than 10 years old consider replacing it. An old parachute behaves exactly as a new one, of the same model, if you are going to deploy it at low airspeed. However parachute fabric is quite sensible to aging and ultraviolet rays: an old parachute cannot withstand the same high speed as a new one.

If your deployment bag doesn't work as it should, fix the problem if possible (and check it again!) or, much better, have an expert professional check and fix it (but check what the professional is doing too. It's your life which is involved!).

I practically didn't speak about the differences between envelope and diaper pods because it's not much important. What is important is that a pod works in the correct way and you can get it both with an envelope or a diaper one. Remember:

- Pods which don't stow the lines inside increase the chance of a line getting tangled.

- Old style envelope pods with the handle on the opposite side of the opening are dangerous because, in case of warn-out elastics, the canopy can easily fall out untimely (it happened to Gerard Thevenot: the pod came out of the harness but the parachute stayed inside!)

- Pods without a correctly staged opening sequence, bridle - lines - canopy, increase the risk of entanglement and malfunctioning.

Well… of course I do prefer my 5 flaps diaper pods because they fulfill all the previous requirements (as a good envelope one) but are "softer" to better adapt to the harness container, require less force to open and, when open, let immediately the canopy fully free.

If you ask a good American manufacturer I bet he would agree on everything… except the last sentence :-)

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No to stripping

Mon, Apr 21 2003, 4:00:05 pm EDT

accident|bridle|competition|Glen Volk|Kathleen Rigg|Mike Barber

Glen Volk <gvolk@voitco.com> writes:

Mike's knee (I don't publish the really deep open ones).

Given the recent accident that Kathleen Rigg had and the follow up by Mikey Barber maybe it's about time the competition committees throughout the hang gliding world outlawed stripped wires. I see no advantage in performance that makes it worthwhile to risk the loss of body parts (like part of a nose), severe slices in ones appendages (like Mikes leg) or the ever present danger of having a midair, resulting in a chute deployment only to have your "Hi Performance" stripped wires slice through your bridle (I hear that kevlar bridles are resistant to this but I don't want to find out first hand).

So how about it? Am I the only one that thinks they should be outlawed in competitions? As long as they are permitted the danger will never go away.

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BRS mounting and attachment

Sun, Apr 13 2003, 3:00:03 pm EDT

accident|battery|Brad Kushner|bridle|Dragonfly|flight park|instruction|parachute|photo|Raven Sky Sports|spin

Brad Kushner, Pres. Raven Sky Sports, Inc <Brad@hanggliding.com> www.hanggliding.com writes:

We have four Dragonflys. On our three Dragonflys with the 912-s 4-stroke motors, we have continued to mount our BRS units in the 'original' position, on the front of the root tube, over the pilot's head and forward of the wings (just like in your photo labeled, "On the Dragonflies with 583 2 stroke motors" (actually, the motor is a 582). I'd like for your readers {and the readers of the TUGS newsgroup) to be aware that it is still an option.

Of course, weight & balance is still a very important part of the decision making. If the CG is too far aft, the Dragonfly can have very undesirable spin characteristics. For this reason, we all do whatever we can to move the CG forward. I believe that the major reason that some DF owners have moved the BRS out to the front of the pilot area is to improve weight & balance.

Any weight on the Dragonfly that can be moved to the front of the pilot cage is beneficial…that's why most of us DF owners now mount the battery under the pilot's feet; every little bit helps. We suggest that, if a light pilot flies one of our Dragonflys, he should add a weight belt to the footrest. When we fly the 2-seat Dragonfly with a light pilot in the front seat and a heavy pilot in the back seat, the 'weight-belt-on-the-footrest-trick' is SOP. I believe that most of us who do dual instruction in the Dragonfly already have such a weight belt for just such an occasion.

I expect that there will be some discussion over the next few months about which position is the 'best' one to mount the BRS unit on a Dragonfly. I look forward to any new insights that this discussion will bring.

Some years ago, I was visiting at another flight park, and (of course) I was poking around in their Dragonfly to see what might be different from mine. I saw that, on their Dragonfly, the cable/bridle from the parachute was routed to a bracket/bolt attachment on the root tube (the square tube between the wings). A few inches away, the top of the pilot's seatbelt-shoulder belt was routed over the same root tube, as it should be.

However, on their Dragonfly the seatbelt-shoulder belt strap was not interlinked with the parachute bridle attachment, which troubled me. I brought it to the attention of the owner, and we discussed it, but it didn't trouble him like it troubled me, so nothing was done to change it.

My fear and concern was this: If the parachute deploys hard, and the square root tube fractures, then the parachute could become detached from the Dragonfly. With aluminum tubing, this is a very real possibility. On all of the other Dragonflys that I have inspected, the parachute bridle attachment terminates with a cable loop around the root tube, and the pilot's seatbelt-shoulder belt loop passes through the cable loop, too. With an arrangement like this, even if the square root tube fails, the parachute stays attached to the pilot's seatbelt/shoulder belt strap…far better a scenario than the other.

Please urge all ultralight owners with BRS units (or even hand-deploy parachutes) to re-evaluate the series of attachments that connect the pilot to the airplane, to the parachute, and to both. It may be that a simple thing like an extra hang-loop linking the pilot's seatbelt-shoulder belt to the parachute bridle cable may make all of the difference in the world, the next time that one of us has to deploy a BRS unit.

Here at Raven, we even have an extra bridle attachment going back to the seatbelt-shoulder belt of the rear seat, too…just in case.

It's bad enough that we learned the hard way about the pitfalls of improper re-assembly, and lost Chad; let's learn everything that we can from this tragic accident and, hopefully, prevent others in the future.

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Aeros Target 180

Thu, Mar 27 2003, 9:00:04 pm GMT

Aeros Target|aerotow|bridle|Icaro 2000|tow|Wills Wing Falcon

http://www.justfly.com/gliders/targetdata.htm

I’m sure that this is the first of a number of reports on the Target as I will have several opportunities to fly it over the next couple of months (as we race for the 100 mile flight). I had an opportunity to take an extended flight on the Target in good lift conditions on Tuesday. My previous flights had been short cross country flights to the northeast from Quest and I didn’t have time to get a feel for the glider.

Of course, as a single surface glider it is easy to set up, break down, launch and land. It is a bit difficult to aerotow, as it is a single surface glider and needs to fly near its upper speed range while on tow. Put a keel attachment to connect your tow bridle to some what in front of the cross bar to reduce base bar pressure while on tow.

I thought at first that the glider might be a bit stiff in initiating a roll, but that turned out to not be the case. I just wasn’t used to the glider. I also thought at first that it wanted to tighten up while turning.

I tested this extensively. While turning left in moderate lift, I found that I had to high side the glider a bit. While turning right in light lift, I didn’t have to do anything but let the glider fly itself in the thermal. It seems like the glider I am flying has a slight left turn.

It is not as light handling as the Icaro 2000 Relax 16 (170 sq ft), but more similar to the Wills Wing Falcon 2 170, although a little bit more of a handful because it is 8 sq feet bigger. But essentially it is very easy to turn and fly relative to the higher performance hang gliders.

Single surface gliders are so much fun to fly. They really put the pleasure back in hang gliding. Except, of course, when you try to go up wind or you want to take a long glide downwind to the next patch of lift. All those paraglider pilots put up with this limitation, so maybe you could also.

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Aerotowing single surface and intermediate gliders

Wed, Mar 26 2003, 9:00:06 pm GMT

Aeros Discus|Aeros Target|aerotow|bridle|control frame|Dragonfly|Icaro 2000 Relax 16|Rob Kells|sport|tow|towing|tug|Wills Wing|Wills Wing Falcon|Wills Wing U2

I’ve had an opportunity to at least aerotow quite a few different gliders recently so I thought I would first speak to their aerotowing characteristics.

I’ve aerotowed the Icaro 2000 Relax 16 (170 sq ft) from my shoulder bridle, the Wills Wing Falcon 2 170 from my shoulder bridle, and the Aeros Target 180 from a bridle than went to the keel and my shoulders. Single surface gliders are normally towed with the assistance of an attachment to the keel to reduce the bar pressures. According to Rob Kells you can move the keel attachment point forward until there is no bar pressure at all. Something that would be quite useful for aerotowing newer hang glider pilots on these gliders.

I have the tow point about a foot forward of the apex on the Aeros Target , just under the cross bar, and it is not far enough forward to reduce the bar pressure to a comfortable amount. I am able to tow with it in this configuration, but it would be nice to further reduce the bar pressure.

I aerotowed the Wills Wing Falcon2 170 today just from my shoulder bridle. It was quite possible to do this but the bar pressures were moderate to moderately high and I needed to make a lot of corrections early in the flight. I was not as steady on tow as I have come to expect. Not uncomfortable, and I would definitely do it again, but not perfect. I had the bar pulled into my waist.

The Icaro 2000 Relax aerotows with no problem from the shoulder bridle. It is very steady on tow. Newer pilots will probably want to use the keel tow point method also, just to reduce how much you have to pull back the bar (which is a lot), but bar pressures are minor.

In all three cases you really have to pull the bar in to get the speed up fast enough to stay with the Dragonfly. The Relax was just a lot easier to control with the bar stuffed.

All of the intermediate gliders were much easier to tow than the single surface gliders just from the shoulder bridle. Again, you overcome this using the keel attachment.

Both the Wills Wing U2 145 and 160 were a joy to tow. This is so totally unlike their predecessors the Super Sport and the Ultra Sport which required fins for aerotowing.

Both U2’s were rock steady on toe reminding me of the ATOS and other rigid wing hang gliders on tow including the Aeros Stalker. They were a pleasure to have behind the tug. I could tow with one finger on the base bar.

The bar pressures on these two gliders are very light. This made the aerotowing even easier. Rob Kells states that with about a foot of throw around trim the bar pressure is about ½ a pound on each hand and that it rises to 3 pounds per hand at the extreme end of pull in. This is nothing. But it is there and very reassuring at speed.

The Aeros Discus was also steady and very towable with one finger on the control frame. It’s bar pressures weren’t quite as light at the Wills Wing but very close. I’m going to have to aerotow it again to remember just how close it was, but as I recall it was a pleasure to tow.

The Icaro 2000 MastR 14 was also very easy to tow, but it didn’t shock me about how easy it was like the U2’s did. I think a little more bar pressure, but I’ll have to check that again. I’ve only had one flight late in the day with it.

The Wills Wing Eagle 145 was no problem towing. Very steady with slightly more bar pressure than the U2’s. I had to pull in a bit more than the higher end intermediate gliders to get the glider flying faster.

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Icaro 2000 MastR »

Mon, Mar 24 2003, 8:00:04 pm GMT

Aeros Discus|bridle|Icaro 2000 MastR|landing|Paris Williams|tow

On Saturday, I had the opportunity to take a short flight on the Icaro 2000 MastR 14, the 155 square foot, kingposted intermediate glider. Now before the topless Laminar ST, earlier versions of this glider used to be the top line glider for Icaro 2000. So it is a pretty advanced glider for your normal intermediate pilot.

I had the chance to thermal it in very light lift, and found the glider a pleasure to fly. It is not nearly as light to the touch at the Icaro 2000 Relax (single surface glider), but then it is a high end double surface glider that is a bit too big for my weight. I should be flying the MastR 13.

I found it to be about as stiff in roll as the Aeros Discus, or I could say about as light in roll. That is, it was darn easy to turn. Paris said he measured 2 second 45 to 45° roll rates on it, about ½ second faster than the Laminar MRx.

It was very easy to tow, which, of course, wasn’t true of the very early Laminar ST’s. I pulled the bar into about my chest and used the bridle off my shoulders. Landing was simple in no wind, and I had a short run out.

I think I would find the 13 more appropriately sized for me with quicker response. I’d class this is a high end intermediate glider that has predictable handling, but a bit of a lag which requires pilots to learn how to time their roll inputs. I didn’t notice it wing walking at all, so PIO shouldn’t be a problem. There is not need to go at very fast speeds anyway near the ground.

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Aeros Discus »

Thu, Mar 20 2003, 8:00:04 pm GMT

Aeros Discus|bridle|Moyes Litesport|tow|Wills Wing U2

I had an opportunity (briefly due to the lack of lift) to get a couple of flights on the Aeros Discus on Wednesday. I’d flown the Aeros Shadow previously and this is the new version of the Aeros’ intermediate curved tip glider and is meant to compete in the same market niche as that occupied by the Moyes Litesport and the Wills Wing U2. This middle or intermediate area is a bit broad from easy intermediate to high performance intermediate. All with gliders with kingposts (to keep the costs down which is another intermediate factor).

The Shadow was marketed as an easy to fly (i.e. less performance) glider. The Discus seems to be aimed at the high end part of the niche (http://www.justfly.com/gliders/shadow.htm) therefore it competes against the Litesport.

I liked flying the Discus. It was very easy to tow with the bridle just off my shoulders. There will not be any need for a fin.

It was quite easy to land in light winds. The VG was easy to pull and didn’t require any muscle tone on my part.

It seemed a little stiff in the air, but then I am really use to rigid wing hang gliders and I didn’t have enough time to fly it given the lack of lift. I had some nice long glides and they were quite pleasant, especially with the VG on.

I hope to be able to report more on the Discus later.

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Frontal instrument pod

Wed, Mar 19 2003, 9:00:04 pm GMT

Aeros Discus|Alejandro Isaza|ATOS|bridle|Flytec 4030|Garmin 12|gear|GPS|Jim Yocom|vario

http://www.geocities.com/soaringflight/frontal_pod.htm

Jim Yocom <jim@yocom-mckee.com> writes:

I have been meaning to send you my opinion of the Frontal Pod made by Alejandro Isaza, that was first mentioned in the Oz Report Ozv6n233, Friday, November 15th, 2002.

Over the years I have used several varios and various instrument enclosures. My current varios include a Ball Graphics Comp, a Digifly Gravitar, Flytec 4030 and Flytec 4030 Race. I have mounted the instruments on the downtubes, but found I prefer them on the basetube, right in front of my face. Last year I purchased Flytec's new instrument pod and flew with it and a Garmin 12 Map GPS throughout the season. As is my preference, I mounted it on my basetube.

Features of the Flytec Racing pod:

1. Enclosed windspeed turbine protects and streamlines.

2. Overall aerodynamic shape.

Shortcomings of the Flytec pod:

1. Over 20 inches long (see the ruler is 18 inches). Hard to read the GPS when thermalling and even on glide flying my Atos.

2. Long lever arm results in frequent drooping during flight.

3. Plastic case tends to warp in direct sunlight.

4. I have to disassemble the pod to connect a cable to download flights from the vario.

5. Aerotowing with this long pod on the basetube is a challenge. I modified the clamp to allow the pod to swing over my basetube, but it still was somewhat in the way of the tow bridle.

6. Price: $189 plus the 4030 case must be disassembled and vario glued to pod.

Features of the Frontal Pod :

1. 8 inches long, easy to read when on the basetube.

2. Short lever arm - no drooping.

3. Easy access to vario and GPS.

4. Nice thick plastic, no warping in the sun.

5. Price: $75.

Shortcomings of the Frontal Pod:

1. Goofy metal cover plate. I removed the plate. It is just extra weight and something else to flop around.

2. Velcro strap comes without stretchy velcro. To hold the pod securely, the strap needs stretchy velcro. I sewed this to my strap and this solved all movement issues.

3. Routing the windspeed and GPS cables was tricky. I drilled additional holes and enlarged others so the cables could be routed inside the housing. The small holes would not allow the cable ends to pass. Be very careful when enlarging the holes. Be too aggressive with a large drill bit and you can crack the plastic pod casing!

4. Overall fit & finish is not as nice as the Flytec Racing Pod. I put pinstripe tape over the crack between the top an bottom of the Frontal Pod.

I have a couple hours of flying the Frontal Pod and intend to use it at the competitions in Florida in April. I can see the instrument better and it doesn't droop. I think it is aerodynamically efficient, mainly because it is right in front of my face on the basetube. A drooping Flytec Racing Pod presents a lot of surface area!

For pilots mounting their instruments on a downtube, the long arm of the Flytec Racing Pod can be braced with a limiting string. The pod configuration may even be easier to read than the Frontal Pod on a downtube.

For me, mounting the Frontal Pod on the basetube is the preferable setup. Of course I will have my Flytec Racing Pod with me in Florida as a backup just in case ; )

(editor’s note: I flew for the first time with the pod today. I love it because it puts the instruments right next to me where I can see and hear them. I was flying a Target and a Discus and the instruments were out in front of me, so I wasn’t disturbing the air flow around the turbine. I don’t know what I will think when I try them on an ATOS. Jim has an ATOS.

I used the standard Velcro that came with the pod. It held fine for me on the round base tube, but I wasn’t hitting any lift or turbulence (well, the tows were pretty exciting). On the Target I had glued a piece of inner tube a few hours previously with Shoe Goop to the round base tube. This provides extra friction and I think that this is a good idea.

On the Aeros Discus (liked the glider, btw) I attached to the bare round base tube. It flipped down once, but really, it held pretty darn good.

Like Jim I cut off the extraneous metal cover.

I didn’t enlarge the holes, and all the cables and ends fit through them with a little work. I glued the pieces of Velcro to the pod, but one came off tonight when I took the Brauninger IQ/Comp vario out. Looks like I’ll need something other than household cement for that.

I had to add a piece of Velcro to the turbine to get it to fit snuggly in the hole provided. It was difficult to get the main Velcro through the hole in the pod, and I needed needle nose pliers to do it. More instructions would have helped.

I have no idea how aerodynamic it is, but I like the instruments being close enough that I can actually read them and easily punch the buttons.)

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Wing walking

Mon, Nov 25 2002, 6:00:01 pm GMT

aerotow|bridle|control frame|Mark "Forger" Stucky|tow

Mark Stucky <stucky_mark@hotmail.com> writes:

I have found that the wing walking that occurs in free flight (off tow) is usually due to a pilot not being in tune with the wing and not having the correct timing of his control lateral responses to the glider's yaw/roll response. Some gliders will tend to do an unstable yaw/roll response which some pilots (and manufacturers) will call PIO. I can't speak for all gliders but these oscillations are often not due to a PIO because they would occur at the same airspeed and angle-of-attack if the pilot was replaced with a fixed weight. A pilot may learn to stabilize these unstable oscillations, but if they can't it doesn't make it a PIO.

The problem is pilots tend to correct for the glider's roll motion because that is what they can readily observe but to stop wing walking you need to stop the small yaw motion that occurs prior to the roll. Observing a yaw is difficult on a hang glider because of the lack of a fuselage extending forward in your field of view and especially because a yaw tends to twist your body slightly making it impossible to keep a constant sight reference.

I found a useful technique to counter wing walking off tow is to spread my hands farther apart on the base tube and use stiff arms. By keeping my upper body square and my arms stiff I can feel the increased pressure in one hand (caused by the start of a yaw prior to the bank occurring). I apply pressure on that hand and stop applying it as the pressure reduces. This works well for me to automatically correct for the small oscillating yaw pressures.

Visualize the nose of the glider starting a small yaw to the right. If you use my technique you will feel an increase in pressure in your left hand and countering it with additional pressure will correct the yaw.

Unfortunately, this procedure doesn't work well on an aerotow (it took me embarrassing myself at Wallaby after a couple of years of very occasional hang gliding to make me think about why).

For our purposes let's assume we are towing a high performance flex wing with the towline only attached to the pilot's shoulders. The reason it doesn't work well is when you apply more pressure to the base tube with an arm then the tow force is also being differentially applied with respect to the centerline of the glider.

It's easy to visualize if you imagine you are holding the base tube with stiff arms spread so far that you are holding each corner of the control bar. Now you are effectively towing the glider by a three legged "Y" bridle with two of the legs made up by your arms and the third leg your hang strap. Now imagine the glider's nose starting an unwelcome right movement. In this extreme example we will keep our upper body and left arm rigid to counter the pressure. Unfortunately, by doing so we have just effectively "fastened" the tow force to the left corner of the control bar. Anyone can visualize that towing a hang glider by the left corner of the control bar will cause a more severe right nose movement.

You can make a similar mistake by moving your upper body laterally to correct for a turn. Your weight shift to correct for a high wing could also attach the tow force to the high side, interfering with your weight shift correction.

To do a smooth aerotow you need to be able to make small lateral corrections with your lower body while keeping the tow force centered within the control frame.

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Retractable bridle »

Tue, Nov 19 2002, 7:00:02 pm GMT

bridle|Peter Kestel|release

Peter Kestel <peter_kestel@webone.com.au> writes:

This design has been tested in the field & works very well. It is the latest evolution of a design that has seen the input from many pilots. It is a 1:1 system that uses a front cord release. Variations of the design allow for 2:1, however the release cord must then be tied onto the base bar, & pulled in separately. This is because the release cord must end up being the same length as the bridle if they are both to be pulled in together. I am only too happy to answer any queries.

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Retractable bridle »

Mon, Nov 18 2002, 7:00:04 pm GMT

bridle|Peter Birren

Peter Birren <peterb@ameritech.net> writes:

The retractable bridle for static towing has been in use by several of the
Reel HG Pilots in the Chicago area for well over 10 years. A large dog leash
reel is attached to the keel forward of the crossbar. It is usually re-wound
with spectra line which is guided through a rapid link at the back of the
sail's lower surface. No pulleys are involved. The rapid link on the end of
the bridle prevents the line from rolling fully into the reel.

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Retractable bridle »

Sat, Nov 16 2002, 6:00:02 pm GMT

bridle

The clever folks in New Castle have come up with a retractable bridle that works off some pulleys and bungees up in the sail. The line runs through a pulley on the bottom of your keel just in front of your hang point.

After you release from the tow line you undo a snap shackle that connects to your waist line and the bridle line retracts into your sail. I’ll have pictures soon that will give you a better idea of how it works.

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Peter Birren on weaklinks and tow bridles

Mon, Oct 4 1999, 10:00:09 pm GMT

bridle|Jeff Nielsen|Linknife|Peter Birren|Scot Huber|weak link

Whenever I write about weaklinks (https://OzReport.com/Ozv3n118.htm), I seem to get quite a reaction. Everyone seems to think that God herself gave them the directions for doing weaklinks. Maybe they are right, but at least they are deeply felt.

Peter Birren (<peterb@ameritech.net>), has his way of doing both weaklinks and bridles and he sure doesn't feel comfortable about the way other folks are doing it. Here's what he had to say:

I think I've told you some time in the past that the Reel Pilots also use 130# links. We get ours from Catch the Wind Kites… it's braided Dacron kite string, and very consistent.

Their toll-free # is: 1-800/227-7878

They also have 150# line that we use for static towing the beefier pilots.

Their line is available in 300' and 1000' rolls. Last year a 300' roll cost $7.99 + shipping; a 1000' roll cost $15.99 + $4.00 S&h. When we (I) cut the whole roll into 18" sections, the cost per weaklink is $.03 each.

Tied with a double fisherman knot, a single loop (2-strand) breaks around 120# and a double loop (4-strand) breaks consistently at 230-235#. I use a 4-strand for aerotowing and place it at the apex of the bridle v/s at the keel and have not had a failure yet. When aerotowing, at Leland IL, I fly behind a Kolb MkIII with a 912.

To be clear here, Peter is putting his weak link at the apex of the V-bridle and attaching it to the towline. At Wallaby Ranch for example, the weaklink is placed most often at the conjunction of the V-bridle and the release at the keel. This location places half the forces on the weak link that Peter's placement does.

Even when pilots tow only off their shoulders (no V-bridle), I have most often seen them use only one loop (not two like Peter).

When I asked Peter about his, he responded:

Prologue: a while ago I led a rail against the present state of release setups for aerotow. As I see it, and from what I read, there's a good potential of an unthreading bridle/weaklink to hang up in the ring on the tug towline.

By threaded bridle, Peter means a bridle line that goes through the ring at the end of the tow rope. Peter puts his release and weaklink at this ring and does not thread his bridle through it.

Peter continues:

Don Hewett and I share the opinion that the "threaded bridle" concept should never be used for that and other reasons. We have outlawed its use for static towing here, and I find it ludicrous that it should be the release procedure of choice for aerotowing today.

I see it being used for 2 main reasons: (1) there's a book, "Towing Aloft" that promotes the concept that (paraphrased) all good tow bridles should have a backup release. So the (Quest/Wallaby) systems have a designed-in hang-up problem so that a backup release can be utilized. (2) convenience; that the pilot can stow a bridle easily and get it out of the airstream.

(Side note: One of the authors does not use a weaklink for his normal static towing, doesn't require that pilots on his system have parachutes, and does not require radios on the gliders… no-brainer basics IMO)

The Plot: with a standard threaded aero bridle, with a weaklink placed at the keel, a single loop is required as minimum as it takes only half the load. In an Apex Release System (ARS), as Hewett and I promote, the release and weaklink are placed between the bridle and towline (ala static line/Hewett Cm bridle), so the weaklink takes the full brunt of the tow force. Therefore, it has to be twice the strength of one mounted at the keel… hence the 4-strand, or double loop weaklink. This is simply a single loop placed through the towline ring, then taking the loop ends and attaching them to the release (or passing both loop ends through the Linknife for cutting).

These others aren't "underdoing it" but are using the appropriate strength for the placement on the bridle. At the Apex, a full-strength weaklink is needed, and therefore the 4-strand. My 4-strand has a working load of ~230#, twice what is needed at the keel.

The release line for an ARS can be attached to the harness, or to the pilot's wrist, for easy handling.

The Plot Thickens: With the ARS (and 4-strand weaklink) no backup is needed save for a hook knife. No brake cable and complicated routing of release lines to the keel are needed. And furthermore, as has been related to me by several pilots who have fallen into the "comfort of what I have done in the past" trap have told me, they want to have a release that can be activated without removing a hand from the base tube. This IMO gives them a false sense of security.

This is much different than Wallaby Ranch or Quest Air. I think they're doing the "backup" setup as a CYA arrangement. You know, if they didn't provide a backup system and someone has a brain lock…

My ultimate solution (oooo, that sounds ominous!) is pilot training. Practice with committing to release and recognizing the timing needed is paramount. By using the threaded system, Q, W, and A are lulling their students into that false sense of security and promoting some bad habits that extend and continue to advancing and advanced pilots.

Epilogue: The ARS is simple. It's lack of complexity mean it's easier to set up. It's the same release format, relatively speaking, as static line and payout. (I know pilots who won't static tow because the release doesn't have a backup… they can't make the mental transition and our club is suffering for it.)

I firmly believe that IF an aero bridle is to be threaded, that the primary release should be at the keel, secondary at the pilot. This way the pilot is not left, for however brief a period of time, with a squirrely glider due to the pull on the keel should the bridle hang up.

I have an opinion (on many things :-) and voice it often. Few agree, most are rankled that I speak my mind, others just go about their business knowing in their minds that they are right, no matter what.

On another, similar topic, most of the hard core static pilots here don't like aerotowing. More correctly, they prefer static over aero because static is a lot less work, less costly, more team oriented (every launch is a party!) v/s the solo-ness of aero. The guys I know who say they prefer aero are usually heavier pilots (like Dr Jeff Nielsen and Scot Maue) who don't get to release as high as most others, those who live close to an aeropark, and those pilots who were weaned on aero. It's the last group I'm working on to start static towing, but so far am having little success with. Oh well.

A few pilots have gravitated to static, and they're doing well. As well, there are only 3 other aero pilots here who use the Apex Release System (with Linknife).

When I asked Peter about the extra line of a Hewett bridle, he responded:

Some static pilots here in the Chicago area have taken to using large dog leash reels. They mount the reels on the keel, forward of the crossbar and attached to the nose. Then having replaced the line in the reel with spectraline, the line is routed through a ring of sorts at the downtube apex. Upon releasing from tow, the bridle gets automatically pulled back up in the sail.

One pilot neglected to route the line through the aforementioned ring, launched, and the bridle ripped about 4 feet of his lower surface. Oops. The tow continued for a little bit as normal and he said he didn't feel anything different, but got worried about the sound (ripping material) so he released and had an uneventful landing.

The bridle reel does work and I've recently installed one in my HP-AT. It does completely away with the mess after release. I also use a much smaller leash reel for my release line. Only caveat with this is to make damned sure to have it locked before launching (you would not have wanted to be there the one time I _really_ needed to release and only pulled out more line).

I typically use 3000 feet of towline and have released at well over 2900 feet on numerous occasions. The upper line does present an interference, but I've learned to live with it. It's not really that bad… actually, it's a good directional indicator when towing through, uhhh, thicker atmosphere.

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