Oz Report

Tin Cup

(This topic is in: <-- Apr.23 Apr.22 Apr.21 Apr.18 Apr.17 Apr.16 Apr.15 --> )

Evidence based procedures (Francisco Grande, Casa Grande, Arizona)

Light non locking aluminum carabineers are used almost universally for aerotowing operations.  There are good reasons for that and their use has evolved over time as the risks have been measured by experience.  We go back and look at the risks and the mandates from the HGFA.

The HGFA is about to make some changes.  Let's examine those changes and see if they are justified and whether they should be adopted more widely.

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Discuss Tin Cup at the Oz Report forum   link»

Davis ranked US #1 flex wing pilot

As the Santa Cruz Flats Race approaches (Francisco Grande, Casa Grande, Arizona)

The latest NTSS class 1 ranking:

1	STRAUB, DAVIS	1234
2	SHAPIRO, JEFF	1015
3	SMITH, CHRIS	971
4	O'BRIEN, JEFF	951
5	WILLIAMS, MICHAEL	766
6	MARTIN, DUSTIN	716
7	WILLIAMS, PARIS	691
8	CARTER, KEVIN	681
9	SIMMONS, JACK	659
10	MAJORS, ZAC	658

The NTSS ranking was prepared by Chris Smith from a template worksheet developed by Paul Klemond.

And Jonny is ranked number 1 in the World: http://civlrankings.fai.org/?a=326&ladder_id=1

Discuss Davis at the Oz Report forum   link»

Thinking about reactions to an accident

So what was the cause and what are the solutions? (Hughenden airport, QLD, Australia)

The coroner's report from February 27th, 2008 is found here.

The HGFA accident report from April, 2007 is found here.

The pilot was engaged in "static line towing." That is a fixed length of poly line (usually 2000') is connected (with a weaklink) to a cylinder (usually a brake cylinder) connected to the back of a car, usually the bumper or a two hitch.  The brake cylinder is normally connected by a hydraulic nose to a dial which displays the pressure and is viewed by the car or truck driver.  There are numerous descriptions of this common (in Australia) type of towing in the Oz Report.

The pilot was flying with a retractable bridle.  It was perhaps like this one: http://ozreport.com/6.238#2 or this one: http://ozreport.com/6.237#1 but maybe it is slightly different (see the description given in the reports).

The tow rope stayed connected to the "pilot" after he "released" and after it was released from the tow vehicle (as was normal at the end of the tow).  The rope tangled into foliage/trees by the runway and that led to the accident and fatality.

 Chris Fogg, the general manager of the HGFA, looked into the accident (along with others) and found that the "snap link" at the end of the tow line caught the bridle.  The an end of the "snap link" caught in the braiding of the bridle (a water ski rope) which was made of a loose weave.  Chris also notes that the pilot didn't have a hook knife accessible to cut the bridle line and free himself from the tow line.

Based on this report from Chris the coroner recommends:

1.  That the HGFA Tow Manual be amended to recommend that screw gate type rings, NOT snap links be used as the connection ring between the towline and the pilot to minimise the risk of the bridle or any other part of the craft being snagged after release.  The potential for the clipping ability of the snap link will be eliminated by this means, and thus the risk of the pilot and craft remaining attached to the tow line after intended release.

2.  That all clubs make it mandatory that a knife be carried in an accessible position while in flight.  (It is noted that the HGFA Tow Manual and formal pilot training procedures already strongly recommend this and that the pilot examination for achieving the tow endorsement includes a requirement that this knowledge be held.)

It is my understanding, but I have yet to receive the documents, that the HGFA has mandated or will soon mandate the use of ring/screw gate termination on tow ropes.  I will provide those references/documents when they become available.

This is the beginning of a discussion of whether these measures are appropriate and justified by this accident or for other reasons.  I expect to ask numerous "experts" about their thinking about this issue.

First, a few questions.  What exactly is a "snap link?" What is the kind of "snap link" used in this accident?  What material was it made of?  What condition was it in?  How heavy was it?  What is the shape of its "hook?" Can we know exactly which "snap link" was used?  Please provide a URL/link to such a "snap link."

How does a "snap link" compare to the light aluminum non locking carabineers used in the US and often in Australia?  Here is one example and here is a lighter example.

Is this or this the type of screw gate type rings that is being recommended, or does Chris have specific ones in mind and can he say exactly which ones they are?
 
How exactly did the bridle connect with the "snap link?" It would appear from the bridle line did not go through the "snap link," but rather that there was a weak link connecting the end of the bridle (a three ring circle perhaps) to the "snap link." Is this true?  If this is the cause, what caused the bridle to become entangled with the "snap link?"

Was a polypropylene rope used for the static line tow, as is the usual standard?  This rope is relatively elastic.  Did the elasticity of the tow rope play a part, or a big part in this accident?  Is this being overlooked in the accident report?

What is "...single standard chain link used as the weak link tow ring?"

What about the "loose weave" of the bridle?  Is it the case that that was equally at fault for this accident?  Why is there no recommendation re "loose weave" bridles?  Wouldn't it be the case if the bridle was a tight weave that this accident wouldn't have happened?

The HGFA accident report discounts this but does not give an adequate explanation as to why it is discounted.

This was a "static line" towing accident.  Do the circumstances of this accident apply equally, less so or more so to aerotowing?  If so, why?  Do the type of tow rope, the angle of the tow, the type of bridle used have important implications as to the safety of the towing procedures?

Light aluminum non locking carabineers are standard in US and most Australian aerotow operations.  They have been used successfully on many thousands of aerotows.  Do we have any incident reports and/or any statistics which show them failing?  Any cases where the aerotow pilot failed to release?  Any cases where the bridle wrapped around the carabineer?  Where the carabineer snapped onto the front wires?

How dangerous exactly are these devices?  Do we have a way of quantifying it?

Do we have reports of incidents of "heavier" rings or locking carabineers hitting pilot's in the face and causing injury?

That is, do we have an evidence based way of evaluating the level of risk that light aluminum non locking carabineers present, if any?

It is my experience that very few if any pilots wear hook knifes, or wear them in places that make it easy to get to their bridles to cut them.  What is the percentage of pilots who do this?

Isn't there a much easier way for the pilot to release from an aerotow bridle?  Isn't there a fundamental difference between a small thin Vectran or Spectra pro-tow aerotow bridle and the type of bridle that was an important part of this accident?

I will be taking a position in this discussion, based on my experience and on those of meet organizers and pilots I speak to, but I am very open to new evidence and I am very open to presenting opposing positions.  In fact this whole discussion started because of concerns raised by another pilot.  I'll be presenting his point of view (and maybe he will also) as well as the opinions of others regarding this issue.

The HGFA is about (or has) taken some actions based on this accident report.  Is the report valid or does it not take into account the vast experience of the professional aerotowing operations?

I've got real (not rhetorical) questions.  Do you have the answers?

As a matter of record, as the meet director at the 2007 Worlds I required pilots to use a system that may not match the requirements of the current HGFA manual and used light aluminum non locking carabineers.  It is a system that I and many others have used as participants in many Australian aerotow competitions (including the Worlds in Hay) and in many US based competitions.  I therefore have a dog in this fight.

I also sell barrel release and tow bridle components that may not match the HGFA requirements as per their 1999 Tow manual (we'll get into that later), but are not an issue here.  I believe these components to be completely safe.

Discuss Accident at the Oz Report forum   link»

A few answers to the questions above

I am trying to get the answers to my questions above, so please help. (Hughenden airport, QLD, Australia)

I sent out requests for answers to various knowledgeable individuals in advance of publishing the article above.  These are the answers I have so far:

Other questions to ask are regarding:

the mass of the rope / fittings
stiffness of the rope
aerodynamic fairings on ropes (covers over the carabineers)

These factors may play a part in knotting.  Knotting may be something that is important such as the Tocumwal fatality with knotted rope around a side wire, or knotting of a rope through barrel release (many of the systems have evolved with this in mind, the Dragonfly pilots have this release on the tug end and have the longest of bridles, they are very particular about the rope that they use in this area).  Also, look at aerodynamic fairings on ropes (covers over the carabineers), when employed correctly may play a role in reducing the risk of capturing a wire.

More on the Tocumwal aerotow accident in a later article.

Snap link: http://ronstan.thomasnet.com/item/stainless-steel-hardware/stainless-steel-carbine-hooks/rf652?&seo=110

Ronstan RF652 hook is typical and has previously been used in Australian competitions, only with long leaders (in front of the release) to mitigate risk of the hook catching a part of the bridle or glider wires.

How do these stainless steel hooks compare with the light weight non locking aluminum carabineers?  At 2.4 oz.  they are 0.7 ounces heavier than the light weight carabineers linked to above, or 40% heavier.

What is "...single standard chain link used as the weak link tow ring?" You take a chain and cut every second link, leaving you with (usually some rough welded edged) rings.

The bridle was a non recommended type, non conforming because it is not the mandated non stretch type (such as spectra/dyneema).

Actually this is what the HGFA tow manual says:

"3.  3.1 - Bridle Construction

Bridles should be constructed from pre-stretched rope.  This is necessary to avoid injury to the pilot in the event of a weak link break or release under tension.  A bridle that can stretch under tow will spring back toward the pilot if the load is suddenly released."

"Do we have reports of incidents of "heavier" rings or locking carabineers hitting pilot's in the face and causing injury?"

This is a very real risk and there was an instance of injury in Deniliquin by a rope type bridle.  This risk is mitigated in Australia by mandated low stretch bridles and low mass releases.  Horse panic type releases such as illustrated in the Canadian tow manual are not recommended.  Safety glasses are recommended.  Vecrtan / spectra barrel type releases are fine in this regard.

"It is my experience that very few if any pilots wear hook knifes, or wear them in places that make it easy to get to their bridles to cut them.  What is the percentage of pilots who do this?"

I know of one person only who does not wear a hook knife.

That would be me?  :-)

Discuss Answers at the Oz Report forum   link»

Software for flying geeks

Lots of little pieces of stuff

http://www.cumulus-soaring.com/soaring_links/software.htm

Discuss Software at the Oz Report forum   link»

Turning the sky into a commercial

Company makes floating ad 'clouds' in the shape of, well, anything

http://www.msnbc.msn.com/id/24162063/

An artificial foam cloud in the form of a peace sign floats in the sky.  The formations, created by Flogo, are made of a soap-based foam laced with lighter-than-air gases.

The company uses re-purposed artificial snow machines to generate the floating ads and messages, dubbed Flogos.  The machines can pop one Flogo out every 15 seconds, flooding the air with foamy peace signs or whatever shape a client desires.  Renting the machine for a day starts out at a cost of about $2,500.

Discuss Commercial at the Oz Report forum   link»

Party time in Arizona

We'll all get together at the Francisco Grande (Francisco Grande, Casa Grande, Arizona)

The Santa Cruz Flats Race apparently is an excuse for a party.  We're heading out this morning from near Palm Springs and should get there around 5 PM.

David Glover should be there soon.  Steve Kroop from Flytec is coming for the weekend.  Rob Kells and Trish are on their way this morning and will be there this evening.  Over sixty pilots are coming.  Jonny Durand, who has seemed very sober over the last few months, is looking forward to the Margaritas, that pilots are served before they get out of their harnesses at the Francisco Grande.

I'll be reporting on the competition, starting soon.

Discuss Party at the Oz Report forum   link»