Paramotor Safety

Pylon Racing Accident Analysis

2012-05-13 Michael Mixer's Recon Collapse | Related article: Reflex Wings & Owners Manuals

 

This one was a surprise to us. Conditions were good, the pilot competent, and his flying wasn't overly aggressive.

During the second run of the 2012 U.S. Pylon qualifier, Michael Mixer was making good time and looking smooth. He had been practicing and it showed. I was recording and was impressed at how far his skills had come and how relaxed he seemed to be on the course. It may not seem like hanging on full speedbar is particularly challenging but doing so smoothly, while making turns, coming on and off speedbar at the right time, can be more difficult than you think. He was smooth, fast, and making good race lines.

Setup

First a few notes.

1) The Velocity Recon is a reflex wing where the tip steering pulls approximately the outboard 20% of the trailing edge. That's more than most reflex wings. There are also stabilo steering toggles which are intended to be used on full speedbar but tare not very effective, so competition pilots frequently push it by using tip steering that activates the outboard brakes, in spite of increased risk. This wing is essentially a prototype and, as such, remains up to the pilot to explore its envelope.

2) The wing has little history of competition so its behavior in this condition is not well understood. As of this writing I have seen no pilot manual and doubt one was available at the time this occurred. But even if there was one it doesn't mean this subject would be covered. In a user manual for the Ozone Viper 18 it is not mentioned because they only sell that wing to competition pilots who know the risks and are on their own to explore its limits. That is, I suspect, the situation with the Recon.

3) Video by Rick Hunts (below) shows that Mike is, in fact, using the tip toggles which backs up what the pilot says (not using main brakes).

4) There was sand in the trailing edge, probably about 3 pounds per side give or take a pound. You can see it in the video and witnesses reported it while he was flying. Also, some witnesses reported some "flapping" of the trailing edge although I could not tell anything more than normal brake input and his hands are moving in small, frequent amounts. It is, however, not uncommon to get some flapping when there is sand in a wing and the witnesses were in a better position to tell.

The accident

On full speedbar, trimmed full fast, it came out of the blue. Just as he started the second big turnaround, 25 feet high, a burble, possibly from the pylon, pushed a little piece of the left wing down, breaking through the minimal lift opposing it and started a cascade of actions that, once begun, left no chance for recovery. As that little section folded down the fast-moving slipstream pushed it down and back, pulling more fabric with it until the entire left side was completely folded down and back. It looked like the left side just "let loose".

Inertia did the rest, flinging him forward, up and left. He let off the speedbar and power immediately, within a few tenths of a second, but he was now along for the ride. I watched it step by step as did a number of others (some will be on YouTube, mine will be in video 3, if not sooner). You can clearly see the trailing edge deflected consistent with main brake application prior to the deflation.

The wing reinflated when he was pointed straight down, about 25 feet high, and swinging counter-clockwise. He impacted mostly face down but on his right side then bounced and landed on his back. The bent-up cage is testament to the paramotor having absorbed a lot of impact.

Probable Cause

The most direct cause appears to be a combination of trailing edge deflection and the rollout that was occurring which would have redirected the airflow slightly downward, was enough to start a front tuck of the left 1/3 of the wing. Being at full speed meant that, once the tuck started, fast moving slipstream air pulled much more of the wing down and led to the dramatic result. Contributing factors may have been: 1) Tip Steering system that applies brakes over a relatively wide range of trailing edge, 2) Sand in the wing, 3) Rotor from the pylon.

Regarding the wing's tip steering affecting more of the trailing edge. I can attest to this because, during my review, I noticed that I was able to control pitch with the tip steering. That's quite handy, actually, unless it destabilizes the outer part of the reflex airfoil. Testing would be in order and, if I get a chance to fly the 22 again, I will do the testing up high.

Recommendations

1. Don't fly the Velocity Recon on full speedbar using any brake input including the tip steering. It may work for some time but you are, in fact, far closer to a potentially catastrophic collapse. Use only the stabilo toggles (see diagram above right) when on full speedbar. There are quite possibly other reflex wings with this same behavior but they have not been pushed as hard. Stabilo steering has never, to my knowledge, caused this to happen so it should be reasonably reliable. If you do test your wing (whether the Recon or other glider) be prepared to do your test up high.

I flew this wing just like Mike did, using the tip steering, when I reviewed it and was under the impression this would be OK. Obviously it is not. Like the Hadron, when on fully speedbar and trimmed fast, steering is only to be done through the Stabilo togles.

2. If you have sand in your trailing edge, avoid flying trimmed fast and never use the speedbar. Look at the trailing edge, if it's deflected, you have enough sand to worry about.

About sand in the wing: Here is an article with video from the German Certification organization DHV about sand in the wing. Here is the Accident Report. In the case of this accident, approximately 3 pounds of sand in one stabilizer was found to make a tip collapse and cravat more likely. Although this strongly suggests that sand in the wing is more dangerous than most thought, these two accidents are essentially unrelated. Michael's wing did not cravat and, in fact, recovered almost right away. But the sand could have been a factor because it would pull own on the very trailing edge just like the brakes would do.

3. Realize that, whatever wing you're flying, just because it hasn't collapsed on full speedbar doesn't mean it's not about to. Michael had practiced a fair amount and had never had anything like this. He was, essentially, doing everything right and still this happened.

4. Consider reducing the amount of inboard tip steering line connections.

Aftermath

Michael hit in the sand going probably 25 mph. Had he hit one of the many solid objects nearby it would have likely been fatal. Had he not been in such great shape it might not have gone so well, either. We are lucky to still have him. Hopefully he will come back to continue his contribution to the sport, it would be sorely missed. Whether he competes or not is something that will no doubt be a big topic of debate with him and his wife! If he does compete again, look out. I'll bet there will be no sand in *his* wing.

 

 

If you fly on speedbar while trimmed fast, do NOT use the main brakes! Don't use any brakes that engage the trailing edge, even if just the outer 15%. Or if you do, experiment up high and by flying through your wake. You may do it successfully a 100 times but, in reality, be very close to a catastrophe.

Read the manual, if available, to learn about any dark corners. But realize that, on uncertified wings, those corners may not yet be fully explored.

A note for free flyers. I'm told by an experienced free flyer that, in the past few years, they realize that the same phenomena is true on their (non-reflex) wings--brake use on full speedbar makes a collapse more likely .


© 2016 Jeff Goin & Tim Kaiser   Remember: If there's air there, it should be flown in!