2005 Masters maneuver #4 - Warning

[Grow Pattern]

This is a sort of public service announcement, or at least please regard it as a "Heads-up".

For all of you who are flying or will be flying the Reverse Avalanche you might want to check your wing tubes and phenolic tube wing supports.

It seems that if you go into the snap a bit hard you can bend your wing tube or, in the worst case scenario break, your wing. The plane is pulling some G's at the bottom of the loop and then you add more by putting in a lot of elevator to get a good break for the snap.

Last year I had several incidents reported to me and my initial reaction was to say that they were probably not flying the maneuver correctly. "You need to slow the plane down at the bottom of the loop", I said. I must add that what I said did not impress an FAI and pilot and District masters champion very much. :-(

So strapping on my asbestos underwear I decided to do some testing of my own. At the end of November 2004 it was nice here in NJ. I took the Focus-2 and the Temptation out for a day of Masters 2005. Both planes were inspected for tube tightness and the wing covering touched up with the glove-iron.

Twelve flights later and an average of 10 reverse avalanches in each flight I went home thinking all was well. (It got cold and a bit dark too).

Back in the shop the first thing that I noticed was new wrinkles in the covering on the Temptation wings. Nothing was loose. To test this I put the wing-tube in the wing and leaned on it a little. All was well but I was beginning to think that the wing must have flexed to cause the covering to loosen up. A bit like what the covering sometimes does around the aileron horns. It this case it was at the  roots above the tubes - both sides.

Then I turned to the Focus-2 wings. Not good! The wing-tube could now be moved up and down and I could hear foamy crunches in both of the wings. Both wings have Carbon tube wing tubes and it dawned on me that they could not bend (much) or stay bent. That is why I had not seen this before. The forces were applying themselves to the ends of the wing tubes. I opened up both panels and added epoxy and micro balloons to stabilize the sub ribs. It was an easy repair but could have been a lot worse if I was not looking for it.

I am advised that stress damage is cumulative and that it does not show up initially. It certainly had not revealed itself while I had been demonstrating the 2005 schedule over the late summer of 2004. So where does this leave me?  I think we have a potential problem that requires frequent preventative equipment inspection depending upon the planes that you fly. If you can slow down your plane and it is at around 10 lb you may never see this happening.

I would strongly advise checking your wing with the wing tube in place to look for tube movement. Also look for straightness if you have an ali-wing-tube.

This situation is a bit unique for me. It is the first time I have been involved with a maneuver that you don't know you are doing it wrong unless you fly it that way too many times. And then only if the wing shows damage or even worse it breaks in the air.

Regards,

Eric Henderson.

P.S. The only time I remember seeing a reverse avalanche before is in the hardly flown? current FAI Finals schedule.
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