RivetBangers.com

I know most of you check out the other forum, but I think this is important enough to repost here for those who don't. There was recently a RV-7A which suffered what is to believed a break-up in flight. I am not going to speculate on exactly what happened, but from the few pictures I've seen, there might of been a failure in the empennage.

I am not going to preach what everything should check on their particular RV, but this is my personal check list the next time I go to the hangar:

1) Check for cracks on the rod-end bearing attachment points for the elevators and rudder
2) Check the lock-nuts on the rod-end bearings are secured tightly against the spar.
3) Check the trim tab and all securing hardware (Servo motor or trim table cable)
4) Check for any asymmetrical loading between the elevator and horizontal stabilizer.
5) Check for asymmetrical loading between the rudder and vertical stabilizer.
6) Check for play between the elevators
7) Check Horizontal Stabilizer attachment to fuselage (Cracks and attachment hardware).
8 ) Check Vertical Stabilizer attachment to fuselage (Cracks and attachment hardware).

Can anyone else think of other items to check???

This is a pic of a crack one person noticed on their RV's elevator spar:

Mike, it was with great sadness that I learned about the accident you're referring to. And I didn't even know him. But recently I learned of a new product made by Anti-Splat-Aero. These are the same people who make the "Nose Job" stiffener for the "A" model RV's, and a number of other great products. I plan on installing the Nose Job on my 7A. I've also had the nose wheel bearing mod for my front wheel done by them, and I'm very pleased with it. Totally sold on this mod. Anyway, the new product is a set of stiffeners for the vertical stabilizer attachment. I've seen a few reports surfacing of cracks developing where the VS attaches to the HS. This new set of stiffeners can be retro-fitted to any RV-7 or 9 in less than an hour, and I'm sold. I'm getting them and installing them. Like you, I don't want to speculate on what happened at the recent accident until we hear the results, but this is peace of mind and cheap insurance as far as I'm concerned.

I met Allan Nimmo personally at Vans Homecoming this summer and had quite a nice talk with him. He flew his beautiful RV-9A up from California so we could see it firsthand. If you have seen his products and postings on the other forum, you know he has been met by a few with some strong outbursts and vocal emotions. But I found him to be very personable, a great guy. He has spent a lot of money developing and testing his stuff before putting it out there for us. I liked him. Just my opinion. Take a look for yourself at these new stiffeners, here:

http://www.antisplataero.com/Vertical_S ... r_Mod.html

There is also a very good video discussion, demo, and installation that can be seen on YouTube here. It's also on his website, but this link takes you directly to it:

http://www.youtube.com/watch?v=xH0iN1lMj5k

In this video, he discusses the issue of cracks in this part, and even shows some photos. Worth watching!

I certainly don't want to downplay Anti Splat Aero, Alan certainly has come up with some great products and he's done some great analysis of A-model nose gear problems.

Even though I'm not a mechanical engineer, I picked up enough about structures from past work in the certified airplane world to make me cautious about making changes to primary structure. I know there have been some cases of cracking in that vertical stab splice plate. Making that area more stiff - and theoretically less prone to fatigue cracks - could move stress concentrations to another point in the structure that could in turn fatigue and crack. You really can't know for sure which outcome will be the case without some analysis.

I'm not at all trying to be a nay-sayer. Just use extreme caution when considering reinforcing key parts of your airplane's structure...the law of unintended consequences may apply in full force.

My $0.02...

Dave

I have never been comfortable with fiber lock nuts on connections like the elevator pushrod to control horn. I have been told by very experienced people on the other forum that this style nut is completely adequate and more or less, I'm in left field. That said, the current tail group inspections have revealed more than one fiber lock nut loose on the pushrod bolt. If the fiber lock nut is completely adequate, why the loose nuts? I will be using steel lock nuts at a minimum.

Robert

all the nylok nuts were tight...but I did find one rod-end jam nut loose.