RV-7/7A In-Flight Breakup Accident Information

[jask]

I an 77 now and have owned a 7A Kit for several years. I haven't done much on it for the past 4 years since being treated for cancer. Soon after my initial purchase, I put an 8 rudder on my kit. I had read all accident reports because it is a good method of learning. The 9 rudder was installed for better spin recovery but since I do not intend to do any intentional spins, that didn't bother me. If I spin unintentionally, it would be at pattern altitude and I would probably die regardless of the rudder installed.

The cancer treatment was not kind to me and a few years ago I went looking to buy a 6A. My wife is a really good pilot and I just fly the right seat now. We both love the 6A and have finally got the Dynon for a panel upgrade. We sure enjoy the airplane and I still work slowly on my kit. I was at Anti Splat recently getting the bearing upgrade. He has some fixes for the 7/9 to strengthen the forward vertical spar attach point. He feels that is the failure point in a rudder event. BTW, I have toyed with being a novice machinist for the past 20 years and Allan is really good. He also gave me some #9 lead shot to put in my steps.

[grubbat]

In my humble opinion, having to use TAS when flying a RV coupled with a narrow margin rudder is a recipe for more inflight failures in future. Data is not emotional and it’s going to happen. That’s just the way it is. Education to individuals may slow the occurrences but relying on human memory is just not good mistake proofing. How far does one go? Well, if a rudder change will bring the inflight failure rate of the -7 down to the -8, then that’s all one can expect. Trying to educated all the pilots about watching TAS and not exceeding it has not been effective.

[Kolg]

Originally Posted by jask

…. I was at Anti Splat recently getting the bearing upgrade. He has some fixes for the 7/9 to strengthen the forward vertical spar attach point. He feels that is the failure point in a rudder event. BTW, I have toyed with being a novice machinist for the past 20 years and Allan is really good. He also gave me some #9 lead shot to put in my steps.

I’m building a 9A and intend to put shot or sand in the steps. How will you seal the drilled hole?

[rv6ejguy]

I think this has been a educational thread, both about the importance of airplane limits and what can be done should you wish to increase margins on a -7.

[airguy]

Originally Posted by Kolg

I’m building a 9A and intend to put shot or sand in the steps. How will you seal the drilled hole?

I used sand in mine for a "dead blow hammer" effect to dampen the vibrations. I sealed the hole with some epoxy, and then put a strip of non-slip material on top of that.

[airguy]

Originally Posted by rv6ejguy

I think this has been a educational thread, both about the importance of airplane limits and what can be done should you wish to increase margins on a -7.

The two primary ways to increase the margins of ANY aircraft...

1) Hire a competent engineer to find the weak points, and be ready to write the check.
2) Buy an airplane with the flight envelope you want, and be ready to write the check.

[rv6ejguy]

I agree.

There are aircraft better suited for aero and high speed than RVs if you're looking for higher margins.

Looks like the 2 high profile -7 breakups were caused by pilots hooning around with nary a thought of any airframe limits- 234 and 244+ knots respectively- WAY over Va and Vne.

If you want to do aero, get some training first. Things can get out of hand fast with the nose pointed down if you screw up.

[Snowflake]

Originally Posted by jask

He has some fixes for the 7/9 to strengthen the forward vertical spar attach point. He feels that is the failure point in a rudder event.

While the vertical stabs have failed in these accidents, it's happened after other items failed first (ie. the rudder). The forward spar on the vertical stab is a red herring. Reinforcing the attach point of the vertical stab as AntiSplat suggests just creates stress concentrations elsewhere.

[RV7A Flyer]

Originally Posted by grubbat

In my humble opinion, having to use TAS when flying a RV coupled with a narrow margin rudder is a recipe for more inflight failures in future. Data is not emotional and it’s going to happen. That’s just the way it is. Education to individuals may slow the occurrences but relying on human memory is just not good mistake proofing. How far does one go? Well, if a rudder change will bring the inflight failure rate of the -7 down to the -8, then that’s all one can expect. Trying to educated all the pilots about watching TAS and not exceeding it has not been effective.

I think most modern EFISes can display the correct IAS redline for any altitude. I know my Dynon does. And it will yell at me if I hit that speed.

I also don't know that the flutter margin is "narrow". Seems like the two incidents with the most data were at least 15-20% over Vne. How much margin do you need? The Canada incident occurred around 2000', so TAS ~= IAS anyway. The NZ one was between 2000 and 4000 feet, from what I can glean.

This is not a matter of training, it's a matter of pilots grossly exceeding the design limitations of the aircraft. Trust me, if you somehow create a 50% flutter margin (flutter onset at 300 knots), somebody out there is going to go out and find that limitation and kill themselves.

You simply can't engineer away all risk. Stay within the envelope.

Unless and until someone does a better job of *actual* engineering and analysis than the aeronautical engineers at Van's did with their design, all the rest is really just TLAR guesswork.

[RV7A Flyer]

Originally Posted by rv6ejguy

Looks like the 2 high profile -7 breakups were caused by pilots hooning around with nary a thought of any airframe limits- 234 and 244+ knots respectively- WAY over Va and Vne.

LOL! I hadn't heard this expression, and actually had to look it up, but I like it! Something about it makes me laugh out loud...