RV tip over (flip upside down)

[David-aviator]

Originally Posted by osxuser

Yeah, that Ercoupe that they did the testing on is still somewhere at CCB if I'm not mistaken.

Speaking of Ercoupes, anyone want and Ercoupe project? Have one sitting in my hanger right now... relitively complete, and relitively cheap...

...relatively cheap...I'm bet. Would you pay someone to move it?

Years ago while working as an apprentice A&P, I was asked to see if an Ercoupe residing in a patch of weeds could be rescued. It had been there for some time and was a mess. I worked dilegently cleaning out birds nests, replaced some fuel hose and pumped up the tires and finally got the engine running (much to my surprise). After some slow taxi tests, it went roaring down the grass strip and almost flew, but I chickened out at the last minute. Flying it, at that final moment, did not seem like a good idea.

The airplane, with it's B-25 tail is rather cool. Someone eventually bought the thing and trucked it out. The two old farmers who had owned it were not pilots and it never flew while they owned it.

I wonder how many Ercoupes have been flipped? It has a robust nose gear.

[allbee]

Well steve, I'm not flying an RV yet. But I am flying a kitfox and the answer is tough to answer. I know at altitude and slow flight that if I have no pitch and slow and pull power and pull back on the stick, I cannot stall the kitfox. If I have airspeed and pull back and give it up pitch and then slow it and pull back on the stick it stalls. Don't know if this helps you understand on landing the RV or not. But I think if you come in and round out the rv and let it bleed off and then pull up slightly and do and nice round out with a slight flair nose off the ground you can hold it off rather nicely. On the other hand if you hold off and then pull back quit a bit then the pitch is high that aircraft will stall out and the nose will drop like a rock. Just my observations with the kitfox. ONce the aircraft stops flying, it's done. If I had the example you where discribing, I would probably give it a little sugar(power) on touch down and pull back on the stick as the mains touch, keep a little sugar and lightly put on the brakes to keep airflow over the elevator. Bring it to a slow crawl and still keep the nose up, don't know. I will have to see what my 7A will do when I start flying it. But I will have fun learing it, can't wait. Oh and by the way, I'm installing Grove brakes and wheels all around. Goes with the masters as well.

[rvbuilder2002]

Originally Posted by Captain Avgas

A check of the NTSB data base (last 5 years) reveals that RVAs are 5 times more likely to suffer a gear collapse (and virtually every "gear collapse" is in fact a nose gear collapse) than a Cessna 172. This is based on projected average flight hours of 50 per annum for RVs and 150 per annum for Cessna 172s.

That's very interesting when you consider that Cessna 172s are the favourite American trainer....and virtually no-one ever learns to fly in an RV.

Sure you can take off the nosegear from a Cessna....but it's a LOT easier to do it in an RV and any assertions to the contrary are without foundation.

I agree that flight hours per year must be consider when comparing the data but I strongly disagree with your estimate of flight hours per year for the average C-172 versus the average RV. Where did you get these #'s?
Is it published data?

I also disagree with "but it's a LOT easier to do it in an RV and any assertions to the contrary are without foundation".

This can be excepted as an opinion only, because there appears to be no actual data to back it up. With out knowing the actual flight hours per year of all currently registered (and flown) single engine certificated aircraft, and RV's, this type of a statement can not be stated as fact.
I believe it is far closer to a similar percentage of this type of accident per flight hour. In general I think an airplane like the C-150 or 172 should have a better record because as designed they are a lower performance more forgiving airplane

[osxuser]

Hey, I'm not saying it WASN'T pilot error. I cracked a couple of pieces of our cardinals nosegear in a bum landing at Cable. And i've seen a guy collapse the nosegear on an Archer before too. Of course, that was after he porpused it off the nose the THIRD time.

I just say the pilot needs to be innocent until proven guilty. The Cessna/Piper nosegear it's sufficienly proven that, to collapse one, it is assumed pilot error. The RV nosegear has proven weak enough that I assume airplane malfunction...

[hngrflyr]

Speaking of Ercoupes, A couple of friends of mine have resurrected one from storage and have it more or less airworthy. About a month ago, I test flew it. It's a strange airplane. I'd never flown one in my life. When I landed, the wind had shifted and was about 16 KTS at about 80 degrees to the runway. It's crazy landing while crabbing into the wind. Maybe beginner's luck, but the landing was a greaser. I believe this was the first nosewheel airplane I've flown since about 1979. I did come back from the flight with a small punch list of things to fix.

[jcoloccia]

Originally Posted by David-aviator

I wonder how many Ercoupes have been flipped? It has a robust nose gear.

Actually, I wonder how many aircraft flip due to nose gear failures in general.

To get back to RV's, the crux of the issue doesn't appear to be the collapsing...it's the subsequent flipping. If it just collapsed and slid on the nose I doubt this would really get any attention. It's only because it flips and people have gotten hurt (or worse) that anyone cares.

So I get back to the idea that maybe strengthening the gear isn't the right thing to do at all. Maybe what it really needs is weak points designed to shear when overloaded. It's not uncommon for failure points to be built into a design so that the parts fail in an orderly way.

It's like crumple zones in a car. Unless ya'll know something I don't, there's no doubt that the vast majority of car accidents are "pilot error". That's totally beside the point. The primary concern is protecting the occupant, not assigning blame.

Looking at it from another direction, I doubt if most of us have the engineering background to really analyze the dynamics involved, design a "solution" and then TEST it to know that we've actually done anything useful (or at least that we haven't made something worse). Testing seems like it would be a very expensive proposition. This really is the true spirit of homebuilding and experimentation...all I suggest is we be very careful 'cause we're treading in potentially dangerous territory. Someone's gotta do it, right? My hat's off to you.

And I still haven't seen anyone give a precise definition of the problem. Does the gear partially buckle allowing it to dig in? Does the wheel pant have to fly off first? Does the leg turn sideways and then friction between the tire of the ground cause the flip? Maybe THAT'S why it happens on rough surfaces?? Unload the leg for a second, it turns sideways and lands crooked with high loads, possibly jamming the yoke? I dunno. There's a lot of speculation on causes and solutions but it's just speculation.

And then again, the vast majority of RV's flying seem to be just ducky 100% stock.

For the record, I'm not picking on David at all. I've just been reading all of this stuff for a couple of weeks and the quote got me thinking about how little we actually know about what's going on. I don't even think we have enough information to say that there's a problem compared to other GA aircraft. Collapses per landing categorized by landing surface for RV's vs. Cessna's/Pipers? I don't know that number.

I've got no skin in the game as I wasn't building an -A, and I'm not even building an RV anymore but for my money I'd be concentrating on a root cause investigation before worrying about how to solve it.

*off my Bearhawk building, rag and tube soapbox*

[kentb]

Originally Posted by Steve Sampson

I have asked this several times but no one ever answers. What do those with superior nosedragger skills, or appropriate training, do to avoid flip over accidents, once the full up elevator will no longer keep the nosewheel off the ground? I have only ever steered at that stage, (with the stick full back)but clearly I am missing something.
.

Once the nose wheel comes down, avoid using the brakes. Use the rudder as long as you have authority and then light braking only. Using the brakes puts more loading on the front gear. The extra loading will amplify any surface problems that exist.

If you are using lots of brake, then you made a bad approach and should go-around. If you aren't lined up with the runway or land to long and try to use all the brakes you have to correct expect to increase you tip-over risk.

I don't think that the nose gear is perfect, but I would not be willing to sacrifice any speed for a stronger gear. The problem is that the gear can tuck under if the forward speed is sufficient and there is an obstruction of some sort and the gear has enough loading on it.

If the gear were made stronger, I don't think that would change anything. The gear might not bend, but instead the firewall would take the damage.
A larger tire will ride over obstruction better, but will cost you speed.
A skid might help unload the tire, but I am not sure of that.

Kent

[RVbySDI]

In my opinion the problem with the nose gear collapse and/or nose over accidents are not due to an inefficiency of the nose gear leg. Instead it is due to the fact that the leading link yoke/fork is too (that is t double ooooo) close to the ground. The gear leg is designed to flex. That is the only shock absorbing quality of the current design. When that yoke that is sitting too (again with that t double ooooo) close to the ground has an opportunity to come into contact with some stationary obstacle, such as the ground, because of whatever reason, lets say. . .

Pilot error (click)
Pilot error (click)
Pilot error (click)

. . .the nut at the bottom of the yoke, that just happens to be the closest thing to the ground, digs into whatever it comes into contact with. If the force is big enough this is transferred up the gear leg. The gear leg will then fail at the weakest point (which usually happens to be at that tapered point part way up the leg).

It is my opinion then that the close proximity of the leading yoke to the ground is the true culprit. Too (dad blast those t double oooo's) much flex from a rough surface, too (hmmmm) much speed at taxi over said rough surface or some other various form of

Pilot error (click)
Pilot error (click)
Pilot error (click)

and the nut digs into the said rough surface.

The solution seems to be to get that ridiculously low slung leading link yoke/fork higher up off of the ground and put a larger tire under all that metal to allow for an opportunity to roll over any hole rather than sink into it. Now most speed demons are opposed to that because it will mean placing more surface into the air stream thus inducing more drag. For those with this speed requirement I say stay with the current design. LONG LIVE THE KING OF SPEED!

However, for any others like me who find that giving up 1 or 2 (h, e double hockey sticks, I'll even give up 3) knots is a welcome compromise to mitigate some of this nose over risk, lets look at this solution. Moving the yoke further away from the ground and putting a larger tire under there is going to solve a lot of these issues.

Oh yeah, I forgot the other part. Just like those disclaimers for diets that say things like "results for our super duper diet pill work best when used along with proper nutrition and regular exercise", pilot technique is always going to be the ultimate key to avoiding these accidents. Just like popping pills without exercise will not melt the pounds off, "fixing" this yoke without proper pilot technique is not going to do much either. I would like to hope this solution will go a long way toward reducing the risk of serious damage to my aircraft should I fail to be a good pilot on some inattentive occasion.

My .02 worth and a little comment on plans I intend to work with for my 9A.

Live Long and Prosper!

[Ralph Kramden]

Originally Posted by RVbySDI

In my opinion the problem with the nose gear collapse and/or nose over accidents are not due to an inefficiency of the nose gear leg. Instead it is due to the fact that the leading link yoke/fork is too (that is t double ooooo) close to the ground . . .

Well said ! I have been waiting for someone to succinctly talk this problem through without dismissing it as a purely pilot error problem. About time. Thanks.

--Ralph

[gmcjetpilot]

Standard Off road


High speed version (ain't she purdy)


Incorporates 6 by tires utilizing new materials for the gear legs, un-obtain-inum and transparent aluminum. It will never flip and the speed is the same as the standard RV gear minus 40 kts.