What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Nose gear leg strength

K

[email protected]

I'm New Here
I have been flying my RV-6A for 18 years 1500 hours and have always been apprehensive about the strength of the nose gear leg, now my grandson has started his flying career at 14 learning in the RV.
I again started the conversation about the gear leg strength and was advised Anti Splat build a strengthening bracket. How is it I did not know this. Well I ordered it, got it installed in an hour, what a nice piece of engineering, and I sleep better now when my grandson flies it.
If like me you did not know about the ?nose job one or two?, I suggest you check it out, it could save your life.
 
My uncle pranged my 9A in on a landing hard enough to leave half my nose wheel pant on the runway, I found witness marks on the nose gear leg that showed the Anti-Splat brace made full contact with the flexing gear leg. Did it prevent a failure and noseover? Can't say - but it didn't happen, and I'm glad I installed it.
 
So, I just got done with the transition training for the 9A owner in Tucson. He did well, for a Cessna pilot. I do see the tendency to round out and flare too high in the 9A. This could lead to a big "drop" in landing and then potential impact on the nose gear. This build has Alan's anti-splat under the fairing. And a lip skid. But, my advice for owners is to never even come close to using them. I treat the nose like a glass slipper. Elevator comes all the way aft during the landing rollout... until there just isn't enough elevator authority to keep the nose off the runway. And on takeoff, it comes up almost immediately... and roll along at takeoff angle of attack until it flies off by itself. One takeoff... holding about 75 indicated, resulted in the same deck angle as the 737 that was lifting to our left off runway 11 at Tucson. The new owner was shocked.... to say the least. Cruise climb at about 110 suited him better. I had to throttle back enroute as it was nudging the yellow arc and ground speed was 213. It showed me a Lycon IO-360 and CS prop is just the upper comfortable limit, (for me) on a 9A.
 
Ken,
The nose job is only 1/2 the solution. You also need to modify the nose wheel axel or bearings. I would suggest the Matco axel.

http://www.matcomfg.com/AXLEASSEMBLYA24125INCH-idv-3657-1.html

It is not a hard landing that causes the nose-over. It is the front wheel locking up as a result of a hard landing (or digging into a rut). I the case of a hard landing, the thin Vans axel deflects and puts enough load on the taper bearings to lock them up - or at least that is the commonly accepted theory.
The Matco axel is an $80 solution that takes less than an hour to install.
 
pa38112 said:
Ken,
The nose job is only 1/2 the solution. You also need to modify the nose wheel axel or bearings. I would suggest the Matco axel.

http://www.matcomfg.com/AXLEASSEMBLYA24125INCH-idv-3657-1.html

It is not a hard landing that causes the nose-over. It is the front wheel locking up as a result of a hard landing (or digging into a rut). I the case of a hard landing, the thin Vans axel deflects and puts enough load on the taper bearings to lock them up - or at least that is the commonly accepted theory.
The Matco axel is an $80 solution that takes less than an hour to install.
Click to expand...

Or the Anti Splat stock front wheel bearing mod.
 
I think the Piper Cherokee nosewheel bearing setup is the best design. Uses standard size bearings and an adequate axle. Easy to service, too.

Roberta
 
I turned my RV7A upside down due to a stupid landing on my part. I had the AntiSplat on my nose gear. The moral of the story do not land on the nose gear. I think it will be good until it isn't. Do not rely on something else to keep you out of trouble.
 
There are a couple of NTSB documents out there (if I understood the steps in the dance a little better, I'd upload these - if you need the entire document(s) send me a PM):

One -
STRUCTURES STUDY
NTSB Case No.: ANC05LA123
Location: Palmer, Alaska
Date: August 12, 2005
Airplane: Van’s Aircraft RV-9A, N63EB

Two -
VANS AIRCRAFT MODEL A SERIES AIRPLANE
NOSE-OVER ACCIDENT
PHOTOGRAPHS
June 21, 2007

From the summary of the first document:
"...Once the strut and fork have contacted the ground, the strut will bend aft. The aft loading from the dragging fork and the spring-back reaction of the strut produces an overturning moment and lifting action that may result in the airplane overturning without any additional forces acting on the airplane. The aerodynamic load on the horizontal stabilizer may prevent the airplane from overturning while the airspeed is greater than some critical yet presumably low airspeed....The FEA shows that the nose gear strut has sufficient strength to perform its intended function. In all cases, the landing gear struts and forks were making contact with the ground and initiating the damage sequence...."

I thought a lot about the nose job, but have always kind of wondered about the stress transfer to some other part of the gear or mount when it makes contact with the gear leg.

Dan
 
Last edited:
DanBaier said:
I thought a lot about the nose job, but have always kind of wondered about the stress transfer to some other part of the gear or mount when it makes contact with the gear leg.

Dan
Click to expand...

You throw your money on the table and pick up the dice. I much prefer to keep the airplane on the gear (assuming that's possible, in my case it was) and look for stress/problems in other parts of the airplane after the incident. At least that way you save a prop and engine teardown at a minimum.

As Allan says in his documentation on the website for this product - by the time the anti-splat device comes into play, other things are already breaking and this is intended to minimize further damage, not avoid it. It's like having a seatbelt/airbag after the bumpers are already crumbling. It certainly won't stop the airplane from nosing over under all scenarios - but there are certainly some that it will.
 
Last edited:
DanBaier said:
I thought a lot about the nose job, but have always kind of wondered about the stress transfer to some other part of the gear or mount when it makes contact with the gear leg.

Dan
Click to expand...

I think one positive effect of the nose job, once it is engaged, is to transfer deflection to a point much higher up on the gear leg, which could change the whole dynamic following an abrupt high-load landing event. When the deflection occurs low on the gear leg, it bends in a way that further lowers the nose as the fork rotates upward. There is a positive feedback, CG-related point of no return where the lower gear leg is overwhelmed and yields, further dropping the nose of the aircraft and ultimately putting it on its back. Moving the deflection point higher on the gear leg instead raises the nose, and in many instances may prevent entry into this positive feedback loop event.

I’d be curious to see data on the CG condition of RV’s that have suffered this fate. I’ve never been a fan of excessively forward CG loading of RV’s because of its negative impact upon nimbleness in maneuvers, and as others have stated I endeavor to use the nose wheel only for taxiing and never for landing. Staying off the brakes during the initial rollout is also a good idea because it contributes further to the nose-down moment. I even taxi like a tailgragger with stick full aft to reduce wear and tear on the nosewheel, but I am still installing the nose job now as part of a series of mods. With or without the nose job mod, I do not think there is cause for much concern about damage to structures other than the nosewhel and its leg from most hard landings(other than endong up upside down!). The gear leg mount is quite stout.
Otis
 
Last edited:
You must log in or register to reply here.
Back
Top