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RV-7a Nose-Gear Collapse Part 2...

boandrv7a

Member
For those of you who PM'd me and asked questions, here is an updated video now that the engine has been removed and more damage revealed:

The AV8R's

BTW... The nose-gear bolt WAS sheared and the nose-gear stop flange was installed incorrectly. I don't know if that had anything to do with it, or not, but for those who were wondering...

Thanks!

Jim
 
That happens to me sometimes... I find that if I wrap my head in tinfoil, stand on one leg and hold hangers in both hands, it works...

Jim
 
No information in this video other than what a nose gears looks like when you land on it or maybe have the aircraft severely crabbed at nose gear touch down. The opportunity to learn is what was experience in the windy conditions, was it a cross wind, what was the wind speed, was there some type of shear and how did the aircraft respond to pilot input in those conditions.

As far as gear failure on its own we have all seen years of this issue and know the gear just does not fail on roll out for no reason. Is the RV nose gear less forgiving than a Cessna 150 when you land on it, absolutely.
 
http://www.vansaircraft.com/pdf/sb14-12-22.pdf

If I'm not mistaking, SB 14-12-22, which came out over 2 years ago, was the result of an incorrectly installed stop flange which caused the NLG retainer bolt to fail.
This was likely a contributor, or possibly the direct cause of, the failure in this case as well.

From the SB:

"Van’s Aircraft has received reports of damage resulting from the WD-631-PC or WD-1031 Nose Stop Flange (stop flange) having been oriented incorrectly during installation. If the stop flange is installed incorrectly, it will allow insufficient rotation of the nose fork during tight taxi turns and can cause the tire to drag sideways. This induces excessive loads on the stop flange, nose gear leg, engine mount and the associated attach hardware."
 
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If the bolt was installed wrong you are correct but I would think if true in this case there would be evidence to that end.
 
If the bolt was installed wrong you are correct but I would think if true in this case there would be evidence to that end.

The stop flange was incorrectly installed as can be seen in the video and confirmed by the OP, this can cause the upper retainer bolt to shear with the resulting nose gear collapse.
 
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My apologies, Walt is correct, I do start to get a little defensive of the RV nose gear incidents as most are usually do to a nose gear landing.
 
No information in this video other than what a nose gears looks like when you land on it or maybe have the aircraft severely crabbed at nose gear touch down. The opportunity to learn is what was experience in the windy conditions, was it a cross wind, what was the wind speed, was there some type of shear and how did the aircraft respond to pilot input in those conditions.

As far as gear failure on its own we have all seen years of this issue and know the gear just does not fail on roll out for no reason. Is the RV nose gear less forgiving than a Cessna 150 when you land on it, absolutely.

Hey Pat - Sorry, I was not flying the plane when the incident happened, so I'm not certain what the actual conditions were and what mistakes were made. The pilot said he bounced and the conditions had gone from calm to gusty.

Jim
 
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Nos gear

Vans has been flying RV 6 A's, RV 7A's, RV 8A's and 9A's for many years and as far as I know I has not experienced a nosewheel failure. This suggests that there is a pilot factor that comes to play in many of these failures. Some of the underlying damage may have been done on prior landing attempts that did not go perfectly well. If this happened to me I would be sure to have additional instruction and practice in proper technique of minimizing loads on the nose wheel occurring on landing. Also might install the Anti Splat mods. Hope that no one suffers a repeat...
 
Im willing to accept that 100% of the nose gear failures is either pilot or builder error. That does not change the numbers on how many nose gear failures there has been. Making them stronger to be able to handle a bit more abuse would not be a bad thing. I don't think there are many things that have ever been built that can't be improved. The 10 gear is better and the 14 gear is an upgrade too. This is NOT a dig on the original design of the gear. It was designed to be light, not taxied on uneven ground, and to be held off the ground until you are parked. It works great for the design goals.

I am still taking lessons and I know if I had landed my 9A the same as I landed the 172 yesterday, I would have rolled the gear and gone over. If I had the engineering skills, I would try to redesign the mount and gear to make it stronger. If it cost 10 pounds - I would be ok with that. I have a FP Catto and a light battery so my nose weight would still be fine. I appreciate Alan for the AntiSplat bar and nose wheel bearing that I am installing on my plane.

As I get closer to completion, I am looking to install larger tires that can handle a bit bigger bump on the taxi way or runway. I will be taking transition training and get my license before I finish, so I still have a chance!

This is probably the plane I need! https://www.youtube.com/watch?v=Qa12veWQEgU&index=2&list=PLKkHlxLaos3W7voGdGc_mpmubIneBskiB
 
One thing I have do on my annual condition inspection is change the nose gear bolt,washer and nut. I will do it every year. I also pull the nose gear out and inspect for cracks etc. This gives me a good look at the bolt to see if there is any evidence of gouging as if it had tried to shear! Or had a shear load on it. So far so good!
 
Taper Pin

Last year when I had the engine off, I did the taper Pin mod where
the nose gear mounts to the engine mount. There is no slack now, like
there is with a bolt. I already had all the AntiSplat nose wheel mods
in place. Always taxi with stick all the way back, as well on beginning of
take off roll.
 
http://www.vansaircraft.com/pdf/sb14-12-22.pdf

If I'm not mistaking, SB 14-12-22, which came out over 2 years ago, was the result of an incorrectly installed stop flange which caused the NLG retainer bolt to fail.
This was likely a contributor, or possibly the direct cause of, the failure in this case as well.

From the SB:

"Van?s Aircraft has received reports of damage resulting from the WD-631-PC or WD-1031 Nose Stop Flange (stop flange) having been oriented incorrectly during installation. If the stop flange is installed incorrectly, it will allow insufficient rotation of the nose fork during tight taxi turns and can cause the tire to drag sideways. This induces excessive loads on the stop flange, nose gear leg, engine mount and the associated attach hardware."

To me, and I am an aerospace structural design engineer, this gear failure looks different then others as it looks like it failed due to more side loads then the others. The gear is bent to the side as apposed to others are straight aft.
Like any engineer should admit, my opinion is an opinion and only based on the very limited view I observed from the video. When I just watched the part 2 video there was no video of the nose gear off the aircraft. Was this edited out?
 
The stop flange was incorrectly installed as can be seen in the video and confirmed by the OP, this can cause the upper retainer bolt to shear with the resulting nose gear collapse.

Just to amplify what Walt has said - if the flange is incorrectly installed, every single time one does a tight turn while moving the plane or taxiing, the nose wheel is prevented from pivoting far enough by the flange. This causes a large torque to be transmitted up the gear leg, which can only be resolved by the mounting bolt.

A properly installed flange will allow the nose wheel to pivot far enough so that the airplane can be turned with one main gear not moving.
 
To me, and I am an aerospace structural design engineer, this gear failure looks different then others as it looks like it failed due to more side loads then the others. The gear is bent to the side as apposed to others are straight aft.
Like any engineer should admit, my opinion is an opinion and only based on the very limited view I observed from the video. When I just watched the part 2 video there was no video of the nose gear off the aircraft. Was this edited out?

I had the nose-gear and engine mount over at the A/P, so I didn't get any video of it, but I will.

Jim
 
I also went the taper pin method, does anyone know if this pin has the same strength as the AN hardware it replaced, it is a larger diameter so maybe stronger?
 
I also went the taper pin method, does anyone know if this pin has the same strength as the AN hardware it replaced, it is a larger diameter so maybe stronger?

Bret, if you have an extra taper pin, take a file to it and to an AN bolt. The harder one has a higher tensile strength (not accounting for diameter differences, if they exist). Also important in the taper pin design is that the holes are tapered equally (matching) to the pin, and are complete. One wants both ends of the pin to see the shear equally.
 
I bought all the taper pin hardware from Aircraft Spruce, so I hope it is of the correct grade.......:rolleyes:
 
One scenario

...this gear failure looks different then others as it looks like it failed due to more side loads then the others. The gear is bent to the side as apposed to others are straight aft.

If the bolt sheared, the leg can rotate causing the sideways loading.

As to the gear's durability, doesn't Vlad fly the stock nose gear without any aftermarket bits? If so, given where he has gone with his -9a, that is an huge endorsement for the durability, simplicity and functionality of the stock design when flown right.
 
In the video it also looks like the old Matco wheel with the bearing spacers that have been known to pinch the bearings during heavy load conditions and cause the nose wheel bind and pull the nose leg under till the front of the fork snagged on the surface of the runway. This, along with a failing bolt due to an improper installation of the stop, could have caused this.

I don't think this situation is entirely pilot error. On the RV6 plans, you had to look really hard to find the one and only sketch of how the stop was to be installed. So I can see how there are many installed wrong...... It just looked right.

The other problem that came along with the RV6 was a change from a Cleveland wheel to a Matco wheel some time before 1998. The problem with that wheel and axle is well documented............. It just proved to be a bad combination.
 
Just an FYI, I use NAS6605-28 bolts to replace the standard AN5 when I have them out, the NAS is a good deal stronger than the AN counterpart
(160K vs 120K I believe) and it's a few thousands larger which helps make it a tighter fit.
 
I figured out my problem

I'm not getting any audio on your videos. Other YouTube videos work.
I fixed my computer problem. My sound card was set to 5.1 surround and I only have two speakers. I set it to "stereo" and now I can hear the audio along with your video. Previously I could only hear YouTube videos that were encoded in 5.1, but not stereo. Who knew?
 
2/11/17 Nose Gear Incident

It just so happens that I was cleared to land #2 behind the incident airplane. I've been debating whether or not to give my very brief view of what I witnessed that day...

Let's start with the day before. We attempted to go to Greeley for breakfast, but it was so bad we wound up turning around and headed back to FTG. LLWS was all around us and we saw 40 - 50 kts winds a thousand feet off the ground.

The day of the incident the winds were out of the ENE. (we were using runway 080) I don't recall exactly what they were, but it was starting to get gusty and the winds were picking up (certainly above 15Kts) I headed out to do a few TNG's, I don't have the exact time, but it was somewhere after 10:00 AM.

I had taken off of runway 8 and was in left traffic for a TNG. The tower cleared me #2 after the RV ahead of me. I spotted him on final as I turned base, as I was making my base to final turn he seemed to be about to touch down. Wasn't paying too much attention as I was flying my plane....

The next thing I notice, is the incident aircraft is in a sharp left (90 degree) turn and headed for the grass. At that point, it APPEARED to me that it was still on all three legs. It didn't look like it nosed over till it hit the edge of the runway/grass. By that time I was on the radio to the tower, telling them the RV went off the runway and I was going around. FWIW that's all I saw. :(

A Photo of the plane being towed.

FTG Bent Gear by Scott Mills, on Flickr
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