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  #1  
Old 04-03-2017, 12:13 PM
boandrv7a boandrv7a is offline
 
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Location: denver
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Default RV-7a Nose-Gear Collapse Part 3 - Video of the retaining pin

Part 3 - I got a bunch of questions about the nose-gear retaining pin. I took a video of the mangled retaining pin (the pieces I could find).

See it here:

https://www.youtube.com/watch?v=6hJx_xsAAFc

Jim
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  #2  
Old 04-03-2017, 03:54 PM
pa38112 pa38112 is offline
 
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Interesting. How many hours are on that bolt? Was a new nose gear leg installed per Vans SB 07-11-09, and if so was the new leg drilled by Langair or by someone else?
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Old 04-03-2017, 05:11 PM
boandrv7a boandrv7a is offline
 
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The plane has a little over 300 hours. There were no modifications made, but I was not the builder and never looked at the bolt prior to the collapse. I did have a pre-inspection done, but this issue was missed.

Thanks!

Jim
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Last edited by boandrv7a : 04-04-2017 at 06:16 AM.
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Old 04-03-2017, 08:22 PM
gasman gasman is offline
 
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The good news is........ IT DID NOT FLIP.

The bad news is this aircraft has not been properly inspected IAW the service bulletins from the manufacturer of the kit.

With the stop installed wrong causing excessive stress on the leg bolt when the wheel hit the stop during a turn or induced shimmy, and maybe the bolt not installed according to the plans, there would only be one end of the bolt to hold back the twist of the leg, a failure of the bolt is expected.

Inspect the nose gear off of the ground at each annual. And check here here https://www.vansaircraft.com/public/service-rv7.htm for any updates.
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  #5  
Old 04-04-2017, 06:17 AM
boandrv7a boandrv7a is offline
 
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Gasman - Thanks for the comment. I agree with your theory!

Jim
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  #6  
Old 04-04-2017, 10:52 AM
Richard@Langair Richard@Langair is offline
 
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Default Breakout force on nose wheel pivot

Jim,
I just watched a couple of your videos including the nose wheel shimmy video you made a year or so ago.

That video showed the front tire swinging what looked like perpendicular the the runway. That makes me think maybe the breakout force on the nose wheel pivot at that time was not high enough. I know the plans show how much force is recommended, and I know of many people that go much higher on the breakout force to help prevent that type fo thing from happening in the case where a shimmy starts.

I dont know of any negative consequences of having the breakout force higher than the plans indicate, but maybe that is something the factory can shed some light on.
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Old 04-04-2017, 11:33 AM
BillL BillL is offline
 
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There was a very good thread with these contributors on this subject a few years ago. I collected the information, references and made a PDF with just the facts.

Contributors (in alphabetical order): Walt Aronow (“Walt” on VAF, RV-7A), Bruce Hill (bruceh, 9A), Bill Palmer (same, 8A in- work), Bill Pendergrass (rzbill, 7A), and Alex Peterson (AlexPeterson, 6A).

Send me a PM via EMAIL and I will send this to you. I tried to get DR to post it to no avail.
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Old 04-04-2017, 01:34 PM
boandrv7a boandrv7a is offline
 
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Quote:
Originally Posted by Richard@Langair View Post
Jim,
I just watched a couple of your videos including the nose wheel shimmy video you made a year or so ago.

That video showed the front tire swinging what looked like perpendicular the the runway. That makes me think maybe the breakout force on the nose wheel pivot at that time was not high enough. I know the plans show how much force is recommended, and I know of many people that go much higher on the breakout force to help prevent that type fo thing from happening in the case where a shimmy starts.

I dont know of any negative consequences of having the breakout force higher than the plans indicate, but maybe that is something the factory can shed some light on.
Richard - The video you reference is not one that I did. If you have a link to it, i'd like to see it!

Jim
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Old 04-04-2017, 03:46 PM
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Raymo Raymo is offline
 
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I may have missed something in the video but it appears the standard bolt was installed but could not take the abuse of the improperly installed limiting bracket on the nose gear yoke. I wouldn't blame the bolt, in other words.
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Old 04-04-2017, 04:20 PM
gasman gasman is offline
 
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Quote:
Originally Posted by Raymo View Post
I may have missed something in the video but it appears the standard bolt was installed but could not take the abuse of the improperly installed limiting bracket on the nose gear yoke. I wouldn't blame the bolt, in other words.
The bolt that Van's calls out for can be a little short...... The bolt just fits through the mount with the threads at the edge of the hole. Take a bolt and measure it just past the threads, it is a few thou smaller than the rest of the shank. So that means that only one side (the head side) of the bolt is holding back shear. It will fail much sooner than if both ends were holding shear.

To resolve this issue, go to the next longer bolt and add a washer under the head. Two will be needed under the nut. Do what needs to be done to get full shank contact..... snug fit at each end of the bolt.
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Last edited by gasman : 04-04-2017 at 04:52 PM.
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