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  #1  
Old 03-21-2021, 11:25 PM
Lyle RV8 Lyle RV8 is offline
 
Join Date: Apr 2014
Location: Davis, Ca
Posts: 19
Default Maintenance Induced Failure

Recently a maintenance error caused a serious inflight emergency in my RV-8.

While descending to land at Santa Barbara, about 15 miles west at ~3,500 ft, I encountered severe turbulence, likely a mountain rotor given the wind conditions. After enduring the turbulence for a minute or two I was coming to the conclusion that landing at Santa Barbara was not going work. Just then the plane was tossed even more violently and my head was slammed against the top of the canopy. I went to (re)tighten the seatbelts and found the left lap belt had failed, it was no longer attached to the airframe.

Even being dazed by hitting my head I realized this was a serious emergency. Without a functioning seatbelt the continuing severe turbulence was tossing me around inside the cockpit and I was concerned that hitting my head again, which seemed likely, could result in a concussion or unconsciousness. I initiated a full power climb to get out of the rotor. It probably took less than a minute to reach smoother air but it felt like an eternity. I was very lucky to exit the turbulence without a serious head injury.

After landing at Santa Ynez the problem was obvious. As can be seen from the attached picture, the bolt that secures the left lap belt is in place but the seatbelt bracket/strap are missing. I had installed the bolt with the seatbelt bracket offset and the bolt did not go through the mounting hole in the bracket. It must have been that way since the last annual inspection 11 months ago (during annual I remove the front seat and seatbelts to facilitate the control linkage inspections). Apparently, the left lap belt bracket had been held in place by compression from the seatbelt mounts and the bracket lodging against the seat back. Surprisingly it had held quite well that way for many flight hours but let go in the severe turbulence.

While Iím embarrassed to admit an error on a seemingly simple system, I felt it worth sharing. A reminder that even simple systems, like seatbelts, require your full attention.
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  #2  
Old 03-22-2021, 02:17 AM
kiwipete kiwipete is offline
 
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Location: Birmingham United Kingdom
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Default

Lyle

Glad to hear you landed safely. Thanks for sharing, we all can learn from what seems a simple oversight.

Peter
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  #3  
Old 03-22-2021, 04:30 AM
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rv8ch rv8ch is offline
 
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Thanks for flagging this, Lyle - I can see how that happened. I'll check mine before the next flight.
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  #4  
Old 03-22-2021, 05:18 AM
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Steve Melton Steve Melton is online now
 
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agree, that was a serious condition.
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  #5  
Old 03-22-2021, 05:25 AM
Desert Rat Desert Rat is offline
 
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Default

Thanks for posting this. It's hard to confess something like this, but it's extremely helpful others.
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  #6  
Old 03-22-2021, 05:51 AM
Ron B. Ron B. is offline
 
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You know, how many people will say "how the heck did he do this, this could never happen to me". It can happen to anyone.
Thanks for posting.
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  #7  
Old 03-22-2021, 05:54 AM
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MacCool MacCool is online now
 
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During my recent condition inspection I removed my Crow restraints so I could scrub them up. Reinstalling, I misaligned one of the belt attachments in the same way, discovered by a good tug on the belt after tightening the bolt. I thought that error was surprisingly easy to make.
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  #8  
Old 03-22-2021, 07:11 AM
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airguy airguy is offline
 
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Just this past week I reinstalled my seat belts after some work during the annual and came to the same conclusion - this is easier to do than you would think.
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  #9  
Old 03-22-2021, 03:37 PM
Lyle RV8 Lyle RV8 is offline
 
Join Date: Apr 2014
Location: Davis, Ca
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Thank you for the nice responses.

Today I recreated the assembly error as I couldn't understand how the seatbelt had not pulled out of the mount much earlier. See the picture labeled WRONG. What surprised me is that with the seatbelt bracket held vertically by the attach hardware and resting against the seatback I could not dislodge lap belt, no matter how hard I pulled. That explains how it held in place for 11 months, including flights in moderate, but not severe, turbulence. A visual inspection was the only way to find this error.
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  #10  
Old 03-22-2021, 05:34 PM
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thatguy thatguy is offline
 
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Always a reminder to use feel AND sight when assembling things.

Similar mistakes can happen in completely other ways too. For example, screwing a bolt into something that has messed up threads is sometimes not obvious except for that it will feel tight long before it actually is tight. In this case the only way to tell is a visual/manual inspection to look for looseness. Fortunately, if you're not sure you can always chase the threads with a tap but without suspicion, no one would do that (unless specifically instructed) before attaching a bolt. This has happened to me a few times in the manufacturing industry because you can run into a few bad inserts or nutplates here and there.
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