Form 337...when's it needed?

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pwttogfk

Well-Known Member
So...my adventure in aircraft ownership continues! Had someone attempt to tell me that the $12 tailskid we have installed on our Cessna 150 is a "major alteration" requiring a Form 337. Just looking at the FAA's own flowchart from AC 120-77 makes it seem like it isn't a major alteration. Opinions?
 
pwttogfk said:
So...my adventure in aircraft ownership continues! Had someone attempt to tell me that the $12 tailskid we have installed on our Cessna 150 is a "major alteration" requiring a Form 337. Just looking at the FAA's own flowchart from AC 120-77 makes it seem like it isn't a major alteration. Opinions?
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I would agree. However, that's a pretty common experience. I think a lot of people like to say you need a 337 because they never really learned when one is actually required and feel like it somehow covers their butt.
 
Makes sense to me...unfortunately we had a lease deal fall through because of it. I love know-it-alls.
 
Just as an aside, we used those tail skids on our 152's for a while and I ended up removing them. With just the ring a tail strike means you have to replace the ring sometimes. With the tail skid a tail strike meant the piece inside the tailcone that the ring screws into is torn through the bottom skin and patching ensues. This happened on all three airplanes we put them on, on one it happened twice.

I don't have any explanation for it really, my theory is that the leverage that the tail skid has is greater than the ring alone.
 
trafficinsight said:
Just as an aside, we used those tail skids on our 152's for a while and I ended up removing them. With just the ring a tail strike means you have to replace the ring sometimes. With the tail skid a tail strike meant the piece inside the tailcone that the ring screws into is torn through the bottom skin and patching ensues. This happened on all three airplanes we put them on, on one it happened twice.

I don't have any explanation for it really, my theory is that the leverage that the tail skid has is greater than the ring alone.
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I dunno... if an airplane hit the tail skid that hard I can't imagine what the damage would be like if the tail skid were not there.
 
Blackhawk said:
I've seen the damage to both as well in a 172. The damage for replacing a tail skid was minimal. The damage without it was significant.
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We had a tailskid on the 172 too and we left that one there, damage was never as bad on that as the tiedown ring mount is a different design. The worst damage I saw on a 172 was when someone had had a tail strike that broke the ring and tail skid off, and then had another one which ground down the skin... that's talent! we patched the skin in that case and screwed another ring and tail skid in and everything was good to go.

I kinda wish I had taken pictures of the damage to the 152's. The tiedown ring screws into a welded steel piece that rivets to the aft bulkhead (in the sheet metal bulkhead airplanes, later ones had a beefier cast bulkhead, more like the 172). With the tiedown ring only I've seen tail strikes hard enough to break the ring off, or at least bend it pretty good and the steel piece was either fine, or was slightly loose, requiring some rivets to be replaced. Each time a tail strike happened with the tail skid installed the steel piece was torn through the skin and hanging there, or completely missing.

You don't have to believe me, it's just what I experienced. I no longer recommend tailskids on 152's because I think the solution is worse than the problem.
 
The biggest reason we've left ours on is because our hanger has a concrete "lip" on the edge, when we push the plane over the lip sometimes the tail comes close to hitting the ground if we push it fast enough. As far as landing, I'm an aeronautical ninja who would never need a tailskid :p
 
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