shade tree engine mount repair

Ed Haywood

Ed Haywood

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Jul 12, 2020
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Tampa FL
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Big Ed
This Arrow came into my buddy's shop for annual. Once he washed 7 years of grunge off the engine, he found this repair.

A 9 inch section of a diagonal tube on the engine mount had been cut out. Another section of tube was split in half lengthwise and bolted to the stubs to replace the gap.
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That’s terrifying. Any idea how long it had been that way?
 
That's not even a reasonable attempt at a proper repair. And it probably took longer than it would to do it right.
 
Racerx said:
That's not even a reasonable attempt at a proper repair. And it probably took longer than it would to do it right.
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Doing it right means taking the engine off the mount, then removing the mount from the airplane, and getting it welded up by a trained and competent welder.

Engine mounts are not something to take lightly. What would happen to your CG if that mount failed and the engine fell off the front of the airplane? Would the airplane be able to glide?
 
Dan Thomas said:
Doing it right means taking the engine off the mount, then removing the mount from the airplane, and getting it welded up by a trained and competent welder.

Engine mounts are not something to take lightly. What would happen to your CG if that mount failed and the engine fell off the front of the airplane? Would the airplane be able to glide?
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Engine parting the fuselage results in total loss of control
 
I can hear it now “it’s going to cost how much!!?” “But it worked fine for all these years!”.
 
Dan Thomas said:
Doing it right means taking the engine off the mount, then removing the mount from the airplane, and getting it welded up by a trained and competent welder.

Engine mounts are not something to take lightly. What would happen to your CG if that mount failed and the engine fell off the front of the airplane? Would the airplane be able to glide?
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Fuel hoses and oil hoses could hold it on if not for the tornado of **** that would happen with the prop still spinning. Honestly I’d expect you have a good chance of not living long enough to worry about w&b.
 
My bud has a L-3 with documented history of having LOST its engine on its acceptance flight. Like fell right off, gone, very tail heavy. Engine recovered from a field some time later.

Pilot landed safely. There is no reason you can’t fly a plane that’s AFT cg. It’s just not stable and it’s prolly VERY difficult with ZERO margin for error. But it can be done, providing it does its disappearing act relatively benignly.

I’m impressed it worked for seven years… maybe it’s a viable fix?!!
 
Tools said:
My bud has a L-3 with documented history of having LOST its engine on its acceptance flight. Like fell right off, gone, very tail heavy. Engine recovered from a field some time later.

Pilot landed safely. There is no reason you can’t fly a plane that’s AFT cg. It’s just not stable and it’s prolly VERY difficult with ZERO margin for error. But it can be done, providing it does its disappearing act relatively benignly.
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The pilot would have to instantly stuff the nose down steeply and keep it there with near full-down elevator. The firewall would cause lots of drag.

But the L-3 is a Cub. A Cub can just barely kill you. Something like a 172 or 182 would be a different animal with no engine and prop weight.
 
Salty said:
if not for the tornado of **** that would happen with the prop still spinning.
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I have occasionally pondered: could the prop, as it winds down, carve the front seaters out - should one side of the engine mount suddenly let go and the engine/prop rotates to the side with the residual thrust.

Never heard of it, so I’ll leave that one to the category of ‘sudden awakedness following aviation nightmares’
 
Even in the experimental world I hope nobody "experiments" like that! It took at least two ignorant people to allow that to happen ...
 
I believe some of the small racers that turn high rpm mandate chaining

the engine to the wing spar . W n B purposes if you lose a blade.
 
Dan Thomas said:
Doing it right means taking the engine off the mount, then removing the mount from the airplane, and getting it welded up by a trained and competent welder.
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The really bizarre thing is that it is not that hard to do this. I had to do a similar repair on my Lyc O-235. Four hours start to finish and the engine and motor mount are off. Then its just a matter of finding a competent welder and an hour of his time.

Instead, risk killing everyone on board your aircraft. Should be criminal.
 
Magman said:
I believe some of the small racers that turn high rpm mandate chaining

the engine to the wing spar . W n B purposes if you lose a blade.
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I believe so. I recall a Biplane, sport, or F1 (can’t recall which) landing at Reno with the engine hanging from cables.

There was also Relentless (sport) having the prop come from together. Not a full engine falling off, but still…
 
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I think he should roll that plane onto a tie down and walk away. Nothing good will come from his signature in that logbook.
 
Dana said:
Aerobatic planes often have a safety cable between the engine and the airframe in case the engine mount fails
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My Decathlon did when I got it. My A&P removed on the first annual.
 
Dana said:
Why?
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Dunno. He just said it was bogus. He had a lot of experience with D's, used to maintain Greg Koontz's airshow plane, so I didn't argue.
Decathlons have been doing acro for 50+ years, with 6000 aircraft produced and zero recorded instances of engine departure, so it doesn't seem like a pressing need.
 
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Flatiowa said:
At this point I think the entire aircraft should be considered suspect not just the firewall forward. (There isn’t a 2x4 shoved into the wing to support a cracked spar? Type stuff).
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I believe that's exactly what Piper is gonna have to submit to the FAA as AMOC for their latest spar hole final AD revision.:biggrin:
 
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