highlander84

TT39 Fan problem... 4th time...it would seem something is wrong here... This is the 4th time the bolts holding the clutch to the fan have sheered... the 1st 3 times it happened were right together. now about 20 flights latter it has done it again. beings this is the 4th time it’s a new fan again beings there aren’t any holes left to bolt the clutch on... Does anyone have an idea of what is causing this? I hear it sheer in the air but it basically locks the clutch and bell together soI don’t lose power during flight. I knew exactly what had happened. when I pulled the engine out I noticed one of the 4 engine mounting bolts was not in all the way although it was tight... I’m lost. I think it has to be alignment or just material failure of the bolts? Anyone else?

BarracudaHockey

My Feedback: (11)

There's a couple of things that cause this.

1. The bolts are too tight
2. The bolts are too loose
3. High speed vibration

There were a few fans, though I thought they were the early run of 50 size fans, that didn't have the holes tapped deep enough, this would let the screws feel like they were tight but actually they were bottomed out and the resultant gap caused them to shear off.

When you get your new fan screw in the bolts till they bottom out and measure the gap, and the thickness of the fan with a micrometer if you have one, and make sure the bolts will tighten down properly. If thats ok then put them in with locktite and make sure they are 1/8th of a turn past snug and let it sit 24 hours for the threadlock to dry.

highlander84

I like #1 and #2 altho I think my cause is most likely #1 as the heads were deformed. So when my new fan comes in i will do just that. This is very annoying. Now I cant fly for 2weeks boo