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Q-talk 103 - Smokin' Prop

I admit it - I ruined my prop - MY FAULT! - but, there is a message for everyone. N321TM's 60X72 Amar-Demuth prop is toast after one flight too many before rechecking bolt torque. Yes, I knew it was due. Yes, I had a new digital torque wrench (at home rather than in the hanger), but it was a nice day, and it could go one more flight, right?

Well, at 11,500 ft, I picked up a slight vibration at full power. It smoothed out at 2500 RPM and the downhill run to Livermore was fine. On the ground, it sounded like a broken exhaust pipe. On shutdown, it was a loose prop with two broken bolts. Again, blame is to me for flying with an item I knew was due for inspection. Later, I talked to prop makers, Mike Demuth and Craig Catto. Both said that the fiberglass rear spinner bulkhead was a no-no, as the glass can heat and move, resulting in loosening bolts. Demuth said I could have torqued before flight and still have the same thing happen. In this case, I don't agree with him as the bulkhead has proven itself and I should have checked torque. For you builders and new flyers, think about replacing a glass rear bulkhead with one made of metal. I'll be going to metal on mine.

Demuth was booked up until May - ouch! Catto is working some other props for people in Livermore, so I'll have one in a couple of weeks. It was an expensive flight; new prop, new extension and new bolts on order.

One thought from David Gall on the Q-List: If just one flight too many past the due date was all it took to toast the thing, maybe you might want to check it twice as frequently....


You can order a printed copy of Q-talk #103 by using the Q-talk Back Issue Order Page.