Opinions on alternator fault

[Raistlin]

Hi everyone, first post so first of all a quick self introduction: I'm the brand new owner of a Bravo (G1000 equipped, dual alternator, one of the last built). I thank you all for your posts, they have been invaluable through deciding to buy a Mooney and to prepare myself for the transition.

I wanted to pick your collective brain on the only (really) negative experience so far with my new plane. I bought her fresh out of annual (at ACG in Germany), during which the alternators where removed for a 500-hr inspection (total time of everything on board is ~1000 hrs). They were shipped to Vliegwerk Holland BV and back.

Exactly 2 hours of flight later, I had a left alt indication (but the alternator was still charging the battery, at least initially). Shortly afterwards, the left alternator stopped charging the battery at all, and upon inspection on landing we noticed the belt being not tense. Removing the cowling, we found that the pulley on the left alt had come loose, damaging the shaft.

The analysis was that probably the torque on its nut/bearing was not correct, and so in flight it had worked for a little while, while vibrations damaged it. The alternator was deemed not repairable and had to be replaced. I count myself lucky that the pulley did not come detached and bounced around at high speed near the prop and the front of the engine, where it could have caused way more damage...

(I apologize in advance for the terminology, the combination of me being the wrong type of engineer and English not being my native language probably made a mess of it)

The correlation between the inspection and the breakage is, to put it mildly, suspicious to me. However, the shop (Vliegwerk Holland, I mean) maintains that they did not remove the pulley and its nut at all, so they cannot be responsible. Nor, apparently, they checked the torque or the conditions of the shaft.

I don't know if anyone has any past experience of similar faults, or any informed opinions to share.

And while I'm at it... merry Christmas everyone!

[Fritz1]

Welcome aboard, sorry this happened to you, glad you walked away. The question is whether removing and re-torquing the pulleys is part of an alternator overhaul. Sounds to me like at least one pulley was removed and not torqued correctly. Moving forward you will learn who you cant trust and form relationships with the people you trust. Typically it takes 3 types of guys to keep a Bravo going, an engine guy, an airframe guy and an avionics guy. Assisting in maintenance and annuals typically improves the outcome as long as you do not cut into anybody's profits. Trust, but verify, being there in person increases mind share. The Bravo needs 25 oil changes, lubing the waste gate shaft with mouse milk goes with the oil change. Each time look at the turbo transition, that is the big Y in the exhaust, and check for cracks from behind with a mirror. The exhaust is the weakest spot of the Bravo engine. The better you understand your airplane the more reliable it will become and the better the relations with your shops and vendors. Fly safe!