ORIGINAL: Gaspar

Hello Paul,

Some friends have mailed me pointing to this thread.

Please STOP your tries in to accuse the Ecu of the problems of the engine.

Don't try to confuse the readers pointing to something outside the engine. It is clear that something failed, I have my own theory from the reports from first hand witness, but I leave to PH this. About your theory:

1. If ecu fails to disengage the starter: Ecus aren't God, they only can cut the supply to the starter. The only weird thing that the ecu can do is not stop the starter, very unlikely as the ecu short circuit the starter to brake it, but anyway, once the rotor rpm is higher than the starter RPM (say 30.000RPM for a Speed300 motor) the bendix disengages itself automatically. It is a mechanical thing, when the torque goes inverse, the bendix retracts, nothing to do with the ecu.
If the bendix keep stuck (mechanical problem, it is a part of the engine, not from ecu) the only think that happen is that the torque of the engine at low RPM (say 30.000) can't drive the starter motor with its terminals shortcircuited from the ecu. Again, the torque is high and inverse, the bendix should disengage, if not, the RPM fall and some fire exit from the exhaust. No way to arrive to idle.

Supposing that the engine can arrive to idle with the starter engaged....that is a lot of supposition... Let me know what starter you use that can survive 4 minutes at 150Krpm. And the ecu should have survived 4 minutes at 50V of back EMF... that's reliability! Not many appliances allow a voltage 7 times higher than nominal...

And the suposition that a starter shaft (a fault outside the engine, again [&o] ) with his tiny 2mm of diameter can upset the preload and damage the bearings is ridiculous, sorry. No way that it can hold full 4 minutes and do enough force to upset the preload... and this force should be against the engine, just inversely as the sense of the bendix...

Why the starter and ecu are fried? Simple. As soon as the engine begin to fail (yes, the engine failed first) (say blades lost, say bearing, say the pilot doing a loop at +40g, say whatever you want) the shaft begin to run eccentric. As the compressor nut sit inside the bendix with a small clearance, this eccentricity made that the compressor nut contacted to the bendix, driving the starter at full RPM. The ecu keept the starter shortcircuited, but the instant power was too high for it and fried both, ecu and starter. This was just after the bearing fail, and during the time that the engine run until stop. Also, any tries to cooldown the engine trough the ecu withn the starter fried could have damaged the ecu too.

Later,

Gaspar