Interesting. I was thinking a free-wheeling diode might help the situation,
but in order do it, you'd need a true isolator-type diode arrangement. That would
require a diode in the starter motor path... not too great of an idea (WAY too much
current to be reasonable/reliable). The separate contactor for the solenoid would
probably work fine, but the FAA goons are already circling on that one. It's not a
PMA'd replacement if you need to install additional stuff on the airframe. Then it's
an STC and would require more certification and paperwork, etc.

The more I think about it, the more I realize that it was probably a necessary
compromise. Even if you put the contactor *ON* the starter for just the solenoid,
there's no way for it to "know" that the voltage on the starter motor lug is from the
battery vs. the back EMF in the motor. I suppose you could measure the motor current
with a shunt (haha!) or winding, but again... it's more complicated and failure-prone.
The system they have is safe and simple, if a bit inelegant. I doubt the starter gear
could damage the ring gear much since there's no load on it at the time. All it's
doing is free-wheeling the sprag clutch. I suppose it would be good to keep the RPMs
as low as possible until it stops (but then again I do that anyway while the oil
pressure comes up).

Interesting... I think it might even be worth it for the 10 lb weight savings, though.

-Cory


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* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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