Russell Kent wrote:

Mark Wrathall asked:

How long do you think before people get seduced by the idea of a constant
speeding prop, and build a cheap electronic governer to drive pitch changes into
this system? If you programmed enough hysteresis into the controller, the
solenoid system should be fine, but if the prop tries to hold perfect set rpm,
it wouldn't last long.

Paul Lamar responded:

I don't know Mark but if they insist they will have to put up with the same
brush life as a Hoffman or MT electric prop.

I disagree.  I think it would be a matter of setting customer expectations: the
electronic controller would only adjust the prop pitch when the RPM setpoint was
more than some small number of RPMs away (10, 15, 25).  Then engage the solenoid
and adjust to exactly the RPM setpoint (+/- 2 RPMs, say).  Further, the brushes
would need to remain engaged for a short period of time thereafter (perhaps 60
seconds).

During climb & descent: the system engages and remains engaged due to constantly
changing throttle position or altitude (combined with 60 second "stay on" timer).
During cruise: the system engages rarely (if at all) once cruise altitude and
throttle position are reached.

This would probably be more wear&tear than the "pilot controlled RPM" as the
system is designed today, but it would be nowhere near as much wear as a
continuously engaged brush system like Hoffman or MT.

So tell the customer it will maintain prop RPM +/- 25 (or whatever the "small
number of RPMs" is set to), rather than the +/- 2 RPMs that Hoffman or MT are
capable of.  The performance difference seems negligible, while the wear&tear
difference seems significant.  Of course, one would need to make certain the
solenoids were rated for such a duty cycle.

Russell Kent

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