josok wrote:
>
> Just to bury the 3rd ring-reverse power nonsense once and for all: If
> there would have been power on the 3rd ring, the controller, which
> also was engaged would have tried to increase pitch. Which would have
> caused a full short circuit. With the result that the cb would have
> cut in at the very same moment. The pitch would have been reduced,
> minimally, and i still would have had a very flyable airplane.
Unless, of course, a relay, powered by the reverse circuitry,
automatically switched mode as well. ;-)
I can't see what could have happened without a diagram. The 3rd ring
reverse power thing is so far the most reasonable explanation, for the
other things (like failed micro-switches, failed diodes, and more of
that good stuff) you still have the problem that something was putting
out power to the prop, while the RPM was already way above the target
value. True that a failed micro switch or diode can allow this to
happen, but they can not cause this to happen, they can not put power on
the system by themselves, unless something is putting out power to them.
In the scenario of failed switches you also have to bring in a failed
controller at the same time, still providing power while the prop was
already over the limit. You can't get rid of this multiple-failure
scenario, and that is, like we all know, a scenario which is the least
unlikely. At least, this would imply that Smart Avionics is as "guilty"
as Woodcomp, and failed at the same time as the micro-switches. I
haven't heard you about Smart Avionics yet.
About the lack of mechanical endstops, someone has sent pictures of the
inside of the Woodcomp propeller, with the mechanical endstops clearly
visible.
But true, if the prop has to be able to go to reverse, you can't have
the endstops.
You'd better warn people not to install reverse systems.
Look here, I can understand that this is a sensitive topic for you. But
I guess the reason of this discussion is and remains to find out whether
the failure occured can happen to anyone because it is a design flaw, or
that it most likely happend by a combination (perhaps) of a failure in a
home brew safety bypass system and the fact that the propeller system
was able to go to fine pitch anyway because of the reverse option.
With other words: without reverse, Woodcomp's are safe propellers.
--
Frans Veldman
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