Just in case anyone else has the same problem:
twice on a hot day, after a no problems morning flight, on return my CS prop
wouldn't
come off fully fine or respond at all. Controller etc behaving as expected.
The prop is about 6-8 years old and 325 hours and has been great previously.
I just had to fly old school controlling RPM by throttle and pitch to keep
below max rpm (speed about 80knts).
After investigation of slip rings, wiring, switches etc, I concluded the most
likely
cause was the two connections between the slip ring and switch wiring (blue
and yellow/green), these are under heat shrink and comprise individual nickel
plated screw terminals. I found the body plating to have come off and rusty
and the terminal screw to also be corroded and rusty.
My plane is always in a hangar.
If anyone knows how the circuit works I'd be interested to know (its in the
manual);
I thought I had it worked out but had assumed normally closed switches that
open at the limit but it seems they are normally open closing at the limit
which has me confused (an electronics engineer). Found slight signs of burn on
one contact. I understand the hub/switch arrangement has been changed on the
current design.
Another point to note is that although I had painted the collars at blade route
with 2 part aluminium primer (which had halted some surface corrosion) During
this investigation I saw that I hadn't painted all the way round by the
switches.
this required some further surface treatment. It would be a bad day if the
collar split.
--------
Graeme Bird
G-UMPY - Mono Classic/XS FFW 912S, Woodcomp SR3000/3W CS, trutrak Gemini 2 axis
AP, PAW, PFLARM core, ads-b out, 8.33khz, mode S, FP-5, Aera500, SD on Nexus,
Smart A3
350 hours & 6 years on the Mono, 930 total
g@gdbmk.co.uk
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