IMPORTANT - calling ex-Dowty Propellor personnel
Wanted - anyone with experience or knowledge of Dowty hydraulic constant-speed propellors, as fitted to Rolls Royce Dart engines.
In our historic aircraft collection at Speke aerodrome, we have 2 of the above propellors. We gather that these propellors use a combination of hydraulic fluid and very powerful springs to control the pitch whilst running, with the springs set to return the propellor to a feathered position which is its inert or "safe" position.
Both of our props carry stern warnings that the propellor MUST be feathered before removal from the aircraft for this reason. Unfortunately, one of them was removed whilst it was still set in a windmilling position, god knows why. However, what we understand is that this means we now have an armed and dangerous propellor sitting in a stand in our storage area with the springs under tension, that could potentially snap back to feathered position with incredible force at the slightest provocation. For this reason, nobody dares touch it and we have no idea how to go about making it safe to a) be in the vicinity of when fetching other parts and b) to reinstall on the aircraft.
I had suggested tapping the blades with a mallet at arms length to make it go, but this was vetoed as no one is quite sure how it would react, and if letting it go by itself would cause damage to the hub and pitch mechanism.
We are desperately after someone who either designed or worked on these units to please advise us on how to disarm the mechanism (or if it is indeed possible to do so without having to reconnect a hydraulic supply?).