Re: Turbopro near-instantaneous power (Waterbombers)

From:         Simon Ellwood <Simon@cv990.demon.co.uk>
Organization: Bodge It & Co. Ltd.
Date:         27 Jun 96 12:56:57 
References:   1 2 3 4 5 6 7
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>On a turboprop, like the C-130, the engine spins at approximately 13000
>RPM while the prop spins at approximately 1100. When the pilot advances
>the power, the angle of the prop blades to the airstream change to and
>essentially add lift in the forward direction. The engine as the prop
>pulls more power, it signals the fuel system to increase the fuel, thus
>the power to substain the 1100 RPM and additional thrust.  The near
>instantaneous transition from low thust to high thrust is made possible
>by the torque generated by the turbines spinning at 13000 RPM.  In other
>words, the turbines act as a flywheel, storing energy.
>

I've just caught the tail end of this thread here, but what you seem to
be describing is the operation of a turboprop/constant speed prop unit.

You imply here that advancing the power directly alters the prop blade
angle and then the engine compenasates for the momentary speed loss by
increasing it's power output and restoring the speed. This is in fact
the wrong way round. When the pilot "advances the power", he does just
that - increases the engine power. The engine tries to speed up but the
Constant Speed Unit (CSU) on the prop senses the speed change and
increases the pitch of the prop to maintain the correct engine/prop
speeds.

Simon Ellwood.