RPM & Torque
rudderrudderrat, the Allison T56 is essentially a constant speed engine/gearbox/propeller installation with propeller blade angle selectable only in the 'ground' range of throttle lever travel (except feathering or unfeathering of course). Once in the 'flight' range (flight idle to 90 degrees throttle angle) the throttle simply schedules fuel flow and the propeller is governed to 100% RPM (1021 RPM) + or - 2% in basic hydraulic governing mode. The obvious advantage in having such an engine is almost instantaneous response to throttle movement (limited to not moving the throttle from Flight Idle to Max in less than 1 second) Without getting the purists throwing stones the torque value indicated on the C130 is the load imposed on the engine torque shaft ( and thus the engine itself) by the reduction gearbox, accessories and propeller. This whole thread seems to have become the site for "ego boosting" by some, surely not what the original poster was looking for. I am sure you, barit1 and I each would understand that as a crew member our concern would be "Have I got the torque or power I expect within the RPM and T.I.T limitations applicable and, if not, why not?" I am familiar with the use of N1 and EPR (or IEPR on the RB211 engine) as a measure of thrust. Whether we call the motive force Horespower, Thrust, Torque or any other name doesn't really matter. Every aircraft I have operated has had a specific set of parameters which are to be met before and during flight.
Last edited by Old Fella; 1st Apr 2012 at 11:11.