In a conventional reciprocating piston, internal combustion engine, torque is near zero at low engine output speed and peaks somewhere in the middle of the engine operating range and then decreases as output speed further increases. On the other hand, a gas turbine engine has very high torque at low engine speeds.
To provide a friction start clutch in a transmission for a high torque engine, such as a gas turbine engine, one would need a very wide range of torque capacity, and thus, a very high capacity clutch. A single large clutch piston would require a clutch piston apply area having sensitivity at a high level. If 100 psi were necessary to apply the clutch, a 1.0 psi variation in pressure would result in a large torque variation which would be objectionable at light throttle starts. Such an adjustment to provide adequate clutch apply pressure would not provide a controllable sensitivity.
The present invention provides a novel clutch arrangement and control strategy for transmission starting in a high torque engine.