Abstract: An auxiliary power unit is operable to provide bleed air to a vehicle system. A method includes diverting substantially all of the bleed air to an exhaust for a selected time period commencing with startup of the auxiliary power unit. After the selected time period, at least a portion of the bleed air is diverted to the vehicle system.

Abstract: The system and method of the present invention provides stepping speed control of a gas turbine engine to reliably light-off a gas turbine engine. During starting, the speed of the gas turbine engine is incremented by stepped amounts through the light-off window from a minimum speed value to a maximum speed value, with the speed of the gas turbine dwelling at each stepped value for a period of time before incrementing the speed of the engine to the next stepped level. If the gas turbine engine is stepped through the entire light-off window without success, the controller decreases the speed of the gas turbine engine to the minimum value and begins the process again. The process continues until successful light-off is initiated or until the light-off window is traversed a certain number of times, after which the start process is aborted.

Abstract: A turbine controller controls the operation of a gas turbine generator used to drive an electric generator of an aircraft. The turbine controller controls the gas turbine generator according to air flow demand signals indicative of air flow required by an air management system that regulates cabin pressure and temperature of the aircraft.

Abstract: The system and method of the present invention provides stepping speed control of a gas turbine engine to reliably light-off a gas turbine engine. During starting, the speed of the gas turbine engine is incremented by stepped amounts through the light-off window from a minimum speed value to a maximum speed value, with the speed of the gas turbine dwelling at each stepped value for a period of time before incrementing the speed of the engine to the next stepped level. If the gas turbine engine is stepped through the entire light-off window without success, the controller decreases the speed of the gas turbine engine to the minimum value and begins the process again. The process continues until successful light-off is initiated or until the light-off window is traversed a certain number of times, after which the start process is aborted.

Abstract: A system and method of controlling the acceleration of a load driven by a gas turbine engine detects the existence of an overload condition and reduces an acceleration setpoint when such condition arises.

Abstract: In a power transmission or generation apparatus having a source of heated pressurized air, the problem of achieving rapid controlled engagement of a hydraulically actuated clutch at low ambient temperatures is solved by utilizing a portion of that heated pressurized air for heating only that small control volume of hydraulic fluid within a clutch control circuit needed to achieve rapid actuation and stable control of the hydraulic clutch. Our invention is thus particularly applicable in a power transmission or generation apparatus having a gas turbine engine, or a turbocharged piston engine as the prime mover. With gas turbine engine powered units, our invention contemplates the use of compressor discharge air, rather than exhaust products for heating the hydraulic fluid. Similarly, for piston engines our invention contemplates the use of turbocharger discharge air rather than exhaust products.