Patent ID: 7117683

Claim:
A main engine electrical start system for a gas turbine propulsion engine in an aircraft that has a gas turbine engine powered auxiliary power unit (APU), comprising: a battery for supplying direct current (DC) electrical power; a DC to alternating current (AC) power converter for converting at least some of the DC power from the battery to AC power of desired frequency for an independent electrical power grid; a first dynamoelectric machine coupled to the APU for starting the engine of the APU from AC power supplied by the power converter; a second dynamoelectric machine of the induction type coupled to the APU that generates AC power at the frequency of the independent electrical power grid when the second dynamoelectric machine receives AC excitation current from the power grid generated by the DC to AC power converter; and a third dynamoelectric machine of the induction type coupled to the propulsion engine that starts the propulsion engine when the third dynamoelectric machine receives AC excitation current from the independent electrical power grid generated by the DC to AC power converter and AC power generated by the second dynamoelectric machine.