Aircraft electrical power system including air conditioning system generator

An electrical power system for an aircraft, the electrical power system comprising:

• a first ac generator bus;
• a second ac generator bus;
• a first main engine generator operable to provide variable frequency ac power;
• a second main engine generator operable to provide variable frequency ac power;
• an ACS generator operable to provide variable frequency ac power;
• a plurality of relays;
• and
• a controller and for controlling the relays to connect an output of the ACS generator to one of the ac generator buses while the ac power from the ACS generator is within a frequency range, the controller controlling the relays to connect an output of one of the main engine generators to the other of the ac generator buses.

A method of providing electrical power to an aircraft having an ac generator bus, a main engine generator and an air conditioning system including an ACS generator, the method comprising the steps of:

• operating the air conditioning system, whereby the ACS generator generates ac power having a variable frequency;
• determining whether the variable frequency ac power is within a frequency range;
• supplying the variable frequency ac power to the ac generator bus while the variable frequency ac power is within the frequency range;
• and
• using the main engine generator to provide backup power for the ACS generator when the ac power from the ACS generator is out of specification.