Normal Operation

Electrical System Normal operation

When entering the cockpit before first flight of the day, there is no electrical supply to the aircraft. All cockpit indications will be off except for the battery voltage indicator and possibly an external power AVAIL light on the electrical panel.

To power the aircraft from batteries, select the two battery push buttons on the overhead electrical panel. This will supply the DC busses. This DC supply allows the cockpit indications to illuminate but not the displays, as they require AC power.

Battery power

When an external power supply is connected to the aircraft, the green AVAIL light is illuminant. This illumination is independent to the aircraft's electrical system. Pressing the external power push button on the overhead electrical panel allows the whole aircraft electrical system to be powered.

External power

APU power

The APU generator may be selected to power the aircraft when the APU AVAIL light is illuminated. If the APU is used to power the aircraft it takes over from EXT B supply, or if only EXT A was powering the aircraft, it takes over the left side electrical power.

Engine generator power

After the engines have been started, the engine generators may be used to power the aircraft. To use the engine generators, press the GEN 1 and GEN 2 push button. Note that these buttons show FAULT at any time that the engine generator is not supplying their AC busses.

Each external power source (A / B ) can supply the whole aircraft but if they are selected together, EXT B normally supplies the left side and EXT A normally supplies the right side.

The left engine drives the GEN 1 which powers the AC 1 bus, from which the AC ESS bus is normally powered.

The right engine drives the GEN 2 which powers the AC 2 bus,

External B powering entire aircraft

External A and APU share powering entire aircraft.