Boeing 777-200 Preflight Inspection Part 1 | APU Start

Boeing 777-200 Preflight Inspection Part 1 | APU Start Prior to each flight of the day a preflight inspection of the plane is required to determine the aircraft readiness to fly. During the preflight inspection the aircraft systems are tested and visual inspections are conducted. During this part I arrive on the plane to power up the APU and begin the preflight. First thing I do is to go to the EE (electronic equipment) bay to connect the main battery. We disconnect the main battery during parking to prevent it from discharging. After the battery is connected I start the APU to provide electrical power and pneumatic pressure. As the APU reaches 100% rpm the APU generator automatically comes online and begins to supply electricity to the aircraft. When the aircraft receives electric power the avionics systems power on and begin to run their BITE (built in test equipment) to verify that they are operating normally. If there is a fault detected during the BITE then it will be displayed for me to see and I can determine what corrective action may be required.