Description (AMM 49-00-00)

 

A- The APU controls have switches that are automatically and manually controlled. These switches start, operate, and stop the APU engine. The components for the APU controls are found on the APU engine, in the APU control unit, and on the P5 forward overhead panel.

 

B- The main components of the APU controls are the APU master switch and APU control unit.

 

The airborne auxiliary power for the airplane is supplied by a gas turbine auxiliary power unit. The APU can supply pneumatic bleed air and electrical power to the airplane while the airplane is on the ground or in flight. The APU operation is controlled by the APU control unit.  B. The APU has a gas turbine engine, APU electrical generator and electronic controls. The APU engine turns the APU electrical generator through the gearbox assembly. The electronic controls make sure that the APU operates safely and continuously. The airplane pneumatic system connects to the APU bleed system. The APU electrical generator supplies the electrical power to the airplane electrical system. The APU has a fire protection system. C. The APU is found in a compartment in the airplane tail section. To get to the APU, the APU cowl door must be opened and the lower shroud must be removed. D. The No. 1 fuel tank supplies the fuel for the APU operation. The airplane battery supplies the electrical power for the APU. To start the APU operation, the APU master switch is moved to the START position and released to the ON position. The APU fuel valve and the air inlet door open. The fuel, ignition, and acceleration are controlled to permit the APU engine to operate safely and quickly. When the APU speed gets to 100%, pneumatic power and electrical power are available for the airplane operation.