Abstract :
The auxiliary power unit (APU) is one of the important parts of an aircraft which is located at the tail of the aircraft. APU works as a producer of electricity and pneumatic power (pressurized air) to start the engine and air conditioning when the aircraft is on the ground. Which is the source of air pressure used for the bloody air system. Normally the air pressure indicator will give a designation of 30-40 psi when the APU rotation speed reaches 95%. If there is a failure in the bleed air system, the indicator cannot provide an appointment. This resulted in aircraft that did not get pneumatic supplies from the APU. Failure to indicate the indicator can be caused by a bleed air valve which cannot continue pressure to the aircraft due to signs of corrosion on the valve surface so it cannot open. After knowing the problem do the troubleshooting, according to the procedures of the Aircraft Maintenance Manual ATA Chapter 49 must be replaced with new components