An auxiliary power unit (APU) provides electrical power and pneumatic supply for aircraft air conditioning and main engine start. If an APU malfunctions at the gate, consequences could be severe. For this reason, it is essential to ensure APU maintenance is kept up on.
INDICATION OF APU MALFUNCTION
Sometimes, the only indication of APU malfunction is when there is loss in bleed pressure and an increase in exhaust gas temperature. These indications are likely to occur after lengthy aircraft operation in extremely hot environments. These conditions require additional fuel to be used by the APU. When additional fuel is needed, the chance of hot section distress is high. When an APU is stripped down it is not uncommon to see degradation present in the compressor sections. Substantial degradation will likely be present within the hot section of the aircraft engine.
One of the first steps of APU maintenance induction is look into the level of repair required. This can be determined by carrying out a borescope inspection. After inspection, MRO providers can then carry out preliminary testing on the engine. Notably, testing of the engine should be avoid if the borescope displayed hot section damage or excessive oil leakage.
By performing regular APU preventative maintenance, expensive overhauls can be avoided. Proper maintenance needs to be performed; therefore, it is important to ensure that your maintenance provider is doing extensive APU checks and repair. Often times, APU maintenance is kept to a minimum and overlooked. When this happens, chances of costly repairs and overhauls are likely. To avoid these repercussions, proper maintenance and trend monitoring programs should be utilized.