Safety Investigation Report 2018:1 Factual Information/1.6/1.6.8 Aircraft Systems/14
SAFETY INVESTIGATION REPORT MH370 (9M-MRO)
14) Auxiliary Power Unit
The aircraft is fitted with an Auxiliary Power Unit (APU) - Model: GTCP 331-500 - manufactured by Allied Signal. The Allied Signal GTCP 331-500 gas turbine APU is a two-stage centrifugal flow compressor, a reverse flow annular combustion chamber and a three-stage axial flow turbine. It supplies the auxiliary power system for the aircraft pneumatic and electrical power. This permits independent operations from the ground external power sources or the main engines.
The APU generator supplies 120 KVA electrical power at any altitude. The APU can start at all altitudes up to the service ceiling of the aircraft (43,100 ft/13,100 m). Electrical power is available up to the service ceiling and pneumatic power is available up to 22,000 ft (6,700 m).
The ELMS contains the APU autostart logic and sends signal to the APU Controller (APUC).
The APU Controller serves to control the APU functions for:
- Starting and ignition
- Fuel metering
- Surge control
- Inlet guide vane (IGV) control
- Data storage
- Protective shutdown
- BITE/Fault reporting
- APU indication
The APU is designed to automatically start when certain logic conditions are met when the aircraft is in the air or electrical power removed from left and right transfer buses from respective No. 1 and No. 2 engine generators.