To overcome the disadvantages of the computation model for auxiliary power unit (APU) air bleeding performance in engineering

the structure characteristics and working principle of APU with load compressor were researched. A model based on the matching principle between APU and air start turbine and an interpolation model of variable geometry characteristics of load compressor were presented. On this basis

the regulation law based on APU flat rating was researched

and the relationship among the shaft power load

the APU turbine inlet temperature

the exhaust gas temperature and the inlet guide vane angle of load compressor was determined

consequently the APU bleeding performance was computed at various states in flight envelope. The model was validated with GTCP131-9A’s test data. Results showed that

the deviation of air bleeding mass flow was within 3%

while the deviation of air bleeding pressure was within 4%; in addition

the turbine inlet temperature limit at different altitudes was only related to the shaft power load

but not to the inlet temperature. The model provides a good reference for performance simulation and regulating law design of APU with load compressor.