767 APU Hung Start

 767 APU Hanging at 30% During Start

During the APU engine start, the IGV (Inlet Guide Vanes) are supposed to be closed. This allows all incoming air to be directed into the combustion chamber. After start with a air demand (main engine start or air conditioning pack operation), the IGV vanes open allowing bleed air output.

We purposely pulled the IGV actuator arm out (vanes open) to see if it would would close them on initial rotation. It did not.

With the drain on the air bleed system, the APU could not accelerate beyond approximately 30% and it would shut down.

More troubleshooting here.