A bit rusty on the 744 I believe the valve closes to help prevent an auto shutdown so I guess as soon as the signal from the eng start lever is received and the APU begins its ramp up for the 40psi that it's meant to deliver something happens and the valve is commanded closed to protect the APU from an auto shutdown. Any new CMC message after the torque motor replacement? Maybe the IGV's aren't moving as required?
Last edited by CCA; 5th Aug 2018 at 05:05.