Re post #4 the L1011 APU by Hamilton Standard was based on a PT6. The only good thing about it was it was easy to replace!! I recall replacing one on a 2 hour turnaround at main base when it was difficult to get the airplane rescheduled to overnight at base. One of the best things about the 744 compared to earlier 747 models was the new APU which was vastly superior to the original Airesearch unit.