HIGH EXH TEMP and OVERSPEED lamps extinguish.
As APU accelerates to 90 percent speed, the UNDER-
SPEED lamp should extinguish.
If the APU does not light off because of entrapped air in
the APU fuel system, loosen the electrical connector
from the fuel pressure switch; but keep the connector
engaged. Crank the APU and dieconnect the pressure
switch connector. As soon as the APU lights off, recon-
nect the connector, and tighten securely.
Observe that the APU accelerates smoothly to rated speed as indicated on the
Exhaust duct and silencer are hot during operation. Keep
clear of combustibles. Operation of the APU without the
combustor blankets will also expose hot surfaces. Avoid
physical contact to preclude personal injury.
Close the exhaust silencer bypass door after the APU reaches operating speed.
When the APU reaches operating speed, press VOLTAGE REG circuit breaker
to put the dc generator on the line. The dc generator will then furnish power
to charge the battery, run the fuel boost pump, and energize the APU control
relays. Do not overcharge the battery. Refer to TM-11-6140-205-12 for
If the EXHAUST TEMP indicator indicates abnormally high (or low) tempera-
tures during starting, adjust the APU fuel control unit. Refer to paragraph 3-10
for the fuel control adjustment procedure.
A high temperature and a faster-than-normal start indicates
a rich fuel schedule.