PURGING THE APU FUEL SYSTEM.

TM 55-4920-424-13&P

3-6.

The followin g checks should be made prior to operating the auxiliary power unit.

a. Check plumbing and electrical wiring connections for security of attachment.

CAUTION

Do not operate APU with air inlet screen removed. Ensure operating area is clean

of loose items. The greatest hazard to a gas turbine engine is possible ingestion

of foreign material into the engine compressor.

b. Position stand to allow safe exit of exhaust gas.

c. Check tires for sufficient air pressure (40 to 45 psig).

d. Check fuel tank dipstick for sufficient quantity of fuel (1/4 tank minimum).

CAUTION

Jet thrust of APU may cause stand to move if parking brake is not applied (brake

handle up).

e. Ensure that parking brakes are applied (brake handle up).

f. Check all gages on ins trument panel for zero indication.

g. Check that all switches on instrument panel are in the OFF position, and that circuit breakers are pulled.

h. Check APU oil sump for full quantity of engine lubricating oil according to appropriate TM.

i. Purge APU fuel system. Refer to paragraph 3-7 for purging procedure.

3-7.

PURGING THE APU FUEL SYSTEM.

3-8. The following purging procedure is for the purpose of depreserving, or purging, the APU fuel system when a

preserved or repaired engine is to be operated.

a. Disconnect harness connector from APU ignition exciter input. Insulate connector to prevent accidental contact

NOTE

If desired, fuel lines may be disconnected from fuel solenoid valves rather than

from fuel manifold and start fuel nozzle. Connect suitable drain lines to fuel

solenoid valves, and place open ends of drain lines into a waste fuel container

(one-quart minimum capacity).

E-18 Change 2