PRELIMINARY CHECKS.

TM 55-4920-424-13&P

(4) Remove thermocouple (7) from its stowage bracket on check stand, and connect it to thermocouple boss

on top of combustor exhaust outlet. Tighten thermocouple securely.

CAUTION

Do not transport mobile check stand over rough terrain with APU installed.

Vibrations and shock may damage vital APU parts.

3-5.

PRELIMINARY CHECKS.

3-6.

The following 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. Direct 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.

e. Check speed increaser oil sight glass for full quantity of lubricating oil.

CAUTION

Jet thrust of APU may roll stand if parking brake is not applied (brake handle up).

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

g. Check all gages on instrument panel for zero indication.

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

i. Check APU oil sump for full quantity of engine lubricating oil (3 U. S. quarts).

j. 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.

3-3