OPERATION OF THE APU.

TM 55-4920-424-13&P

(3) Maintain adjustments of (1) and (2) preceding throughout all testing of the engine on test stand.

CAUTION

To avoid high exhaust gas temperature, do not operate APU on test stand with

acceleration schedule adjustment lever in mid-position of adjustment slot.

(4) Upon completion of testing, prior to removing APU from test stand, move acceleration schedule adjustment

lever to mid-position of adjustment slot.

3-11. OPERATION OF THE APU.

WARNING

Operation of this equipment presents a noise hazard to personnel in the area. The

noise level exceeds the allowable limits for unprotected personnel; wear ear muffs

or earplugs which were fitted by a trained professional.

3-12. Starting. (See figure 1-4.)

a. Place instrument panel switches in the following positions:

(1) START-ON-OFF switch to OFF.

(2) DC GEN ON-OFF/RESET switch to OFF.

(3) AC GEN ON- OFF-TEST switch to OFF.

(4) AC selector switch to any marked position.

b. Push in TURBINE CONTROLS circuit breaker.

c. Push in DC GEN CONTROLS circuit breaker.

d. Move START-ON-OFF switch from OFF to ON.

(1) Fuel boost pump starts.

(2) HIGH EXHAUST TEMP, OVERSPEED, and LOW OIL PRESSURE indicator lights illuminate.

e. Press to test all remaining indicator lights at this time, if desired.

f. Move RESET switch to RESET, then release. 90% SEQ CHECK light illuminates.

g. Move START-ON-OFF switch from ON to START, then release.

Note

HIGH EXH TEMP, LOW OIL PRESSURE and OVER-SPEED lights extinguish as APU

accelerates. At 90 percent speed, the 90% SEQ CHECK light extinguishes.

3-7