AFI 11-2C-130v3 - BITS

AFI11-2C-130V3 23 APRIL 2012 181
12.10.3.16. APU Fails to Rotate (Start Light Illuminates)
12.10.3.16.1. Remove all electrical power from aircraft.
12.10.3.16.2. Open pilot‘s side circuit breaker panel.
12.10.3.16.3. Check APU current limiter, if bad or suspect, replace as follows. (see
Figure 12.2)
12.10.3.16.3.1. Disconnect the aircraft battery.
12.10.3.16.3.2. Remove and replace the current limiter with available spare.
12.10.3.16.3.3. If no spares are available, open the copilot‘s upper circuit breaker
panel and remove the cargo winch current limiter and use as a replacement for the
APU current limiter.
12.10.3.16.3.4. If the current limiter is good, check APU starter (see Figure 12.6)
for broken wires and repair as necessary.
12.10.3.16.3.5. Connect the aircraft battery and attempt another start. If no
rotation is noted, ―tap‖ the start relay.
12.10.3.16.3.6. If APU still will not rotate, place the APU control switch to
START momentarily, and then release the switch to RUN. Place a #4 jumper
wire between post A-1 and post A-2 of the APU start relay until the start light
goes out, then remove the jumper wire.
12.10.3.17. APU Rotates – Negative Ignition – No Ignition Noise
12.10.3.17.1. Swap the Fuel Holding Relay (FHR) with the Auto Start Relay (ASR)
(see Figure 12.6).
12.10.3.17.2. Attempt to start APU.
12.10.3.17.3. If APU fails to start – Remove oil pressure switch cannon plug and
place a jumper wire from pins ―A‖ to ―B‖ (ignition) and another jumper wire from
pins ―C‖ to ―E‖ (fuel). Secure with tape. CAUTION: Prior to jumping oil pressure
switch, ensure oil pressure line from the pressure switch and motor the APU. Oil
should spurt from the line if the pump is working.
12.10.3.17.4. Attempt to start the APU.
12.10.3.17.5. If APU does not start, the igniter, exciter, or ignition harness may be
faulty.
12.10.3.18. APU Rotates – Negative Ignition – With Ignition Noise
12.10.3.18.1. Manually open the APU motor operated fuel shutoff valve as follows:
NOTE: APU shutoff valve is located in the aft outboard corner of the number two
dry bay (tag ID ―O‖).
12.10.3.18.1.1. Ensure the APU Control switch is in the ―OFF‖ position.
12.10.3.18.1.2. Pull the APU Control circuit breaker on the isolated DC bus.
12.10.3.18.1.3. Remove the number 2 dry bay access panel.