(19)
Connect fuel hose to inlet side of filter assembly.
(20)
Restore airplane to normal configuration.
(a)
Position lower shroud against upper shroud and close shroud latches.
CAUTION: MAINTAIN A MINIMUM CLEARANCE OF 0.18 INCH BETWEEN ENGINE PLUMBING, FIRE DETECTOR, CLAMPS AND INSIDE SURFACE OF LOWER SHROUD. EXERCISE EXTREME CARE NOT TO DAMAGE SHROUD DRAIN LINES WHEN HANDLING SHROUD.
(b)
Disengage APU compartment access door support rods and stow rods. Close and latch access door.
(c)
Remove placard from BATTERY switch.
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8. APU Control Air Pressure Line Leak Check (Fig. 203)
A. General
(1) The following procedure permits a quick economical means of checking for leak in control air pressure line.
B. Equipment and Materials
(1)
Compressed air source
(2)
Pressure gage (0-50 psig)
(3)
Standard tee fitting
(4)
Air supply line
(5)
Shutoff valve
C. Prepare for APU Control Pressure Air Line Leak Check
(1)
Position BATTERY switch to OFF and placard.
(2)
Open APU compartment access door latches and open access door. Install door support rods.
(3)
Support shroud, open shroud latches, and remove shroud.
CAUTION: EXERCISE EXTREME CARE NOT TO DAMAGE SHROUD DRAIN LINES WHEN HANDLING SHROUD.
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D. Check APU Control Air Pressure Line Check
(1)
Disconnect compressor discharge pressure line (control air pressure line) from compressor discharge orificed tee. Remove and save compressor discharge orificed tee for installation.
(2)
Connect a standard tee fitting to control air pressure line.
(3)
Connect a pressure gage, air supply line and shutoff valve to tee fitting.
(4)
Plug acceleration limiter valve orificed vent (if installed) on the fuel control unit.
(5)
Connect compressed air source to air supply line.
(6)
Open shutoff valve and apply 40-psig pressure to control air pressure line.
(7)
Close shutoff valve.
(8)
Observe pressure gage.
(a)
Pressure decay should not exceed 3 psi/minute.
(b)
Correct any leaks in the control air pressure line.
(9)
Disconnect compressor air source from air supply line.
(10)
Remove plug from acceleration limiter valve orificed vent (if installed) on the fuel control unit.
(11)
Disconnect a pressure gage, air supply line and shutoff valve from tee fitting.
(12)
Disconnect a standard tee fitting from control air pressure line.
(13)
Connect compressor discharge orificed tee to control air pressure line.
(14)
Restore airplane to normal configuration.
(a) Position lower shroud against upper shroud and close shroud latches.
CAUTION: MAINTAIN A MINIMUM CLEARANCE OF 0.18 INCH BETWEEN ENGINE PLUMBING, FIRE DETECTOR, CLAMPS AND INSIDE SURFACE OF LOWER SHROUD.
EXERCISE EXTREME CARE NOT TO DAMAGE SHROUD DRAIN LINES WHEN HANDLING SHROUD.
(b)
Disengage APU compartment access door support rods and stow rods. Close and latch access door.
(c)
Remove placard from BATTERY switch.
9. Procedure Following Over-temperature During Start
A. General
(1) During start/acceleration cycle, if EGT exceeds Red Line (760°C), the following items must be accomplished to prevent reoccurrence.
B. Prepare for APU Examination
(1)
Position BATTERY switch and APU start switch to OFF and placard that APU maintenance is "in work."
(2)
Open circuit breaker on M280 module APU accessory unit on E3-3 electronic shelf.
(3)
Open APU compartment access door latches and open access door. Install door support rods.
(4)
Support lower shroud, open shroud latches, and remove shroud.
(5)
Remove combustor unit (Ref 49-31-42 R/I).
CAUTION: EXERCISE EXTREME CARE NOT TO DAMAGE SHROUD DRAIN LINES WHEN HANDLING SHROUD.
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C. Examine APU
(1)
Visually examine the hot section for evidence of distress.
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