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4.  Drains (Fig. 1)
A.  The APU drains provide means for draining unburned fuel from the engine and for draining fuel and/or oil from the shroud in event of fuel or oil leakage inside the shroud. At the aft end of shroud, a drain cup with stand pipe picks up unburned fuel discharged through the turbine exhaust port. Two fuel drain lines are manifolded into a fitting on engine. This fitting mates with a drain cup in the drain line. The drain line terminates at a fitting at the forward end of the shroud. Adjacent to the drain line terminal end fitting is another fitting. Through this fitting fuel or oil is drained from the shroud. Both fittings at the forward end of the shroud mate with drain cups in APU compartment access door. The drain cups in access door are connected to a drain mast. For description of the APU compartment access door, refer to Chapter 52.
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APU SHROUD DRAINS - CLEANING/PAINTING
1. General
A.  The APU shroud drain system includes drain cups and plumbing of the lower shroud and the mating seal plates and drain mast of the APU access door.
B.  For additional information regarding drain fittings mating with the shroud drains, see 49-31-71, Fuel Drains - Inspection/Check.
2.  Equipment and Materials
A.  Cleaning solvent - Federal specification P-D-680, or equivalent
B.  Compressed air source - 90 to 100 psi
3.  Clean APU Shroud Drains (Fig. 701)
A.  Open circuit breaker on M280 module-APU accessory unit on E3-3 electronic shelf.
B.  Position BATTERY SWITCH and APU START SWITCH to OFF and placard that APU is “in work.”
C.  Open APU compartment access door latches and open door. Install door support rods.
D.  Support lower shroud, open shroud latches, and remove shroud.
CAUTION:  EXERCISE EXTREME CARE NOT TO DAMAGE SHROUD DRAIN LINES WHEN HANDLING SHROUD.
E.  Using air source, blow through exhaust duct drain tube, aft drain cup and forward drain cup. Ascertain that air flows from through-shroud fitting of forward drain cup.
NOTE:  Forward drain cup can be cleaned by removing cover, blowing cup out with compressed air and reinstalling cover.
F.  Check interior of drain cups for evidence of deterioration due to corrosion.
G.  Blow air through shroud drain fitting. Ensure fitting is clear.
NOTE:  If oil has accumulated in lower shroud, wipe down with solvent. Dry with compressed air.
H.  With APU access door open, blow air through seal plate fittings. Verify that air exits through APU drain mast.
I.  Blow air through two drain holes in forward end of door.
NOTE: If oil has accumulated in door, wipe down with solvent. Dry with compressed air.
J.  Wipe drain mast and external surface of APU access door clean.
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UPPER SHROUD - REMOVAL/INSTALLATION
1.  Prepare Upper Shroud for Removal
A.  Position stabilizer trim in full up position (airplane nose down).
B.  Open stabilizer trim control circuit breaker on P6 panel and placard that APU maintenance is "in work."
C.  Position BATTERY switch and APU master switch to OFF and placard that APU maintenance is "in work."
D.  Open the circuit breaker on M280 module-APU control unit on E3-3 electronic shelf.
E.  Open APU compartment access door latches and open door. Install door support rods.
F.  Support lower shroud, open shroud latches, and remove shroud.
CAUTION:  EXERCISE EXTREME CARE NOT TO DAMAGE SHROUD DRAIN LINES WHEN HANDLING SHROUD.
G.  Remove APU (AMM 49-11-0/401).
2.  Remove Upper Shroud (Fig. 401)
A.  Gain access to horizontal stabilizer jackscrew compartment just aft of pressurized bulkhead.
B.  Reaching through opening in horizontal web, disconnect air pressure line from cooling air shutoff valve pneumatic actuator.
C.  In APU compartment, disconnect generator, starter motor, and APU harness receptacles from fittings in upper shroud.
D.  Disconnect EGT receptacle from fitting in upper shroud.
E.  Disconnect generator control receptacle from fitting in upper shroud.
　
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