(a)
Turbine wheel tips for erosion/burning.
(b)
Turbine wheel blades for erosion/rubbing.
(c)
Nozzle guide vanes and torus for erosion.
(2)
If examination indicates no evidence of distress, accomplish steps in par. D and E and return APU to service.
(3)
If examination does indicated distress, the APU must be removed (Ref 49-11-0) for Hot Section Inspection (HSI) and necessary maintenance action.
NOTE: Instructions for performing HSI are outlined in Heavy Maintenance section of the APU Engine Overhaul Manual, 49-20-31.
D. Recondition APU
(1)
Replace combustor unit with a replacement unit (Ref 49-31-42 R/I).
(2)
Replace fuel control unit (Ref 49-31-11 R/I).
(3)
Replace control thermostat (Ref 49-52-32 R/I).
(4)
Check fuel drains for freedom from obstruction (Ref 49-12-0 C/P; 49-31-71 I/C).
(5)
Check airplane battery voltage (22 volts dc minimum).
(6)
Close circuit breaker on M280 module APU accessory unit on E3-3 electronic shelf.
(7)
Test APU (Ref 49-11-0 A/T).
E. Restore Airplane to Normal Configuration
(1) 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.
(2) Disengage APU compartment access door support rods and stow rods. Close and latch access door.
10. Procedure to Remove and Install Tachometer Generator
A. General
(1) The tachometer generator should be installed on the APU whenever trouble-shooting situations could be facilitated. The RPM indicator should be used in conjunction with EGT indicator, frequency meter and duct pressure indicator (Fig. 201).
518
49-11-0 Page 216 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Feb 20/88
B. Equipment and Materials
(1) RPM Indicator and Tachometer-Generator Test Set - F72891-20
C. Install test tachometer generator on APU as follows:
(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.
(4)
Connect RPM indicator to tachometer generator.
(5)
Remove placard from BATTERY switch.
D. Start APU per par. 2.B. and 2.C.
E. Observe RPM indicator.
F. Stop APU per par. 2.D.
G. Return airplane to normal configuration.
(1)
Placard BATTERY switch.
(2)
Disconnect indicator from tachometer generator.
(3)
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.
(4)
Disengage APU compartment access door support rods and stow rods. Close and latch access door.
(5)
Remove placard from BATTERY switch.
540
Aug 15/80 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 49-11-0 Page 217
APU Control Air Pressure Line Leak Check 574
49-11-0Page 218 Figure 203 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Nov 15/80
11. Bleeding The Timed Acceleration Fuel Control Unit (TAFCU)
A. General
(1) Some APUs use a TAFCU, when installing a new TAFCU the preservation oil needs to be bled from the unit.
B. Equipment and Materials
(1) Container - 2-gallon minimum capacity
C. Prepare to motor APU.
(1)
Provide airplane with external power.
(2)
Position BATTERY SWITCH to OFF and placard.
(3)
Open APU compartment access door latches and open access door. Install door support rods.
(4)
Support shroud, open shroud latches and remove shroud.
CAUTION: EXERCISE EXTREME CARE NOT TO DAMAGE SHROUD DRAIN LINES WHEN HANDLING SHROUD.
(5)
Disconnect ignition unit power supply electrical connector from ignition unit.
(6)
Place container under the TAFCU.
(7)
If TAFCU does not have priming valve, loosen the retaining plug one turn.
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