(2)
Push the IGV mechanism manually back to the CLOSED position.
(3)
Engage the axial-scale measuring device through the ring of the quick-disconnect pin.
(4)
Put the quick-disconnect pin back to the clevis of the IGV rod.
(5)
Measure the load necessary to pull the IGV mechanism back to the OPEN position. Make sure that the maximum load is not more than 9.8 daN (22.0312 lbf).
(a)
If the measured load is lower than the maximum load:
-IGV mechanism is serviceable.
(b)
If the measured load is higher than the maximum load:
-remove the APU (Ref. TASK 49-11-11-000-003).
(6)
Install the IGV Actuator (Ref. TASK 49-23-51-400-003).
5. Close-up
________ Subtask 49-23-51-410-053
A. Close Access
(1)
Make sure that the work area is clean and clear of tool(s) and other items.
(2)
Set the LIGHT control switch 11LJ to the off position.
(3)
Close the APU access doors 315AL, 316AR (Ref. TASK 52-41-00-410-001). Subtask 49-23-51-860-056
B.
Aircraft Maintenance Configuration
(1)
Remove the access platform(s).
(2)
Remove the warning notice(s).
(3)
Make sure that this(these) circuit breaker(s) is(are) closed: 1KD, 2KD.
ACCESSORY DRIVE GEARBOX - DESCRIPTION AND OPERATION
___________________________________________________
R **ON A/C 001-003, 051-099, 401-499,
1. General
_______ The cast-aluminum accessory-drive gearbox (referred to as the gearbox) supplies the drive pads for the Auxiliary Power Unit (APU) generator and accessories which include:
-
the starter motor assembly,
-
the oil pump assembly,
-
the fuel control unit (FCU),
-
the cooling-air fan assembly.
2. Component Location
__________________
(Ref. Fig. 001)
-------------------------------------------------------------------------------FIN | FUNCTIONAL DESIGNATION | PANEL|ZONE|ACCESS | ATA | | | | DOOR | REF. -------------------------------------------------------------------------------VALVE REGULATING GEARBOX 315 315AL 49-26-53
3. Description
___________ (Ref. Fig. 001) The accessory drive gearbox is a module. You can remove it complete from the APU, which lets all the gears, bearings and seals remain in position. The gearbox is of a low drag design with less weight, improved gear lubrication and cold start reliability.
A flanged joint attaches the gearbox to the load compressor. The APU gives a direct drive to the gearbox. The APU forward side mounts are part of the gearbox structure, which is also an oil reservoir (for the wet-sump lubrication system) (Ref. 49-90-00). The capacity of the oil reservoir is
6.1 l (1.6 US gal). The gravity fill port is part of the gearbox housing. A direct-reading sight glass, installed adjacent to the gravity fill port, gives a visible oil-level indication. An oil level switch, installed in the sump, gives minimum oil-level indication signals to the Electronic Control Box (ECB) 59KD (Ref. 49-93-00).
The gearbox regulating valve controls the release of the air pressure in the gearbox in relation to the ambient air pressure. The air provides a positive pressure which helps to prevent oil foaming. The air pressure is released to the APU exhaust through the air/oil separator and vent lines. In higher altitude, the gearbox regulating valve closes and the air pressure in the gearbox cannot release.
Accessory Drive Gearbox
Figure 001 (SHEET 1)
CES
Accessory Drive Gearbox
Figure 001 (SHEET 2)
CES 4. Operation
_________ (Ref. Fig. 002) Pressurizing air enters the gearbox during operation from the turbine bearing cavity vent system. The pressure regulating valve contains an evacuated bellows and valve assembly. This regulates the pressure in the gearbox by positioning the valve seat away or towards the gearbox orifice depending on pressure altitude. Any excess pressure is spilled via the exhaust duct. Thus, if the relative pressure in the gearbox decreases i.e. at a higher altitude, the evacuated bellows senses this atmospheric pressure drop and expands to close the valve against the gearbox orifice. The gearbox pressure will then increase. A seperate pressurizing air supply is fed to the load compressor roller bearing area.
Gearbox Pressurization - Schematic
Figure 002
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