AIR CONDITIONING - MAINTENANCE PRACTICES
1. Pack Cooling System Performance Test
A. General
(1) The following procedure is developed for detection of system abnormalities using only airplane instrumentation. This procedure is intended to provide quick evaluation of system performance for scheduled maintenance checks and trouble shoot flight operation problems.
B. Reference Procedures
(1) 49-11-0, APU Power Plant Operating Procedure
C. Prepare for Air Conditioning Test
(1)
Check that all air conditioning and pneumatic circuit breakers are closed (in).
(2)
Check that the following circuit breakers on circuit breaker panel P6 are closed:
(a)
MASTER CAUTION (all except FUEL, if installed)
(b)
INDICATOR LIGHTS, MASTER DIM BUS (9 places)
(c)
DIM & TEST (1 place)
(3)
Check warning lights and annunciators.
(a) Place LIGHTS switch on lightshield panel (P2-l) to TEST. Check that both MASTER CAUTION lights, the AIR COND annunciator light and PACK TRIP OFF light come on.
(4)
Open air conditioning equipment bay door.
(5)
Operate both cabin temperature selectors on overhead panel to place mix valves in full cold position and leave both selectors in OFF MANUAL position. Check that both visual indicators on air mix valves in air conditioning bay, show full cold position. If not, repair temperature control system before proceeding (Ref 21-61-0, Conditioned Air Temperature Control Systems).
(6)
Place engine 1 and 2 BLEED switches on overhead panel to OFF position and APU BLEED switch to ON position.
(7)
Provide APU power (Ref 49-11-0).
NOTE: Electrical load to be less than 25 amperes.
(8)
Place both air conditioning (A/C) PACK switches to OFF position.
(9)
Place ISOLATION VALVE switch to OPEN position.
(10)
Record ambient temperature which is used for calculation in flow and heat exchanger check.
(11)
Record APU exhaust gas temperature (EGT).
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NOTE: This is used for calculation in flow check. Allow time for EGT to stabilize and tap indicator to remove hysteresis. Ensure valve positions, remain as stated, to avoid effect of leakage variance.
D. Test air conditioning system.
(1) Turbofan Valve Test
(a)
Remove both connectors from turbofan valve solenoids and manually override the valve opens. Check that the valve modulates to a position somewhere less than full open.
NOTE: Duct pressure should be higher than the valve maximum regulating pressure of 33 psi. A valve that is fully open is regulating too high.
(b)
Replace the connectors and turn both packs ON. Observe that the valves are full open.
NOTE: Duct pressure will be lower than the valve minimum regulating pressure of 27 psi. A valve that is not fully open is regulating too low.
(2) Flow and Primary Heat Exchanger Test
(a)
With both A/C packs ON, note APU EGT.
(b)
Turn off right pack (not under test), and remove connector from the left pack water separator 35-degree sensor. Check that APU EGT drops and duct pressure rises to above 27 psi.
NOTE: This ensures pack flow is regulated by the flow control, not by the APU load limiter. In hot ambient, APU load limit may occur normally. In that case, a finding of low flow condition in step (2)(e), is not valid.
(c)
Verify the 35 degree control valve has opened fully.
(d)
Check that water separator bag condition indicator is below red band.
NOTE: Indicator is in the red band, the bag is dirty and is restricting flow. 中國航空網 m.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：737 AMM 飛機維護手冊 AIR CONDITIONING 空調(8)
