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AIR CYCLE SYSTEM - ADJUSTMENT/TEST

1.  General
A.  This procedure has these tasks:
(1)  
Air Cycle System Test

(2)  
Pack Protective Circuit Test

B.  These tasks are presented to check air cycle system components which require only electrical power for their operation. The remaining air cycle system components which require air flow, or pressure, for their operation must be checked with the engine bleed air distribution system components (Ref 21-11-0, Adjustment/Test). Duck leakage is checked in 36-11-0, Adjustment/Test.
C.  The following tasks utilize pack valve position with respect to several steps in the procedure. Since the ducts are not pressurized the pack valve will not be repositioned in response to electrical control. In order to accomplish this test, therefore, it is necessary to remove the electrical connector form the pack valve limit switch and to keep a person stationed at the pack valve to determine simulated operation of the valve. A click will be felt, or heard, at solenoid A of the pack valve during the step in which pack valve is supposed to open or close.
2.  Air Cycle System Test
A.  General
(1)  This test checks the operation of the pack valve and makes sure the overheat switches close when an overheat condition occurs.
B.  Equipment and Materials
(1)  Temp-Cal Probe Heater BH-3884-40 (Attachment to Jet Cal engine analyzer) or H294 Temp-Cal Thermal Switch Tester or H394 Temp-Cal Tester with adapter cable BH405. BH24944 Heater Probe Kit (basic P/N).
NOTE:  This kit is necessary to use the testers listed above. Consult with the supplier for the appropriate dash number for a specific airplane model and tester combination.
HOWELL INSTRUMENTS, 3479 WEST VICKERY BLV., FORT WORTH TEXAS 76107
C.  Prepare Air Cycle System for Test
(1)  
Provide electrical power.

(2)  
Check that all air conditioning circuit breakers are closed (in).

(3)  
Check that the following circuit breakers on circuit breakers 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)

(4)  
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.

(b)  
Move LIGHTS switch to BRT.

(c)  
Press to test PACK TRIP OFF light.

(d)  
While pressing PACK TRIP OFF light, move LIGHTS switch to DIM and check that light dims.

(e)  
Continue to press PACK TRIP OFF light, move LIGHTS switch to BRT and check that light brightens.

(5)  
Check that air conditioning PACK switch is in OFF position.

(6)  
Open air conditioning equipment bay door.

(7)  
Simulate open position of pack valve.

(a)  
Open OVERHEAT circuit breaker.

(b)  
Remove connector from pack valve limit switch. (See figure 501.)

(c)  
Close OVERHEAT circuit breaker.

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D.  Test Air Cycle System
(1)  
Move air conditioning PACK switch to ON and check for a click at solenoid A of the pack valve.

(2)  
Move temperature selector knob toward MANUAL WARM to drive mix valve away from the full cold position.

(3)  
Check compressor discharge overheat switch operation.

(a)  
Remove compressor discharge overheat switch from air cycle machine compressor scroll.

(b)  
Apply controlled heat to overheat switch probe while observing MASTER CAUTION light and AIR COND annunciator light on P2-1 panel and PACK TRIP OFF light on forward overhead panel.

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500  Pack Valve Location 
Jul 15/70  Figure 501 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  21-51-0 Page 503 
　
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