(3)  
For a test of the aft cargo compartment temperature sensor, refer to AMM 21-61-00/501.

 B.  The high temperature switch is a 50 degrees F (10 degrees C) switch.
 C.  The system uses four thermal switches to control the aft cargo heat valves. A low temperature and a high temperature control switch and an overheat switch are installed on the left sidewall of the bulk cargo compartment. The switches are installed adjacent to the bulk cargo compartment temperature sensor, in the sensor assembly box. An underfloor temperature control switch is installed below the bulk cargo floor, inboard of the bulk cargo door. The switch set points are as follows:
 SWITCH______ OPEN TEMPERATURE________________ CLOSE TEMPERATURE Low Temperature 50°F (10°C) max 40°F (4°C) min High Temperature 60°F (16°C) max 50°F (10°C) min Overheat 80°F (26°C) min 90°F (32°C) max Underfloor control 42°F (6°C) max 32°F (0°C) min
 TASK 21-44-00-705-001
 2.  Cargo Compartment Heating System Ground Test____________________________________________
 A.  General
 (1)  
The ground test for the cargo compartment heating system commands the aft cargo heat valves to close and then to open fully. The valves fail if they do not move to their commanded positions.

 (2)  
The cargo compartment heating system ground test does not do a test of the forward cargo heating system or the bulk cargo heating system.

 B.  References
 (1)  
AMM 24-22-00/201, Manual Control

 (2)  
AMM 36-00-00/201, Pneumatic System

 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 21-44-00
 ALL  ú ú 10 Page 501 ú Feb 18/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 C. Access
 (1)  Location Zones
 221 Control Cabin, LH
 222 Control Cabin, RH

 D. Prepare for the Test
 S 865-002
 (1)  
Supply electrical power (AMM 24-22-00/201).

 S 865-003

 (2)
Release the pressure in the pneumatic system (AMM 36-00-00/201).

 S 865-004

 (3)  
Make sure the AFT CARGO HT switch-light, on the overhead panel, P5, is in the off position.

 S 865-041

 (4)  
Prepare the CDU for the test:

 (a)  
Push the MENU key on the CDU to show the MENU.

 (b)  
Push the line select key (LSK) that is adjacent to <CMC to show the CMC MENU.

 (c)  
If <RETURN shows after you push the LSK, push the LSK that is adjacent to <RETURN until you see the CMC MENU.

 (d)  
Push the LSK that is adjacent to <GROUND TESTS to show the GROUND TESTS menu.

 (e)  
Push the LSK that is adjacent to <AIR CONDITIONING to show the GROUND TESTS for the air conditioning system.

 (f)  
Push the NEXT PAGE key until you find <CARGO HEAT SYSTEM.

 NOTE: If INHIBITED shows above <CARGO HEAT SYSTEM, the
____
 test will not operate.

 (g)  If INHIBITED shows above <CARGO HEAT SYSTEM: 1) Push the LSK that is adjacent to the test prompt. 2) Do the steps shown on the CDU. 3) Push the LSK that is adjacent to <RETURN to show the ground
 test menu again.
 E. Cargo Compartment Heating System Ground Test
 S 745-042
 (1)  Push the LSK that is adjacent to <CARGO HEAT SYSTEM.
 NOTE: IN PROGRESS shows during the test.
____
 S 745-043
 (2)  When IN PROGRESS goes out of view, look for PASS or FAIL> adjacent to <CARGO HEAT SYSTEM.
 NOTE: If PASS shows, no failures occurred during the test.
____
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 21-44-00
 ALL  ú ú 06 Page 502 ú Feb 18/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 S 745-044
 (3)  If FAIL> shows:
 (a)  
Push the LSK that is adjacent to FAIL> to see the GROUND TEST MSG page for the failure.
　
中國航空網 m.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：747-400 AMM 飛機維護手冊 空調 AIR CONDITIONING 1(155)