(4)  
Remove the clamp and sleeve from the transition.

 (5)  
Remove the transition and clamp from the air inlet.

 S 034-004
 S 034-005
 S 034-006
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A
747-400
MAINTENANCE MANUAL

DETECTOR

SLEEVE
(4 LOCATIONS)
SMOKE DETECTOR

Equipment Cooling Smoke Detector Installation
Figure 401

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747-400 MAINTENANCE MANUAL
 S 034-017
 (6)  
Remove the transition and clamp from the air outlet.

 S 034-007

 (7)
Remove the four screws and washers that hold the detector.

 S 024-008

 (8)  
Remove the smoke detector.

 TASK 26-16-51-404-009
 3.  Install the Smoke Detector (Fig. 401)__________________________
 A. References
 (1)  
AMM 21-58-00/501, Equipment Cooling System

 (2)  
AMM 25-52-01/401, Containerized Cargo Compartment Ceiling and Sidewall Linings

 (3)  
AIPC 26-16-01, Fig. 5

 (4)  
WDM 21-58-12

 B. Access
 (1)  Location Zone 121 Forward Cargo Container Compartment Forward Half LH
 C. Procedure
 S 424-010
 (1)  
Install the detector with the four screws and washers.

 S 434-011

 (2)  
Install the clamp and transition to the air inlet.

 S 434-012

 (3)  
Install the clamp and transition to the air outlet.

 S 434-018

 (4)  
Install the clamp and sleeve to the transition.

 S 434-013

 (5)  
Install the electrical connector, DM7931, on the smoke detector.

 S 414-014

 (6)  
Install the left sidewall lining panel in the forward cargo compartment at STA 581 (AMM 25-52-01/401).

 S 864-015

 (7)  
Remove the DO-NOT-CLOSE tag and close this circuit breaker on the main power distribution panel:

 (a)  6J35, E/E COOLING SMOKE IND TEST
 S 714-016
 (8)  Do the Operational Test for the equipment cooling system (AMM 21-58-00/501).
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747-400 MAINTENANCE MANUAL
 WHEEL WELL OVERHEAT DETECTION SYSTEM - DESCRIPTION AND OPERATION
________________________________________________________________
General
_______
 A.  A continuous loop sensor system is installed in the left and right wing and body wheel wells to detect an overheat condition in these areas. The detection elements are connected together to act as a single unit to provide fire (overheat) alarms to the flight crew.
 B.  When the temperature reaches a set point, the element impedance drops significantly. The control card detects the impedance drop and produces an EICAS caution message.
 C.  The fire/overheat test module checks loop continuity and integrity of the
 circuit.Wheel Well Overheat Detector Elements (Fig. 1)
_____________________________________
 A.  There are eight detection elements connected in series, forming a single continuous loop overheat detection circuit. The detection elements are mounted to the upper fire wall by teflon impregnated asbestos bushings.
 B.  The detection element consists of an inconel tube filled with a salt-impregnated ceramic core and a single nickel wire. The single nickel wire imbedded in this core is the power lead, and the inconel shielding is grounded.
　
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