(12)
 Equipment Cooling Smoke Detection (26-16-50)

 (a)  Smoke in the equipment cooling system is sensed by a smoke detector installed between the supply air duct and exhaust air duct. The pressure differential between the ducts causes a continuous flow of air through the detector for sampling. If smoke condition is established by the smoke detector, a discrete signal is sent to EIU and a EICAS message is created.

 (13)
 Wheel Well Overheat Detection (26-17-00)

 (a)  The wheel well overheat detection circuit uses eight single element sensors, two in each of the four wheel wells. These are connected to form a single continuous loop. An increase in temperature in any wheel well area provides a overheat indication to the flight crew. A test switch is provided on the pilots' overhead panel. The flight crew will be notified of overheat condition by a caution EICAS message.

 (14)
 Wing Leading Edge Overheat Detection (26-18-00)

 (a)  There are thermal switches located in the leading edge of each wing and two thermal switches in each nacelle strut. The thermal switches are wired in paralled, and closure of any one will provide overheat warning on EICAS. The two thermal switches in each nacelle strut are set to close at 300°F. The four thermal switches located in nacelle strut areas of the wing are set to close at 250°F and the 14 thermal switches located away from the nacelle struts are set to close at 200°F. The flight crew will be notified of overheat conditon by caution EICAS messages.

 (15)
 Tail Cone Overheat Detection System (26-19-00)

 (a)  The tail cone overheat detection system senses excessive air temperature around the APU bleed air duct. Twenty thermal switches are installed along APU bleed air duct. An overheat condtion caused by leakage or rupture in the duct causes the thermal switch to close, creating an EICAS message and illuminate an indicator light on P83 panel.
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 26-10-00
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 DETECTION - ADJUSTMENT/TEST
___________________________
 1.  General_______
 A.  This procedure contains these fire detection operational tests which use the FIRE/OVHT test switch on the miscellaneous switching module, M7317:
 (1)  
the engine fire/overheat

 (2)  
the APU fire

 (3)  
the lower cargo compartment smoke

 (4)  
FREIGHTERS OR COMBIS;
 The main deck cargo compartment smoke

 (5)  
the wheel well overheat

 (6)  
the leading edge overheat system.

 B. The FIRE/OVHT test switch is on the pilots' overhead panel, P5, on the miscellaneous switching module, M7317, in the flight compartment.
 TASK 26-10-00-715-001
 2.  Operational Test for Fire/Overheat Detection Systems____________________________________________________
 A.  References
 (1)  
AMM 24-22-00/201, Manual Control

 (2)  
SSM 26-11-01 thru SSM 26-11-04, SSM 26-15-01, SSM 26-16-01, SSM 26-17-01, SSM 26-18-01 and SSM 26-18-02

 (3)  
WDM 26-11-11 THRU WDM 26-11-43

 (4)  
WDM 26-15-11

 (5)  
WDM 26-16-11

 (6)  
WDM 26-17-11

 (7)  
WDM 26-18-11 THRU WDM 26-18-18

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

 C.  Prepare for Test
 S 865-002
 (1)  Supply electrical power (AMM 24-22-00/201).
 D.  Operational Test
 S 865-029
 (1)  Close these circuit breakers on the overhead circuit breaker panel, P7:
 (a)  
7F23, LANDING GEAR DSP & CONT ALTN

 (b)  
7H14, CARGO SMOKE DETECT LWR A

 (c)  
7H15, CARGO SMOKE DETECT LWR B

 (d)  
7H16, CARGO SMOKE - MAIN DECK ZN 1-8 DET A

 (e)  
7H17, CARGO SMOKE - MAIN DECK ZN 1-8 DET B

 (f)  
7H18, CARGO SMOKE - MAIN DECK ZN 9-16 DET A

 (g)  
7H19, CARGO SMOKE - MAIN DECK ZN 9-16 DET B

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