(2)
FIRE PROTECTION DETECTION - ENG NO. 2
(3)
FIRE PROTECTION DETECTION - APU
B. Press on the latch to let the levers move away from handle.
C. Move the levers down to force the unit away from the shelf-mounted connector.
D. Remove the unit from the shelf.
NOTE: To prevent foreign object contamination or damage, cover all ports, openings and electrical connectors of unit or shelf with plastic caps or bags.
500
Oct 20/90 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 26-10-01 Page 401
Electrical/Electronic Black Box Installation 500
26-10-01 Figure 401 Oct 20/90
Page 402
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
3. Install Engine and APU Fire Detection Accessory Unit (Fig. 401)
CAUTION: ELECTRICAL PINS ON E/E BOX CONNECTOR AND TRAY CONNECTOR MUST NOT BE BENT OR DAMAGED. INSTALLATION OF E/E BOX WITH DAMAGED PINS COULD RESULT IN DAMAGE TO E/E BOX, TRAY ELECTRICAL CONNECTOR, OR SYSTEM COMPONENTS.
A. Slide the unit into shelf with the levers in the open position until the levers engage in the shelf-mounted fork.
NOTE: Remove any protective caps or bags from unit or shelf prior to installation.
B. Move lever-latch to its locked position.
(1)
The connectors shall mate to the dimensions of detail B (Fig.\401).
(2)
If necessary, adjust the fork so that with connector properly mated and the lever open 0.50 to 0.60 inch from the locked position, the fork just puts pressure on the lever (Ref 20-10-111).
C. Do the engine fire detection system test (Ref Engine Fire Detection System - Adjustment/Test).
D. Do the APU fire detection system test (Ref APU Fire Detection System - Adjustment/Test).
E. Restore airplane to normal.
500
Oct 20/90 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 26-10-01 Page 403
ENGINE FIRE DETECTION SYSTEM - DESCRIPTION AND OPERATION
1. General
A. The engine fire detection system provides fire detection for each engine and firewall. Fire detection is provided by shrouded sensing elements mounted on the engine side of the horizontal fire wall and along the bottom of the engine (Fig. 1). The detection system is an electrical heat sensing system that responds to a general overheat condition or a localized fire condition by activating warning lights and an alarm bell.
B. The engine fire detection system consists of the fire protection system module, engine and APU fire detection accessory unit (control module), alarm bell, master warning and caution lights and sensing elements. Each engine fire detection system consists of high (fire) and low (overheat) thermistor type sensors enclosed in a shroud. Each sensor is connected to the transistorized engine and APU fire detection accessory unit. The accessory unit contains the high and low detector control cards, test circuits and warning component control circuits. For APU coverage, refer to 26-15-0, APU Fire Detection System. The high or low detector control card monitors the electrical resistance of their associated sensors. The control card circuit discriminates between a fire and overheat condition or a short circuit. The overheat or fire warning lights and alarm bel1 will actuate when a temperature rise causes the sensor resistance to drop to the design value corresponding to the alarm temperature. The detector inoperative light will illuminate when a short is sensed in the detection circuit.
C. The engine fire detection system can be tested in flight or on the ground by operation of the fire test switch (Fig. 2). The fire test switch circuit checks continuity through the system by electrically simulating a fire or overheat condition on both engines. This energizes overheat warning lights or the alarm bell and fire warning lights. The detector test switch (on engine and APU fire detection accessory unit) supplies a ground across the control card sensing element terminals, causing the detector inoperative lights to illuminate.
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