H27586
Engine Fire Detection System Component Location 513
26-11-0 Figure 1 (Sheet 1) Feb 20/87
Page 2
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
L20621
514 Engine Fire Detection System Component Location
May 20/82 Figure 1 (Sheet 2) 26-11-0
Page 3
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
H27607
Engine Fire Detection System Schematic 513
26-11-0 Figure 2 Feb 01/76
Page 4
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
B. Overheat Detector Switch
(1)
Two double-throw, locking, toggle actuated overheat detector switches permit selection of the overheat detection system as the primary fire detection system if the fire detection system for the associated engine has a malfunction. In the NORM (locked) position, the overheat and fire warning indicators are connected through the overheat detector switch to the applicable high and low temperature detector control cards in the engine and APU fire detection accessory unit. In the FIRE position, the low temperature detector control card is connected to the fire warning indicators and the high temperature control card and overheat warning indicators are isolated from the system (Fig. 2). The switch is locked in the NORM position. FIRE is selected by lifting the handle assembly out of detent and moving the toggle to the FIRE position.
(2)
Fire and overheat sensors are on each engine to provide a greater degree of airplane dispatch readiness and to give a clearer indication of an overheat of fire condition. The fire detection system used, is dependent on the overheat detector switch position. If the fire (high temperature) detector system on one engine becomes inoperative and fails to test satisfactorily before an airplane is dispatched, the overheat detector switch may be moved to the FIRE position. The airplane may then be dispatched.
C. Master Caution Lights Control Section
(1)
The master caution lights control section provides control of the master caution lights and the overheat detector annunciator light on lightshield module P7. The control section is a solid state switching circuit.
(2)
When an overheat condition occurs from either engine, the appropriate overheat detector control card provides a 28-volt dc signal to the control section. The control section provides a ground which allows the master caution lights and overheat detector annunciator light to illuminate. The control section may be reset by pressing the lens cap of either master caution light. When the lens cap is pressed, the light circuit is broken and a silicone controlled rectifier (SCR) in the control section will stop conducting, thus removing the ground and turning out the lights. The associated part of the control section will remain reset until the master caution lights and annunciator light are recalled by pressing the annunciator lights panel.
500
Aug 15/67 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 26-11-0 Page 5
D. Warning Lights
(1)
Red fire warning lights in the fire switch handles provide engine ready fire warning. The warning lights are normally connected to the fire detector control card of the associated engine. The lights may be connected to a overheat detector control card through the overheat detector switch in the event of a high temperature card malfunction. A fire or overheat condition, as applicable, in either engine will cause steady illumination of the associated fire and master fire warning lights (Fig. 2). Each warning light consists of several bulbs covered by a red translucent plastic lens in the fire switch handle.
(2)
Amber engine overheat lights are provided for engine overheat warning. The overheat lights are normally connected to the low temperature detector control card of the associated engine. An overheat condition at either engine will cause the steady illumination of the associated overheat and master caution - annunciator warning lights (Fig. 2).
(3)
The overheat warning lights may be tested individually by a press-to-test feature or they are tested when the master test switch is closed.
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