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Schematic of the Cockpit Door-Lock System Figure 004
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(3) Buzzer 23MQ
The electrical buzzer 23MQ is installed in the ceiling panel 211HC of
the cockpit. A signal from the control unit 24MQ operates the buzzer.
(4) Toggle Switch 26MQ
The toggle switch 26MQ, installed in the COCKPIT DOOR panel 119VU is
a three position switch (UNLOCK, NORM and LOCK). The toggle switch is
spring-loaded so that it returns to the NORM position automatically.
The position NORM is the neutral position in which the closed cockpit
door is automatically locked. In the UNLOCK position, the cockpit
door is released so that you can push it open. When you select this
function it overrides or resets any previous operations. In the LOCK
position the operation of the buzzer 23MQ and the keypad 25MQ is
cancelled. After a pre-selected time between 5 min. and 15 min. the
operation is possible again.
R
R **ON A/C 106-149, 303-399, 401-499,
R (5) Top, Center and Bottom Electrical Release Strikes 30MQ, 31MQ and 32MQ
R The three electrical release strikes 30MQ, 31MQ and 32MQ are
R installed in the lavatory side wall opposite to the door latch
R mechanisms.
R Each electrical release strike has an aluminium housing which
R includes the solenoid, the plunger, the catch and the Polymer
R Positive Temperature-Coefficient (PPTC) assembly.
R The solenoid has two coils and one high-energy spring:
R - one coil (referred to as the push coil) pushes the plunger to the
R extended position
R - the other coil (referred to as the hold coil) holds the plunger in
R the extended position
R - the high-energy spring pulls the plunger to the retracted position,
R when the hold coil is de-energized.
R When the push coil is energized, the plunger extends and puts a load
R on the high-energy spring. If the plunger is fully extended, the push
R coil is de-energized and the hold coil is energized to hold the
R plunger in this position.
R When the hold coil is also de-energized, the high-energy spring
R retracts and the plunger moves quickly to the retracted position.
R All the electrical release strikes have an internal sensor, which
R operates the solenoid when it receives an applicable signal. Then,
R the plunger extends and the catch is blocked or it retracts and the
R catch is free.
R The PPTC assembly is a thermal fuse that prevents an overheat
R condition of the solenoid. This malfunction can occur during a
R blockage of the catch if the push coil stays energized.
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R
R The center electrical release strike (31MQ) has two external
R microswitches installed on the housing. One microswitch monitors the
R closed and locked condition of the center latch mechanism. When its
R tenon disengages from the catch,this causes the OPEN legend of the
R indication light 22MQ to come on. The other microswitch monitors the
R position of the catch to show an incoorectly locked condition. This
R can occur if the still extended plunger blocks the operated catch and
R prevents its movement.
R (6) Control Unit 24MQ
R The control unit 24MQ is installed in the overhead panel 20VU. This
R panel has the white legends CKPT DOOR CONT, the STRIKE TOP, MID and
R BOT and the CHAN 1 and CHAN 2.
R The control unit controls the logic (fault indications, time delays
R and door access control) of the cockpit door lock-system. It has two
R internal pressure sensors which starts the fault logic sequence if a
R rapid decompression in the cockpit occurs. This can also occur during
R the pressurization test of the fuselage.
R The microprocessor of the control unit receives signals from:
R - the toggle switch 26MQ
R - the key pad 25MQ.
R The microprocessor sends a signal to operate:
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