(2)
Computer No. 2 (right) is powered from the 28v dc bus 2 and the 28v ac transfer bus 2. Computer No. 2 receives an angle of attack signal from the right AOA sensor. Other signals are supplied to the computer by the right outboard >60 knots discrete switch in the auto speedbrake module and by the flaps greater than 10 degrees switch (S138). Computer No. 2 controls solenoid No. 2 in the autoslat control valve.
B.
Autoslat Computer Indicator Lights
(1)
LED indicator lights on the face of each computer give autoslat system status and fault information for testing and trouble shooting. The circuitry which controls the operation of each light is described as follows:
(2)
PWR OK light
(a)
The green PWR OK light is on when there is no fault with the autoslat computer's power sources and internal power supplies.
(b)
28v dc is used to energize relays in the computer and to activate the solenoid coil in the autoslat control valve. 28v ac is used for AOA sensor excitation and to generate +18v dc and -18v dc for circuits in the computer.
(c)
A power monitor circuit in the computer continuously monitors the 28v dc, 28v ac, +18v dc, and -18v dc power. With all these sources operating properly, the PWR OK light is on. If one or more power sources fails, the PWR OK light goes off and the computer disables itself.
(3)
AUTO EXT light
(a)
The amber AUTO EXT light comes on to indicate that an automatic extension of the leading edge slats is being commanded by the computer.
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27-83-00
COMPUTER P/N 65-52818 ú CONFIG 1 ú 02 Page 2 ú Mar 15/92
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
Autoslat Computer Installation
Figure 1
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH AUTOSLAT ú
27-83-00
COMPUTER P/N 65-52818 ú CONFIG 1
ú 01 Page 3
ú Mar 15/90
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
(b) Each autoslat computer has two independent computation paths which process the same angle of attack signal. One path controls the 28v dc applied to the "hot" wire (H leg) of the solenoid coil in the autoslat control valve. The other path controls access to dc ground for the "cold" wire (C leg) of the same coil. Both paths must switch their leg on simultaneously to cause an autoslat extension. Each path contains an AOA synchro to analog circuit, a scaler/filter circuit, a summer/output circuit, and a valve coil relay. 1) The synchro to analog circuit transforms the AOA sensor
signal into an analog dc voltage. The scaler/filter circuit scales and offsets the analog dc voltage. It also uses a low pass filter to smooth out any rapid variations in AOA vane movement from air turbulence.
2) The summer/output switch circuit combines the modified AOA sensor signal with signals from the air/ground relays and the autoslat computer fault detectors. This circuit turns on an output switch when an autoslat extension is computed.
3) The autoslat valve solenoid coil relays are energized by the output switches of the summer/output switch circuits. When both relays (H leg and C leg) are energized simultaneously, the slats extend and the AUTO EXT light comes on.
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