D01433
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GUN 001-050, 052-999 ú 22-12-00
ú ú 05 Page 57 ú Dec 20/94
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A
757 MAINTENANCE MANUAL
COMMAND ENGAGE SWITCHES
CAPTAIN'S FIRST OFFICER'S
APPROACH MODE
FLIGHT DIRECTOR FLIGHT DIRECTOR
SELECT SWITCH/LIGHTS
ON/OFF SWITCH ON/OFF SWITCH
GLIDE
SLOPE CL
SEE D
SEE E
1500 FT
50 FT SEE F
500 FT
RUNWAY THRESHOLD
___________________ FLARE ENGAGE____________ _______________
MULTICHANNEL ENGAGE NOSE WHEEL DOWN
. LOC AND G/S CAPTURED . FLARE STARTS AT 50 FT . BEGINS AT RADIO ALTITUDE . OTHER CHANNELS ARMED GEAR HEIGHT LESS THAN 5 FT MANUALLY OR AUTOMATICALLY . THROTTLE RETARD COMMAND TO . NOSE DOWN ELEVATOR THROUGH . MULTICHANNEL ENGAGE AUTOTHROTTLE 3 SEC EASY ON AT 1500 FT RADIO ALTITUDE . VERTICAL POSITION CONTROL TO . FLARE ARMED ANNUNCIATION POINT 500 FT PAST GLIDE SLOPE
F
AT MULTICHANNEL ENGAGE INTERCEPT-2 FPS DESCENT RATE
AT TOUCHDOWN
D
E
Pitch Channel - Autoland
Figure 17 (Sheet 2)
C70595
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. GUN 051 ú
22-12-00
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
757
MAINTENANCE MANUAL
(b)
The autothrottle sets the go-around thrust unless it is during takeoff when in the THR HOLD mode. When the go-around switch is pushed while in the TO mode, all the performance derates are cancelled and the EPR pointers move to maximum takeoff thrust. When THR HOLD is on, the throttles must be operated manually.
(c)
When the windshear conditions go away, the autoflight system smoothly changes back to the usual takeoff or go-around mode.
(d)
If the windshear system turns on with the flight directors off, the flight director command bars come on automatically and give the applicable commands, and the ADIs show GA. When the windshear condition is gone, the flight directors can be reset (command bars off) by selecting an AFDS mode, or by setting the flight director switches off, then on.
(23) Autoland Flight Path Control Logic (Fig. 10)
(a)
Upon receipt of the APP mode ARMED or OPERATIVE discrete, the APP switch dot-bar matrix is illuminated to indicate request accepted. Each CMD ENGAGE switch initiates a CMDENG request discrete which goes to its corresponding FCC. A valid request generates a REQUEST ACCEPTED discrete which latches the CMD switch in the up position. Each F/D switch generates an ON/OFF discrete, but there is no visual feedback to the switches.
(b)
Command Engage Sequence Detection Logic
1) Each FCC receives CMDENG REQUEST ACCEPTANCE logic from the other two FCCs via the cross-channel bus and records the order in which each become CMDENG. One of the discretes (L FIRST, C FIRST, R FIRST) is supplied to the first-in-command detection logic. This logic determines which FCC will supply FMA signals to the EFIS. It identifies LOCAL FIRST IN COMMAND and FOREIGN channels during multi-channel engage. On detection of a failure in the first-in-command channel, the fail sequence logic selects a different channel to be first-in-command.
(c)
Autoland Processing Logic
1) The APP mode request generates the APPROACH ARM logic when the F/D disengage logic is zero. This is applied to the localizer logic as an alternate to the LOC mode arm logic and is also used in autoland logic.
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