(c)  
Reset

 1)  When the autopilot is disengaged with the A/P disengage switch, the warnings are reset on the second press of the switch. Reset of an autopilot disengage warning due to any other means of disconnect is achieved by pressing the control wheel disengage switch once.
 B.  Autopilot/Flight Director System Signal Source Fault Detection (SSFD) (Fig. 10)
 (1)  Signal Source and Fault Detection provides independent selection and monitoring of sensor input data in each FCC. Signal Selection is provided to maintain servo tracking during multi-channel operation and when dual flight directors are selected. Monitoring sensor data allows detection of a failed sensor and permits exclusion of the invalid data from autopilot servo and flight director command computations. The SSFD also provides failure flags for ASA, Caution, and mode fail annunciations. There are three types of SSFD algorithms utilized for triplex, discrete, and dual/single source sensors.
 (a)  Mediam Select SSFD Process computes the mid-value of triplex
 (3) sensor inputs.
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 ALL  ú ú 04 Page 22 ú Dec 20/93
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A
757
MAINTENANCE MANUAL

ENABLE 2 EQUALIZATION MID PITCH &ROLL
LOCAL DATAVALUE SELECTED DATALOCAL DATA
INPUT
SELECTOR MODE 7
MONITOR
LOGIC ENABLE
ALOCAL FAILENABLE
FAULT
DETECTION
LOCAL COMPUTATION (SSFD)
L DATA CROSS
SAME AS LOCALL DATA
LOCAL FAIL
CHANNEL

FAIL L COMPUTATION (SSFD)L FAILANY FAIL
MONITOR SELECTED
LOGIC
PARAMETERFAILARM/
R DATA TWO FAIL
SAME AS LOCAL R DATA
ENGAGE SELECT
INPUT LOGIC
R COMPUTATION (SSFD) R FAIL FAIL LOCAL SIGN STATUS SELECT
MATRIX VALID
LOCAL PARAMETER

INPUT
NORMAL
1ACTIVITY SSM
SELECTLOGIC
TWO SSM VALID
GS í 60 KTS
FAIL
L SSM VALID
SQ1 F/D ON
SELECT L PARAMETER ACTIVITY CMD ENGA
SOFTWAREL X-CHANNEL VALID
HARDWARER SSM VALID
IRS, SURF
R PARAMETER R POS, RWY
LOCAL FAIL
ACTIVITY 1FOR THE FOLLOWING
HDG VOTE
FAIL
R X-CHANNEL VALID PARAMETERS:
ANY FAIL
GS . 40 KTS
LOGIC
LOGIC
LOCAL STAB. POS VALID PITCH ANGLE, PITCH RATE,
TWO FAIL
L STAB. POS VALID
ROLL ANGLE, ROLL RATE,L X-CHANNEL VALID
ONE SSM VALID
MAG HDG, YAW RATE, TRUER STAB. POS VALID
HDG, GND SPD TRUE TRACK
SIGN STATUS LOC SEL ANGLE, MAG TRACK ANGLE
R X-CHANNEL VALID MATRIX (SSM)
VERT ACCEL, LATERALINPUT
APP SEL B  2
ACCEL, NORM ACCEL, CROSSSELECT
TK ACCEL, ALONG TK ACCEL,
PITCH
MODE

FLT PATH ACCEL. SEL RWYSQ
3 HDG; STAB. POS; FLAP
LOGIC G/S ACTIVE4 2
POS; AIL SURF POS, ELEVFAIL
SURF POS, RUD SURF POSRA . 1500'
ONE SSM VALID
5
SELECT ILS FREQ CHANGE 6
2 RADIO SIGNALS: G/S DEV,ARM/
R
LOC DEV, RADIO HEIGHTENGAGE
GO AROUND SEL 6
SELECTED3 LOC DEV
RA í 400'
DATA
LOGIC
4 G/S DEV SQ
A
5 RADIO HEIGHT
ROLL

RADIO 6 LOC DEV & G/S DEV
MODE  LOC ACTIVE
SIGNALS
LOGIC

B R
7 FOR ATTITUDE RATE ANDLOGIC
VOTE ACCELERATION SIGNALSGND IS USED NOTSELECTED DATAFLIGHT CONTROL COMPUTER (TYPICAL)
Autopilot/Flight Director System Signal Source Fault Detection (SSFD) Schematic
Figure 10 (Sheet 1)

EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITHOUT CONTROL ú

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A
757
MAINTENANCE MANUAL

ENABLE 2 EQUALIZATION MID PITCH &ROLL
LOCAL DATAVALUE SELECTED DATALOCAL DATA
INPUT
SELECTOR MODE 7
MONITOR
LOGIC ENABLE
ALOCAL FAILENABLE
FAULT
DETECTION
LOCAL COMPUTATION (SSFD)
L DATA CROSS
SAME AS LOCALL DATA
LOCAL FAIL
CHANNEL

FAIL L COMPUTATION (SSFD)L FAILANY FAIL
MONITOR SELECTED
LOGIC
　
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