b)

c)
d)
e)
f)
g)
757
MAINTENANCE MANUAL

Invalid data or the loss of the F/D-on bit, removes the command bars and shows a rectangular FD failure flag (yellow with black letters) in area 5. Command bars are removed if an NCD condition exists; no flag is displayed.
 NOTE: AIRPLANES WITH -420 AND SUBSEQUENT EFIS SYMBOL
____ GENERATORS;
 If the airplane is on the ground and the FCC
 circuit breaker for the selected FCC is open,
 the FD failure flag will not show.Invalid data removes the speed deviation scale and pointer and draws a rectangular SPD failure flag (yellow with black letters) in area 6. An NCD condition removes the pointer but the scale remains.If the TMS SPD DEV ERROR option is active, a speed error greater than |10 knots from the commanded speed index is indicated on the EADI. The speed deviation pointer changes color to yellow and flashes at 0.9 Hz.Invalid data removes LOC and/or G/S scales and pointers and draws LOC and/or G/S faulure flags in area 12 and area 8 respectively. Failure flags are yellow with black letters. An NCD condition removes the pointer but not the scale.Provision for a ILS Deviation Monitor is available as an option. The ILS Deviation Monitor is enabled when any A/P is in APP (after LOC and G/S capture) and either the LOC or G/S exceeds the critical values below for more than one second. (The ILS DEV WARN program pin on the SGs must be grounded.) The critical value for LOC is more than 0.0155 DDM BELOW 500 FEET: FOR G/S, more than 0.0875 DDM between 500 and 1000 feet.The ILS deviation monitor is indicated by a flashing (1 Hz) LOC or G/S deviation pointer and a change in scale color from white (normal) to yellow (caution).
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A
757 MAINTENANCE MANUAL
 h)  Invalid and NCD data remove FMA characters of the affected display (areas 8, 9, 10, 11, 13, 14, 15). When an FMA FAULT bit is set in a specific AFDS discrete input word, a horizontal line is drawn through the center of the displayed annunciation.
 i)  Invalid data removes numerics and FT letters. No computed data draws five dashes in place of numerics but retains the FT legend.
 B.  BITE and Monitor
 (1)  
The FCC provides in-flight detection of AFDS and related component failures. Detection includes:

 (a)  
System fault detection and fault location.

 (b)  
Monitoring of servos, sensors, input interfaces, and output interfaces.

 (c)  
Self test.

 (d)  
Storage of identified faults.

 (2)  
Fault Detection and Location

 (a)  
Faults are detected through self tests, system monitors within the FCC, and external fault data from interfacing LRUs. The FCC also receives hydraulic valid signals to aid in fault location.

 (b)  
The FCC, in conjunction with the MCDP, can identify the location of an in-flight detected failure to the FCC itself, to a specific interfacing LRU, or to a functional group of LRUs.

 (3)  
Monitoring

 (a)  
The FCC monitors variable and discrete inputs and internally generated valid signals, including: 1) Servo loop operation. 2) Flap and stabilizer position. 3) Hydraulic power. 4) Data bus operation. 5) Status words. 6) Input signal fault. 7) Input signal tolerance. 8) Valid discretes. 9) Internal AC and DC power.

 (b)  
The FCC monitors all incoming and outgoing interfaces, checking data for reasonableness and checking sign status matrix bits on data buses. The FCC also makes cross channel data comparison with other FCCs.

 (4)  
In-flight Self Test

 (a)  
The in-flight self test is performed by hardware and software independently in each of the FCCs. Safety critical functions are tested at least once a second. Non-critical functions are tested at least once every ten seconds.

 (b)  
Faults detected by FCC self-test are stored in memory for access by shop support equipment. A maximum of five faults can be stored at one time. This fault data can only be removed from memory in the maintenance shop.

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