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 5)  At this point, the faulty RVDT has not yet been determined. The threshold monitors only detect a difference in the command and feedback signals. They cannot determine which is in error. That is left to the maintenance monitor.
 (c)  AIRPLANES WITH -100 SERIES SCMs; Maintenance Monitor 1) The maintenance monitor uses a comparator circuit for
 transducer inputs to the A and B subchannels of the SCM and a voting logic circuit which uses inputs from all three SCM comparator circuits to determine which transducer is at fault. Identical circuits monitor the RVDTs and the LVDTs (Fig. 10).
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A

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MAINTENANCE MANUAL

SPEED BRAKE LVDTS
1A  1B 2B
2A 
3A  3B 

CAPTAIN'S
FIRST OFFICER'S
CONTROL WHEEL
CONTROL WHEEL
RVDTS
RVDTS

SPOILER PCA RVDTS
* = BAD RVDT
A = ACTIVE SUB-CHANNEL B = STANDBY SUB-CHANNEL C = MODEL SUB-CHANNEL

= SUB-CHANNEL DETECTING ERROR
Redundancy Management
Figure 9

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MAINTENANCE MANUAL

SPEED BRAKE LVDTS

* = BAD RVDT A = ACTIVE SUB-CHANNEL B = STANDBY SUB-CHANNEL C = MODEL SUB-CHANNEL
NOTE:
COMPARATOR OUTPUT = 1 IF INPUTS DISAGREE

Maintenance Monitor Transducer Failure Detection Figure 10
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MAINTENANCE MANUAL

SPEED BRAKE LVDTs 1
1A  2B 1B 
2A 
3A  3B 

CAPTAIN'S
FIRST OFFICER'S
1
CONTROL WHEEL
CONTROL WHEEL
RVDTs
RVDTs

 

 

 

 

 

 

CSEU-L (EXAMPLE)
* = BAD RVDT
A = ACTIVE SUB-CHANNEL
B = STANDBY SUB-CHANNEL
C = MODEL SUB-CHANNEL

THESE COMPONENTS HAVE EQUIVALENT CIRCUIT CONNECTIONS TO THE SCMs AS THE CAPTAIN'S CONTROL WHEEL RVDTs
Maintenance Monitor Transducer Failure Detection
Figure 10A

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MAINTENANCE MANUAL

 2)  The comparator produces a logic one if the two inputs disagree and a logic zero if they agree. Output (X, Y, and Z in Fig. 10) is fed to all three SCMs. In the example above, SCM 1L compares RVDTs #1 and #2 which produces a logic one at X since the two signals disagree. SCM 2L compares RVDTs #1 and #3. Since both agree, the comparator outputs a logic zero at Y. SCM 3L, comparing RVDTs #2 and #3, produces a logic one at Z since the two do not agree.
 3)  The required input for the voting logic is 1-1-0 on the three leads to the AND gate. The logic used to set the faultball is a VOTE FAIL and a "switch" decision. This condition is met, in the example, only in SCM 3L. Therefore, the RVDT faultball (CW XDCR) is set on this SCM.
 4)  The faultball will always be set on the SCM whose active subchannel, A, is receiving input from the faulty transducer (RVDT or LVDT). Table 1 identifies which control wheel or speedbrake lever transducer is at fault when a given faultball is set.
 Table 1: Control Wheel and Speedbrake Lever Faultballs
　
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