A/P Engage Interlock Table
Figure 15
A737-300/400/500MAINTENANCE MANUAL
A
737-300/400/500MAINTENANCE MANUAL
(e) Item 5 - INTENTIONAL BLANK
(f) Item 6 - INTENTIONAL BLANK
(g) Item 7 - The A/P is normally disengaged by pressing the
disengage switch on the control wheel.
(h) Item 8 - Prior to engaging the A/P, the aileron pressure switch
must not be closed.
(i) Item 9 - The A/P aileron actuator is synchronized to the
surface prior to energizing the detent solenoid, when the A/P
is engaged in CWS or CMD. This action must be complete within
3.5 seconds from the time dc was applied to the actuator detent
solenoid.
(j) Item 10 - Same as (8) except elevator.
(k) Item 11 - Same as (9) except elevator.
(l) Item 12 - The FCC 115 volts ac must be valid. A delay allows
an interrupt of 0.5 seconds.
(m) Item 13 - The DC ENGAGE INTLK is the power source for several
interlocks and therefore a requirement for unlock and hold
logic.
(n) Item 14 - During an approach, if dual in CMD is desired, the
second A/P must be in CMD prior to a radio altitude of 800
feet.
(o) Item 15 - FCC DC is the primary power source for the FCC. The
power input and power supply are monitored.
(p) Item 16 - The 1800 Hz power must be valid.
(q) Item 17 - The power UP test checks the CPU by inserting a
signal to each of the two CPUs and comparing the outputs.
After the CPUs are checked, autoland and GA circuits are
checked. Both CPUs are used to process the signals and the
outputs compared. Likewise, a similar check is made of the
dual-channel monitors. There are two sets of dual-channel
monitors. These are exercised at power up by inserting BITE
signals and the results compared.
(r) Item 18 - The continuous monitor checks the operation of the
flight control computer; checks are made on ROM, program
memory, RAM read/write operation, direct memory access (DMA)
controller, D/A - A/D, program flow (TICKET) and heartbeat.
The CPU 1 and 2 are also monitored by a continuous background
BIT process. The power up stimilus test (STIM) is monitored to
assure that test signals are not present during normal
operation.
(s) Item 19 - The A/P continuous monitor only checks the actuator
position transducer to assure that an open circuit does not
exist. The neutral shift sensor is monitored for
reasonableness. The NSS is deemed failed if the voltage
changes greater than 10% of the full scale value per second.
Actuator command is monitored by comparing command against
response.
(t) Item 20 - A force applied on the control wheel inhibits A/P
engagement. A 3-pound force is set as the threshold.
(u) Item 21 - A force applied on the control column inhibits A/P
engagement. A 5-pound force is set as the threshold.
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