D. Test Mach Trim System
(1)
Test Indicator Lights
(a)
Open mach trim ac and dc circuit breakers.
(b)
Observe mach trim fail indicator light, located on P5 panel, the two MASTER CAUTION lights and FLT CONT master caution annunciator lights are illuminated.
(c)
With light switch positioned to DIM, observe mach trim fail indicator light is dim.
(d)
With light switch positioned to BRT, observe mach trim fail indicator light returns to bright.
(e)
With either master caution light depressed, observe both MASTER CAUTION light and FLT CONT master caution annunciator light extinguishes and observe mach trim light remains illuminated.
(f)
Momentarily depress FLT CONT master caution annunciator light and observe both MASTER CAUTION lights and FLT CONT master caution annunciator light illuminates.
(2)
Test Circuit Breakers, Warning Lights, and Mach Trim Cockpit Test Switch
(a)
Close air data computer-1 ac and 26 volt ac circuit breakers on load control center P18 and mach trim computer circuit breakers ac and dc on load control center P6 (or P18 on airplanes with SP177 autopilot system). Observe mach trim warning light is off.
(b)
Open mach trim dc circuit breaker. Observe mach trim warning light illuminates.
(c)
Close mach trim dc circuit breaker. Observe mach trim warning light extinguishes.
(d)
Open mach trim ac circuit breaker. Observe mach trim warning light illuminates.
(e)
Lower flaps to 1 unit. Observe mach trim warning light extinguishes.
(f)
Raise the flaps. Observe the mach trim warning light illuminates.
(g)
Close mach trim ac circuit breaker. Observe mach trim warning light extinguishes.
(h)
Open air data computer 115-volt ac circuit breaker. Observe mach trim warning light illuminates.
(i)
Close air data computer 115-volt ac circuit breaker, and observe mach trim warning light extinguishes.
(j)
Open air data computer 26-volt ac circuit breaker. Observe mach trim warning light illuminates.
(k)
Close air data computer 26-volt ac circuit breaker. Observe mach trim warning light extinguishes.
(l)
Move self-test switch, located on mach trim coupler, to position 1 and depress the reset button for 10 seconds. Observe mach trim warning light illuminates and coupler light remains off.
(m)
Return self-test switch to OFF. Observe mach trim coupler light and mach trim warning light illuminates.
(n)
Press reset button for 10 seconds. Observe coupler light and mach trim warning light extinguishes.
(o)
Depress and hold for at least 15 seconds the mach trim cockpit test switch which is on the overhead panel. Observe the mach trim fail light illuminates 4 seconds after depressing test switch and captain's column moves slightly aft.
NOTE: Mach trim fail light may flash on momentarily, and master caution light may come on when test switch is depressed. Observe steady illumination of mach trim fail light 4 seconds after test switch operation.
(p)
Release the test switch. Observe the column moves slightly forward and the light extinguishes after 10 seconds.
(3)
Test Self-Test Annunciation
(a) Operate mach trim self-test switch to each of five positions and return to off. Observe mach trim warning light illuminates for each position.
(4)
Test Mach Trim Self-Test
505
22-21-0 Page 502 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Oct 20/93
Step Action Observe
(a)
Self-test switch in Self-test meter reads in the RED
OFF position. range, and coupler light is extinguished.
(b)
Place self-test switch Self-test meter reads in the RED
to position 1. range and coupler light illuminates.
501
May 20/82 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 22-21-0 Page 503
Step(c) ActionDepress reset button for 10 seconds. Observe Coupler light extinguishes.
(d) Place self-test switch to position 2. Depress reset button for 10 seconds. Self-test meter reads in RED range and coupler light illuminates 4 to 7 seconds after switching from self-test position one.
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