MACH TRIM ACTUATOR - ADJUSTMENT/TEST
1. Mach Trim Actuator Test
A. General
(1) The following test assumes the elevator is rigged; if not, refer to Chapter 27, Elevator and Tab Control.
B. Prepare to Test Mach Trim Actuator
(1)
Verify stabilizer and elevator surfaces are free to move.
(2)
Pressurize hydraulic systems A and B. Refer to 29-11-0, Hydraulic System A -Maintenance Practices and 29-12-0, Hydraulic System B - Maintenance Practices.
(3)
Ensure ground power is applied and check that mach trim and air data No. 1 circuit breakers on load control center P6 (or P18 on airplanes with SP177 autopilot system) are closed.
(4)
Position stabilizer trim to three units.
C. Test Mach Trim Actuator
(1)
Jiggle captain's control column to ensure control system is centered.
(2)
Check that mach trim coupler self-test switch is off and press reset button for 10 seconds. Note elevator trailing edge position with reference to the index plate.
(3)
Position self-test switch to 1 and press reset button for 10 seconds. Check that elevator trailing edge moved up 1.5 (+ 0.4) inches from position noted in step 2.
(4)
Position self-test switch to OFF and press reset button for 10 seconds. Check that elevator trailing edge returns to position noted in step 2.
(5)
If no longer required, remove electrical power from the airplane.
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MACH TRIM COUPLER - REMOVAL/INSTALLATION
1. General
A. The mach trim coupler is located in the E1 equipment rack in the electrical and electronics compartment. The coupler is installed with a knurled nut on swiveled bolts.
2. Remove Coupler
A. Open the mach trim AC and DC circuit breakers on P6 panel (or P18 panel on airplanes with SP177 autopilot system).
B. Remove the coupler (Ref 20-10-111, Electrical/Electronic Black Box - Maintenance Practices).
3. Install Coupler
A. Install the coupler (Ref 20-10-111, Electrical/Electronic Black Box - Maintenance Practices).
B. Close the mach trim AC and DC circuit breakers.
C. Do the mach trim self-test (Ref 22-21-00, Mach Trim System - Adjustment/Test).
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MACH TRIM FLAP SWITCH - REMOVAL/INSTALLATION
1. General
A. Five switches are located on the flap control unit. The mach trim flap switch is mounted on the aft (inner) portion of the unit. (See figure 401.) The five switch leads make a single wire bundle and must be separated during the mach trim switch removal and retied when the new switch is installed.
2. Remove Mach Trim Flap Switch
A. Remove switch cover from flap control unit. (See figure 401.)
B. Separate wire bundle connector from receptacle.
C. Remove wire bundle support clamps and bundle ties.
D. Separate mach trim flap switch leads from bundle and disconnect from connector.
E. Extract pin to release roller guide.
F. Remove retaining nut from limit switch and remove switch from control unit.
G. Replace nut, roller guide, and pin on switch.
3. Install Mach Trim Flap Switch
A. Remove pin, roller guide, and one retaining nut from switch. (See figure 401.)
B. Position switch in flap control unit and install retaining nut and roller guide. Install pin to secure roller guide.
C. Install switch leads in connector and connect to receptacle.
D. Replace wire bundle ties.
E. Install wire bundle support clamps.
F. Adjust and test mach trim switch. See Mach Trim Flap Switch - Adjustment/Test.
G. Ensure that switch retaining nuts are lockwired.
H. Install switch cover on flap control unit.
May 15/68 22-21-31 Page 401 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
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