Flight Control System Operation Electrical


TTP
B1-----
ATA27A
Cessna 172
B2-L3

                         
Flap- control system has an electric motor and transmission assembly, drive pulleys, push-pull rods, cables, and a follow-up control. Power from the motor and the transmission assembly goes to the flaps by a system of drive pulleys, cables, and push-pull rods. 
Electrical power to the motor is controlled by two MSW mounted on a floating arm assembly, a cam lever, and a follow-up control. As the flap control lever moves to the necessary flap setting, the attached cam activates one of the microswitches, and that activates the flap motor. As the flaps move to the necessary position, the floating arm is turned by the follow-up control until the active microswitch clears the cam. The circuit breaks and the motor stops.  
To move the flap in the opposite direction, the control lever is moved in the opposite direction. This causes the cam to activate the second microswitch, which changes the direction of the flap motor. The follow-up control moves the cam until it is clear of the second switch, which stops the flap motor. Limit switches at the flap actuator assembly control flap travel as the flaps get to the full UP or DOWN position.
Flap follow up and indicating system consists of a sheathed cable assembly, pointers and micro switches. One end of the cable is attached to the flap operating switch operating arm. The other end is clamped to the flap direct cable, above the headliner in the rear cabin area. Motion of the flap cable is transmitted through the follow up control to the pointer, attached to the switch mounting arm. 
Pointer moves along a scale as the flaps are extended or retracted. When the motion of the switch mounting arm with the attached operating switches positions the "active" operating switch to clear the cam on flap lever, flap motor circuit is broken and flaps stop at selected position.
Trim system -  elevator trim tab on the right elevator is controlled by a trim wheel in the pedestal. Movement to operate the tab goes from the trim control wheel with chains, cables, and an actuator. A mechanical pointer adjacent to the trim wheel shows the tab position. A nose up setting on the trim wheel gives a tab down position.

PTP
Cessna
172
B1
LOC
FOT
SGH
R/I
MEL

B2
LOC
FOT

R/I

TS

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