29-30 Hydraulic Servos
A. Servo Removal
CAUTION
Do not pressurize hydraulic system while any hydraulic system
component is disconnected or removed.
1. Remove mast fairing per § 53-22. Remove tailcone cowling per § 53-23.
2. Refer to Figures 29-1 and 29-3. Perform the following measurements on all D212
hydraulic servo assemblies to be removed:
a. Measure and record dimension between D200-1 clevis hole center & top of servo
piston.
b. Apply cyclic and collective frictions. With collective full down and hydraulics
unpressurized, position cyclic stick so piston in servo to be removed is in its lowest
position. Measure and record dimension between top of servo piston and top of
cylinder assembly.
3. Remove hardware securing servo clevis to F121-3 push-pull tube’s lower rod end.
4. a. Forward Servo: Remove hardware securing servo to F121-5 push-pull tube’s upper
rod end. Remove hardware joining D200-2 scissors.
b. Aft Servo: Remove hardware securing C343-8 tube’s lower rod end to F339-1
jackshaft weldment.
5. Disconnect D205 hose assemblies from servo unions and tees. Cap and plug fittings.
6. Remove hardware securing servo to G201-1 frame weldment and remove servo.
7. Aft Servo: Measure and record center-to-center dimension between aft servo’s lower
rod end and C343-8 tube’s lower rod end. Loosen palnut and nut securing C343-8
tube to aft servo’s lower rod end and remove tube.
CAUTION
Do not remove tri-wing fastener; aft servo’s lower rod end must
remain attached to servo.
CAUTION
Dimension between clevis hole center and top of servo piston
must be 1.40 ± 0.03 inches; dimension between top of servo
piston and top of cylinder assembly must be 0.28 ± 0.03 inch;
dimension between C343-8 tube’s rod ends must be 4.00 ±
0.03 inches. If dimension(s) are not within required range,
perform main rotor rigging per § 18-40 after servo installation.
8. Remove clevis, scissor, D200-3 washer, unions, and tee fittings from servo, as
applicable.
9. Actuate servo piston by hand and drain as much hydraulic fluid from servo as possible.
Plug servo ports.
Page 29.6 Chapter 29 Hydraulics MAY 2015
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