29-30 Hydraulic Servos (continued)
B. Servo Installation
CAUTION
Do not pressurize hydraulic system while any hydraulic system
component is disconnected or removed.
CAUTION
Refer to Part A. 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) recorded during servo
removal were not within required range, or if dimension(s) are
unknown, adjust to correct dimensions in Part B steps 1 and 2,
proceed with servo installation thru step 10, then perform main
rotor rigging per § 18-40.
1. Refer to Figures 67-2 and 67-3B. Lightly coat D200-1 clevis threads with B270-21
protectant. Assemble clevis, palnut, nut, D200-3 washer (forward servo), and D200-
2 scissor (forward servo), and install assembly in D212 hydraulic servo assembly
piston. Adjust dimension between clevis hole center & top of servo piston to dimension
recorded during servo removal, then tighten jam nut and palnut finger tight.
2. Aft Servo: Lightly coat servo’s lower rod end threads with B270-21 protectant and
install C343-8 tube. Adjust tube on servo‘s rod end, and tube’s rod end, to the center-
to-center dimension (between rod ends) recorded during servo removal, and with rod
ends 90° to each other. Tighten jam nuts and palnuts finger tight.
CAUTION
Do not remove tri-wing fastener; aft servo’s lower rod end must
remain attached to servo.
3. Install hardware securing servo to G201-1 frame weldment. Standard torque fasteners
per § 20-32 and torque stripe per Figure 5-1.
4. Forward Servos: Install hardware joining scissors (scissor overlap direction not critical);
special torque nut to 25 in.-lb, special torque palnut to 5-10 in.-lb, and torque stripe
per Figure 5-1.
5. Using backup wrench, align clevis parallel with helicopter’s longitudinal axis, standard
torque jam nut and palnut per § 20-32, and torque stripe per Figure 5-1.
6. Install hardware securing servo clevis to F121-3 push-pull tube’s lower rod end.
Standard torque fastener per § 20-32 and torque stripe per Figure 5-1.
MAY 2015 Chapter 29 Hydraulics Page 29.7
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