MAY 2015 Chapter 29 Hydraulics Page 29.1
CHAPTER 29
HYDRAULICS
29-00 Description
WARNING
Except as instructed in this manual, service on the hydraulic
system is limited to component removal and replacement.
CAUTION
Cleanliness of hydraulic fluid is vital to proper system
operation. Use only clean fluid from sealed containers and
avoid contamination from dirty funnels, tubing, etc. Use LPS
PreSolve to clean hydraulic parts. Do not use alcohol.
Hydraulically boosted main rotor flight controls eliminate cyclic and collective feedback forces.
The hydraulic system consists of a pump, three servos, a reservoir, and interconnecting lines.
Normal operating pressure is 450 to 500 psi. The pump is mounted on and driven by the
main rotor gearbox. A servo is connected to each of the three push-pull tubes that support
the main rotor swashplate. The reservoir is mounted to the aft end of the main rotor gearbox
and includes a filter, pressure relief valve, and pilot-controlled pressure shut-off valve.
A sight glass for pre-flight fluid level checks is incorporated in the reservoir and accessible
via a left side cowl door. A vented filler cap is located on top of the reservoir.
The pressure shut-off valve is solenoid-actuated and controlled by the hydraulic switch on
the pilot's cyclic. The switch should be left on during helicopter shutdown and start up
except during the hydraulic system check.
Electrical power is required to turn off hydraulics. Pulling HYD circuit breaker will NOT turn
off hydraulics but will disable hydraulic switch.
29-10 Hydraulic Pump
A. Removal
1. Remove tailcone cowling per § 53-23.
2. For helicopters with air conditioning:
a. Loosen hardware securing G777-1 compressor assembly to G781-1 arm weldment.
CAUTION
Do not use refrigerant hose assemblies or fittings to rotate
compressor. Do not rotate compressor further than necessary,
to avoid damaging system wiring and refrigerant hoses or fittings.
b. Rotate compressor down and inboard as required to disengage B173-5 v-belt from
pulleys.
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