head by running the rotor brake disc. The hydraulic
disc motor operates only after the gear train engages
the teeth of the rotor brake disc. Pressure is cut off to
the blade rotation control valve and the motor by the
sequence valve. This action occurs when the gear
train has been operated to disengage the rotor brake
ROTOR COUPLING.The rotor coupling is
found at the bottom of the rotary-wing shaft. It serves
to transfer hydraulic fluid to the rotary-wing head for
blade folding. Figure 10-14 shows a cross-sectional
view of the coupling.
The coupling consists of a
spindle that revolves with the rotary-wing shaft. A
stationary housing connects to hydraulic lines of
blade folding components. Hydraulic fluid is sent
through the rotor coupling, and then through the lock
valve. Pressure is then sent to the manifold, to the
damper-positioner shuttle valve, and to the
damper-positioner sequence valves.
CONTROL LOCK CYLINDER.The control
lock cylinder is on the No. 2 blade horn assembly
rotary-wing head. During the fold cycle, the control
lock cylinder locks the flight controls. This occurs
only after the blade has been positioned. During the
spread cycle, it unlocks the controls. A microswitch
within the housing of the cylinder causes the CONT
LOCKPIN ADV advisory light in the cockpit to light.
In event of hydraulic malfunction, the control lockpin
may be operated manually. This is done by turning a
sector gear bolt on the aft end of the cylinder. The
sector bolt rotates gear teeth on the end of the
actuating piston shaft.
BLADE FOLD ACCUMULATOR.A blade
fold accumulator is found inside of the rotary-wing
sleeve of the No. 1 blade. It has a preload of 1,500-psi
nitrogen pressure to maintain hydraulic pressure in
the rotary-wing head. The pressure is necessary to
keep the damper-positioners extended and the blade
locked in the folded position. It serves to compensate
for expansion and contraction of the hydraulic fluid
because of temperature changes. It also dampens out
pressure surges during fold and spread cycles.
AUTOMATIC BLADE FOLDING SYSTEM
Maintenance of the blade fold system consists of
periodic inspection, lubrication, operational testing,
and troubleshooting. Allowable maintenance at the
organizational level includes alignment, adjustment,
and the removal and installation of components. Parts
Figure 10-14.Rotor coupling.
replacement and cure date kits are available for
intermediate-level repair of defective parts. Before
removal of any component, secure the blades to
prevent damage. Whenever any part of the system is
repaired or replaced, the electrical portion of the
system should be tested, as required by the MIM.
Operationally check the entire hydraulic portion of
the system to ensure proper sequence of operation.
The hydraulic testing procedures discussed in the
following paragraphs are used as an example. Always
consult your MIM for correct procedures.
Charge the air accumulator with 1,500 psi of
nitrogen, with the blades in the spread position.
Connect a source of external hydraulic power to the
utility, primary, and auxiliary hydraulic systems. Set
pressure to 3,000 psi at approximately 3 gallons per
minutes for the utility system. Set pressure to 1,500
psi for the primary and auxiliary servo hydraulic
systems. Position the ACCESSORY DRIVE switch
to ACCESS DR. The accessory drive light will light.
At the start of the testing, make sure that PRI SERVO
PRESS, AUX SERVO PRESS, ACCESSORY
DRIVE, ROTOR BRAKE ON, and CHECK BLADE
FOLD lights will light. The ACCESSORY DRIVE,
FLIGHT POS, BLADE SPREAD, EXT PWR ON,
PRI SERVO PRESS, and AUX SERVO PRESS lights
should be lit. Visually check to see that the lockpins
are disengaged. Manually rotate the rotary head until
the leading edge of the No. 1 blade is in the aft
position. Engage the rotor brake. The rotor brake
pressure gauge should read a minimum of 320 psi.
Check that the rotor brake light comes on. Place the
collective pitch stick in the full low position and the