The blade fold cylinder is found inside the sleeve
As the blade starts to spread, the lock valve solenoid is
spindle of the No. 2 blade. See figure 17-13. It
de-energized, releasing fluid in the rotary-wing head.
connects to sector gears, which cause the folding
When the blade is completely spread, hydraulic
actions. When the No. 2 blade reaches a certain angle,
fluid is sent to the blade lock cylinder, engaging the
a microswitch turns on the blade folded light in the
blade lockpin. Engagement and locking of the blade
cockpit. The lock valve traps hydraulic fluid in the
lockpin causes the internal sequencing mechanisms to
rotary-wing head to keep the damper-positioners in the
direct pressure to the control lock cylinder. The control
autorotative position. It also keeps the No. 2 blade in
lock cylinder, in turn, locks the controls. The spread
the folded position.
sequence is completed. The FOLD PWR, BLADE
With the fold sequence completed, the SAFETY
SPREAD, and SAFETY VALVE OPEN warning and
VALVE OPEN, the FOLD PWR ON, the No. 1
indicating lights should be lit.
BLADE POS, the CONT LOCKPIN ADV, and the
BLADES FOLDED warning and indicating lights are
Blade Folding System Components
lit.
Hydraulic components of the blade folding system
NOTE: You may have to move the cyclic control
are conventional type, solenoid-operated selector
stick around the neutral position to engage the control
valves, check valves, pressure reducers and snubber,
lockpin. If excessive movement of the cyclic stick is
sequence valves, and actuating cylinders. Of special
necessary, troubleshoot the system for possible
interest are the safety valve, the blade positioner drive
maladjustment.
unit, the rotor coupling, the control lock cylinder, and
Blade Spreading Operations
the blade fold accumulator.
S A F E T Y VA LV E . -- T h e s a f e t y va l ve i s a
The spreading operation requires the same
two-position, motor-operated selector valve. The
conditions as the fold operation. The primary
purpose of the unit is to prevent hydraulic pressure
exception is that the blade fold switch is in the
from entering the blade fold system during flight. The
SPREAD position. Pressure is sent through the
motor provides a camming action to move the poppet
m o t o r- o p e r a t e d s a f e t y va l ve a n d t h r o u g h t h e
valve within the selector valve. With the rotor stopped,
positioning unit pressure reducers. Pressure is sent to
electrical interlocks allow the safety valve to send fluid
the blade positioner drive unit for rotor brake disc
to the blade folding system. This action occurs when
disengagement and the engagement of the rotor brake.
the safety valve switch is placed in the OPEN position.
With the rotor brake on and the blade fold valve
In the CLOSED position, pressure is blocked at the
energized, 3,000-psi hydraulic fluid is sent through the
pressure port. The system vents through the lock
rotor coupling. From the coupling, pressure is sent to
valve. The venting eliminates the possibility of
the damper-positioners. The damper-positioners drive
damage to the system by thermal expansion of the
the blades against their autorotative stops. Pressure is
hydraulic fluid. The safety valve will not close if the
then sent to the blade fold cylinder. The blade fold
blade spread interlock relay malfunctions. The safety
cylinder operates the gear sector and spreads the blade.
valve will not close if the blades are folded. The safety
valve motor opens a limit switch. The switch cuts
electrical power to the motor when the safety valve
reaches the fully open position.
BLADE POSITIONER DRIVE UNIT.--The
drive unit is found on the upper surface of the main
gearbox input cover. It consists of a gear train, a
sequence valve, a filler plug, a sight gauge, and a
hydraulic motor. The gear train rotates because of the
hydraulic motor. The gear train turns the rotary-wing
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
Figure 17-13.--Blade fold cylinder.
17-18
