Hydraulic motors are used to convert hydraulic
instructions. This problem is usually resolved by
pressure into rotary mechanical motion. The type of
replacement of the actuator. After the repairs are
hydraulic motor used in naval aircraft is similar in
made, you must test the actuator to verify its
general design and construction to the piston-type
performance.
pumps. The difference in the operation of a hydraulic
Q11-1. What unit transforms hydraulic fluid pressure
motor and a hydraulic pump is as follows: In the
into mechanical force, which performs work
operation of a pump, when the drive shaft is rotated,
by moving some mechanism?
fluid is drawn into one port and forced out the other
under pressure. This procedure is reversed in a
Q11-2. Aircraft actuating cylinders are used when
hydraulic motor. By directing fluid already under
which of the following mechanism movements
pressure into one of the ports, pressure will force the
are required?
shaft to rotate. Fluid will then pass out the other port,
Q11-3. If hydraulic pressure is used to move a
and back to return. The rotary mechanical force
single-acting actuating cylinder in only one
provided by the motor can be used to drive a gearbox,
direction, what force is used to move it in the
torque tube, or jackscrew.
opposite direction?
Hydraulic motors are commonly used to operate
Q11-4. T h e o p e r a t i o n o f a s i n g l e - a c t i n g ,
the wing flaps and radar equipment. Hydraulic motors
spring-loaded, piston-type actuating cylinder
may be operated in either direction of rotation, with the
is normally controlled by what component?
rotation being controlled by the direction of flow to the
valve plate ports. The direction of rotation may be
Q11-5. Most piston-type actuating cylinders are of
instantly reversed without damaging the motor. A
what type?
selector valve controls the direction of flow.
Q11-6. An unbalanced, double-acting, piston-type
A typical hydraulic motor is shown in figure 11-6.
actuating cylinder uses a directional control
This is a nine-cylinder, fixed-stroke motor. It is
valve capable of directing fluid in what total
self-lubricating and requires no line maintenance other
number of ways?
than periodic visual inspection for leakage. The motor
Q11-7. When the cylinder is in the down and locked
is equipped with a stub tooth spline, suitable for
position, the locking ball bearings are held in
engagement into the mechanical linkage of the unit to
the locking position by what means?
be actuated on the aircraft.
Q11-8. To equalize the displacement of fluid on either
Any shop maintenance that must be performed on
side of the piston, a double-action, finger-lock
a hydraulic motor should be done in accordance with
actuator incorporates what component?
instructions contained in the applicable Overhaul
Q11-9. During normal extension of a landing gear
Instruction Manual (03 series).
finger-lock actuator, what forces move the
Q11-13. What type of motor converts hydraulic
piston over the fingers?
pressure into rotary mechanical motion?
Q11-10. In a power-operated flight control system, all
Q11-14. Hydraulic motors are commonly used to
the force necessary for deflecting the control
operate what aircraft equipment?
surface is supplied by what type of pressure?
Q11-11. A tandem-type, control surface, actuating
VALVES
cylinder uses a synchronizing rod for what
purpose?
LEARNING OBJECTIVE: Identify typical
Q11-12. In the maintenance of actuating cylinders,
valves in a basic actuating system.
w h a t i s t h e m o s t c o m m o n t ro u b l e
encountered?
A valve is defined as a device that provides control
of the flow or pressure in a hydraulic system. There are
HYDRAULIC MOTORS
many types of valves, such as selector valves, check
valves, sequence valves, shuttle valves, restrictor
valves, pressure-reducing valves, and hydraulic fuses.
LEARNING OBJECTIVE: Identify typical
While the basic function for each type of valve is
hydraulic motors.
11-7
