2.9 LANDING GEAR.
The main landing gear (fig 2-2) supports the helicopter
during ground operation (taxiing, take-off, and towing).
The landing gear system is a three-point system consist-
ing of the main landing gear, tail landing gear, and main
landing gear brake system. The landing gear system pro-
vides for ease of maneuvering when taxiing and towing,
has shock struts to absorb normal and high impact land-
ings, and kneels to facilitate transport of the helicopter.
2.9.1 Main Landing Gear.
Each main landing gear
support consists of a trailing arm and a nitrogen/oil shock
strut. The trailing arms transfer the helicopter landing and
static loads to the airframe, and the shock struts absorb
vertical loads. The upper ends of the left and right trailing
arms attach to a cross tube which passes through the fu-
selage and is supported by fuselage-anchored pivot bear-
ings. The upper ends of the shock struts are attached to
mounts on the fuselage structure. In addition to its normal
energy-absorbing function, each shock strut has a one-
time high impact absorbing feature: shear rings are
sheared and a rupture disk bursts causing a controlled
collapse of the strut.
2.9.2 Tail Landing Gear.
The tail landing gear consists
of two trailing arms, nitrogen/oil shock strut, fork, axle, and
wheel. The shock strut has an impact-absorbing capability
similar to that of the main landing gear shock strut. The tail
wheel is 360 free swiveling for taxiing and ground han-
dling. The tail landing gear system incorporates a spring-
loaded tail wheel lock. However, the tail landing gear is hy-
draulically unlocked from the pilot crew station or
manually unlocked by a ground crewmember using a han-
dle attached to the actuator. The tail wheel lock system is
actuated by hydraulic pressure from the utility hydraulic
system. Pressure is routed to the actuator through a con-
trol valve located in the tail boom. The valve is controlled
by the tail wheel switch (fig 2-6) at the pilot station. When
the tail wheel switch is placed in the UNLOCK position,
pressure is applied to the actuator to retract the lock pin. A
proximity switch will cause the advisory light above the
switch to illuminate. When the tail wheel LOCK/UNLOCK
switch is placed in the LOCK position, a valve shuts off hy-
draulic pressure and opens the line to the actuator. This
relieves the pressure on the lock. Spring force will then
move the lock pin to the lock position. If the tail wheel is
unlocked manually, it can be locked from the pilot crew
station by placing the tail wheel switch in the UNLOCK
position, then returning the switch to the LOCK position.
The tail wheel shall be locked to:
a. Absorb rotor torque reaction during rotor brake op-
b. Prevent shimmy during rolling takeoffs and land-
c. Prevent swivel during ground operation in high
d. Prevent swivel during operation on slopes.
Tail Wheel Lock Panel
2.9.3 Landing Gear Brakes.
It is necessary to maintain pressure on the
brake until the PARK BRAKE handle is
pulled out to lock the parking brakes. If the
PARK BRAKE handle is pulled out without
pressure applied to the brake pedals, the
PARK BRAKE handle may remain out and
the brakes will not be set.
The brake system affects only the main landing gear
wheels. The main landing gear system consists of two in-
dependent hydromechanical systems, one left and one
right. Braking action is initiated from either crew station by
applying foot pressure at the top portion of the directional
control pedals. This activates a master cylinder attached
to each brake pedal (fig 2-7 and 2-8). The master cylin-
ders pressurize hydraulic fluid in the master cylinder sys-
tem components. This pressure is