is installed under each wing. Because aircraft are
different in size, shape, and construction, every landing
gear is specially designed. Although main landing gears
are designed differently, all main gear struts are attached
to strong members of the wings or fuselage so that the
landing shock is distributed throughout the main body
of the structure. The main gears are also equipped with
brakes that are used to shorten the landing roll of the
aircraft and to guide the aircraft during taxiing.
Nose Landing Gear
On aircraft with tricycle landing gear, the nose gear
is retracted either rearward or forward into the aircraft
fuselage. Generally, the nose gear consists of a single
shock strut with one or two wheels attached. On most
aircraft the nose gear has a steering mechanism for
taxiing the aircraft. The mechanism also acts as a
shimmy damper to prevent oscillation or shimmy of the
nosewheel. Since the nosewheel must be centered
before it can be retracted into the wheel well, a centering
device aligns the strut and wheel when the weight of the
aircraft is off the gear. Damping, steering, and centering
devices are discussed later in this chapter.
The landing gear systems on rotary-wing aircraft
come in several different designs. A helicopter may
have a nonretractable landing gear, such as that found
on the H-46 and H-60 helicopters, or it may have a
retractable type landing gear like that incorporated on
the H-3 and H-53 helicopters. Some helicopters have a
nose landing gear while others have a tail landing gear.
The H-53 has a retractable nose landing gear, but the
H-46 has the nonretractable type of nose landing gear.
The H-3 and H-60 helicopters use tail landing gears.
The tail landing gear on both these helicopters is
nonretractable. While both these helicopters have tail
landing gear, the H-3 can retract its main landing gear
while the H-60 has a nonretractable main landing gear.
As you can see, helicopter landing gear systems
come in several different configurations. The landing
gear systems on most of the helicopters used in the Navy
use wheel and brake assemblies. The components used
in the landing gear system of a helicopter are very
similar to those used in a fixed-wing aircraft landing
gear system. In helicopters that use retractable landing
gear systems, the components and means of actuation
are also similar in design to fixed-wing aircraft. For
discussion purposes, we will use the landing also system
of the H-60 helicopter. This helicopter uses a
nonretractable main and tail landing gear.
Main Landing Gear
The main landing gear system of the H-60
helicopter consists of nonretractable left and right single
wheel landing gear assemblies and the weight-
on-wheels system. Each main landing gear assembly is
composed of a shock strut, drag beam, axle, wheel, tire,
and wheel brake. The left main landing gear assembly
also includes a weight-on-wheels sensing switch,
The main landing gear supports the helicopter when
it is on the ground, and cushions the helicopter from
shock during landing. The weight-on-wheels switch
provides helicopter ground or
for various helicopter systems.
Tail Landing Gear
flight status indications
The H-60 tail landing gear system consists of a dual-
wheel landing gear, tail wheel lock system, and tail
The tail landing gear is a cantilever type with an
integral shock strut. The gear is capable of swiveling 360
degrees. It can be locked in the trail position by the tail
wheel lock system. A tail recovery assist, secure, and
traverse (RAST) probe is mounted on the tail gear.
LANDING GEAR SYSTEMS
Learning Objective: Identify the operational
and troubleshooting procedures for landing
Landing gear systems on naval aircraft, as stated
earlier, are similar in design. Most aircraft equipped
with the tricycle-type, retractable landing gear have two
systems of operation, normal and emergency.
The normal system of a typical landing gear
system is described because many components used in
different landing gear systems are similar. Figure 12-2
is a schematic that shows the fluid flow in the nose gear
up cycle. This system contains a selector valve, flow
regulators, priority valves, check valve, actuating
cylinders, and the necessary hydraulic tubing that routes
hydraulic fluid to and from the required components.