TM 1-1510-223-10
The landing gear system utilizes folding braces
called drag legs, that lock into place when the gear is
fully
extended
The
nose
landing
gear
actuator
incorporates an internal down lock to hold the gear in
the fully extended position. However, the two main
landing gear are held in the fully extended position by
mechanical hook and pin locks. The landing gear is
held in the up position by hydraulic pressure. The
pressure is controlled by the power pack pressure switch
and an accumulator that is precharged with nitrogen to
800 50 psi. Gear doors are opened and closed through
a mechanical linkage connected to the landing gear.
The nose wheel steering mechanism is automatically
centered and the rudder pedals relieved of the steering
load when the landing gear is retracted. Air-oil type
shock struts, filled with compressed nitrogen and
hydraulic fluid, are incorporated with the landing gear.
a.
Landing Gear Control Switch. Landing gear
system operation is controlled by a manually actuated
wheel-shaped switch placarded LDG GEAR CONTR -
UP - DN, on the pilot's subpanel (fig. 2-6). The control
switch and associated relay circuits are protected by a 2-
ampere circuit breaker, placarded LANDING GEAR
CONTROL located on the overhead circuit breaker
panel (fig. 2-7).
b.
Landing Gear Down Position Indicator Lights.
Visual indication of the landing gear position is provided
by three individual green GEAR DOWN position
indicator lights located on the pilot's subpanel. Testing
of the indicator lights is accomplished by pressing the
annunciator test switch. The circuit is protected by a 5-
ampere circuit breaker, placarded LANDING GEAR IND,
on the over-head circuit breaker panel (fig. 2-7).
c.
Landing Gear Position Warning Lights. Two
red parallel-wired indicator lights, located in the LDG
GEAR CONTROL switch handle, illuminate to show that
the gear is in transit or unlocked. The red indicator
lights in the handle also illuminate when the landing
gear warning horn is actuated. Both red indicator lights
indicate the same warning conditions, but two are
provided for a fail-safe indication in case one bulb bums
out The circuit is protected by a 5-ampere circuit
breaker, placarded LANDING GEAR IND, on the
overhead circuit breaker panel (fig. 2-7).
d.
Landing Gear Warning Indicator Light Test
Switch. A test switch, placarded HDL LT TEST, is
located in the pilot's subpanel (fig. 2-6). Failure of the
landing gear handle to illuminate red when this test
switch is pressed, indicates two defective bulbs or a
circuit fault The circuit is protected by a 5-ampere circuit
breaker, placarded LANDING GEAR HORN, on the
overhead circuit breaker panel (fig. 2-7).
e.
Landing Gear Warning System. The landing
gear warning system is provided to warn the pilot that
the landing gear is not down and locked during specific
flight
regimes.
Various
warning
modes
result,
depending upon the position of the flaps.
At airspeeds above 140 KIAS with flaps in the UP
or APPROACH position and either or both POWER
levers retarded below approximately 84% N1, the
landing gear switch handle annunciator will illuminate.
The horn is automatically silenced by an altitude sensing
switch, provided to silence the landing gear warning
horn when above 12,500 feet. This prevents the horn
from sounding above 12,500 feet when either POWER
lever is pulled back, provided the flaps are at the
approach position or above.
At airspeeds below 140 KIAS with flaps in the UP
or APPROACH positions with either or both POWER
levers retarded below approximately 84% N1, the
warning horn will sound and the landing gear switch
handle indicator lights will illuminate. The horn can be
silenced by moving the WARNING HORN SILENCE
switch located adjacent to the landing gear switch
handle, to the up position. However, the annunciators in
the landing gear switch handle cannot be canceled. The
gear warning silence switch is a magnetically held
switch. Once actuated it will stay in the up position until
both POWER levers are advanced above 86% N1,
and/or airspeed increases above approximately 153
KIAS.
In either case (airspeeds above or below 140
KIAS) the landing gear warning system will be rearmed
if both power levers are advanced above 86% N1.
With the landing gear retracted and flaps beyond
the APPROACH position, the warning horn and landing
gear switch handle annunciators will be activated
regardless of the power setting. The horn cannot be
silenced in this case, until either the landing gear is
lowered, or the flaps are retracted to the UP or
APPROACH position.
f.
Landing Gear Warning Horn Test Switch.
The warning horn and gear handle indicator lights can
be tested by placing the switch placarded STALL WARN
TEST - OFF - LDG GEAR WARN TEST to the LDG
GEAR WARN TEST position (fig. 26). The gear handle
warning lights will illuminate, and the warning horn will
sound. Releasing the LDG GEAR WARN TEST switch
to the OFF position will extinguish the gear handle
indicator lights, and silence the warning horn. The
landing gear warning horn circuit is protected by a 5-
ampere circuit breaker, placarded LANDING GEAR
HORN, located on the overhead circuit breaker panel
(fig. 2-7).
g.
Landing Gear Safety Switches. A safety
switch on each main landing gear shock strut controls
the operation of various aircraft systems that function
only during flight or only during ground operation.
These switches are mechanically actuated whenever the
main landing gear
2-14
