gear extension or retraction is normally accomplished in
6 to 7 seconds. Voltage to the power pack is terminated
after the fully extended or retracted position is reached.
If electrical power has not terminated within 14 seconds,
a relay and 2-ampere landing gear circuit breaker will
open, and electrical power to the system power pack will
The landing gear system utilizes folding braces,
called drag legs, that lock into place when the gear are
fully extended. The nose landing gear actuator
incorporates an internal down lock to hold the gear in the
fully extended position. The two main landing gear are
held in the fully extended position by mechanical hook
and pin locks. The landing gear are 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
centered and the rudder pedals relieved of the steering
load when the landing gear are retracted. Air-oil type
shock struts, filled with compressed nitrogen and
hydraulic fluid, are incorporated with the landing gear.
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. 2-8). 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. 2-9).
Landing Gear Down Position Indicator
Lights. Visual indication of 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 overhead circuit breaker
panel (fig. 2-9).
Landing Gear Position Warning Lights.
Two parallel-wired red 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 failsafe indication in case one bulb
burns out. The circuit is protected by a 5-ampere circuit
breaker, placarded LANDING GEAR IND, on the
overhead circuit breaker panel (fig. 2-9).
Landing Gear Warning Indicator Light Test
Switch. A test switch, placarded HDL LT TEST, is
located in the pilot's subpanel (fig. 2-8). When this test
switch is pressed, failure of the landing gear handle to
illuminate red 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. 2-9).
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% N,, 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 and 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 cancelled.
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% N, 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
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
LDC GEAR WARN TEST position (fig. 2-8). 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