overhead circuit breaker panel (fig. 2-6), and the
downlock switches. The power pack motor is protected
by a time delay module which senses operation voltage
through a 5-ampere circuit breaker. Both are located
beneath the aisleway floorboards, forward of the main
spar. Landing 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 be interrupted.
The landing gear system utilizes folding braces
called drag legs, that lock in 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.
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. 2-5). The control switch
and associated relay circuits are protected by a 2-
ampere circuit breaker, placarded LANDING GEAR
CONTROL located in the overhead circuit breaker panel
Landing Gear Down Position Annunciators.
Visual indication of the landing gear position is provided
by three, individual, green GEAR DOWN annunciators
located in the left subpanel. Testing of the annunciators
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. 2-6).
Annunciators. Two red parallel-wired annunciators,
located in the LDG GEAR CONTROL switch handle,
illuminate to show that the gear is in transit or unlocked.
The red annunciator in the handle also illuminates when
the landing gear warning horn is actuated. Both red
annunciators indicate the same warning conditions, but
two are provided for a fail-safe indication in the event
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. 2-6).
Landing Gear Warning Annunciator Test
Switch. A test switch, placarded HDL LT TEST, is
located in the pilot's subpanel (fig. 2-5). 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. 2-6).
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 with either or both power
levers retarded below approximately 84% N1, the
warning horn will sound and the landing gear switch
handle annunciators will illuminate. The horn can be
silenced by actuating the GEAR WARN 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 magneticlly 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