a. Landing Gear Down Position-Indicator
Lights. Landing gear down position is indicated by
three green lights on the left subpanel, placarded
GEAR DOWN. These lights may be checked by
operating 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. 2-26).
b. Landing Gear Position Warning Lights.
Two red bulbs, wired in parallel and activated by
microswitches independent of the GEAR DOWN
position indicator lights, are positioned inside the
clear plastic grip on the landing gear control switch.
These lights illuminate whenever the landing gear
switch is in either the UP or DN position and the
gear is in transit. Both bulbs will also illuminate
should either or both power levers be retarded below
approximately 79 to 81% N1 when the landing gear
is not down and locked. To turn the switch lights
OFF during single-engine operation, the power lever
for the inoperative engine must be advanced to a
position which is higher than the setting of the warn-
ing horn microswitch. Extending the landing gear
will also turn the lights off. Both red lights 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. 2-26).
c. Landing Gear Warning Light Test Button.
A test button, placarded HDL LT TEST, is located
on the left subpanel. Failure of the landing gear
switch to illuminate red, when this test button is
pressed, indicates two defective bulbs or a circuit
fault. The circuit is protected by a 5-ampere circuit
breaker, placarded LANDING GEAR RELAY
CONTROL, on the overhead circuit breaker panel
d. Landing Gear Warning Horn. When either
power lever is retarded below approximately 79 to
81 N, when the landing gear is not down and locked
or if the flaps are extended beyond 40% and the
landing gear is not down and locked, a warning horn
located in the overhead control panel will sound
intermittently. To prevent the warning horn from
sounding during long descents or an ILS approach,
a pressure differential Q switch is connected into
the copilots static line. The switch prevents the
warning horn from sounding until airspeed drops
below 140 KIAS. An altitude sensing switch is
installed in series with the 140 KIAS Q switch
which prevents the warning horn from sounding
after climbing through 12,500 feet MSL. The horn
will be engaged when the aircraft descends through
10,500 MSL. The warning horn circuit is protected
by a 5-ampere circuit breaker, placarded LANDING
GEAR WARN, on the overhead circuit breaker
panel (fig. 2-26).
e. Landing Gear Warning Horn Test Switch.
The landing gear warning horn may be tested by the
test switch on the right subpanel (fig. 2-6). The
switch, placarded STALL WARN TEST - OFF -
LDG GEAR WARN TEST, will sound the landing
gear warning horn and illuminate the landing gear
position warning lights when moved to the momen-
tary LDG GEAR WARN TEST position. The circuit
is protected by a 5-ampere circuit breaker, placarded
LANDING GEAR WARN, on the overhead circuit
breaker panel (fig. 2-26).
f. Landing Gear Safety Switches. A safety
switch on each main landing gear shock strut con-
trols 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 shock struts are
extended (normally after takeoff), or compressed
(normally after landing). The safety switch on the
right main landing gear strut activates the landing
gear control circuits, cabin pressurization circuits
and the flight hour meter flight time function on the
copilots clock when the strut is extended. This
switch also activates a down-lock hook, preventing
the landing gear from being raised while the aircraft
is on the ground. The hook, which unlocks automat-
ically after takeoff, can be manually overridden by
pressing down on the red button, placarded DN
LOCK REL located adjacent to the landing gear
switch. If the override is used and the landing gear
control switch is raised, power will be supplied to
the warning horn circuit and the horn will sound.
The safety switch on the left main landing gear strut
activates the left and right engine ambient air shut-
off valves when the strut is extended.
g. Landing Gear Alternate Engage Handle.
During manual landing gear extension, the landing
gear motor must be disengaged from the landing
gear drive mechanism. This is accomplished by a
manually-operated clutch disengage lever (fig. 2-7)
located adjacent to the landing gear alternate exten-
sion handle (fig. 2-7). To disengage the clutch, pull
the alternate engage handle up and turn clockwise.
To engage the clutch, turn the alternate engage han-
dle counterclockwise and release.