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mechanically retracted. With weight on the nose gear, placing the LAUNCH BAR switch to EXTEND
energizes the launch bar control valve and routes HYD 2A pressure to unlock, lower, and hold down the
launch bar. The green L BAR advisory light indicates that the launch bar has been extended.
With the launch bar extended, returning the LAUNCH BAR switch to RETRACT deenergizes the
launch bar control valve, isolates HYD 2A pressure, and allows dual retract springs to mechanically
return the launch bar to the up and locked position. A launch bar proximity switch is energized when
the launch bar is fully retracted.
When the launch bar is fully extended it is held against the deck by HYD 2A pressure. Deck load
springs allow vertical movement of the launch bar during taxi over the catapult shuttle. When the
aircraft is placed in tension on the catapult, the launch bar is held captive in the extended position by
the shuttle. Once in tension, the LAUNCH BAR switch should be placed to RETRACT in order to
remove HYD 2A pressure from the launch bar. When the LAUNCH BAR switch is placed to
RETRACT, the green L BAR light should go out.
Failure to place the LAUNCH BAR switch to RETRACT prior to
catapult launch may result in launch bar hydraulic seal failure and
possible loss of HYD 2A.
At the end of the catapult stroke, launch bar/shuttle separation occurs and allows the retract springs
to return the launch bar to the up and locked position. When engaged, the launch bar uplock prevents
the launch bar from dropping to the deck due to g-loads during landing.
If the launch bar does not return to the up and locked position after catapult launch (launch bar
proximity switch not energized), the nose landing gear cannot be retracted. In this case, placing the
LDG GEAR handle UP will raise the main landing gear and leave the nose landing gear extended.
2.7.4.1 LAUNCH BAR Switch. The LAUNCH BAR switch, located on the lower left main instrument
panel in the front cockpit, is used to control the position of the aircraft's launch bar. The switch is
spring loaded to the RETRACT position and is electrically held in the EXTEND position only if
weight is on the nose gear.
RETRACT Launch bar control valve deenergized. Launch bar up.
EXTEND Launch bar control valve energized. Launch bar unlocked and extended by HYD
2A pressure. Green L BAR advisory light on.
2.7.4.2 LB Circuit Breaker. The LB circuit breaker is located on the left-hand circuit breaker panel
above the left console. The LB circuit breaker provides a secondary means to raise the launch bar
A1-F18EA-NFM-000
I-2-53 ORIGINAL
following a launch bar malfunction. When pulled, the circuit breaker manually deenergizes the launch
bar control valve, removing HYD 2A pressure and allowing the retract springs to raise the launch bar.
Typically, this action would be required only if (1) the LAUNCH BAR switch failed in the EXTEND
position with weight on the nose gear or (2) the nose gear failed WonW after launch and the pilot failed
to place the LAUNCH BAR switch to RETRACT.
2.7.4.3 L BAR Warning/Advisory Lights. Two L BAR lights, one green and one red, are located on
the left warning, caution, and advisory lights panel. Both lights are controlled by the landing gear
control unit (LGCU), based on inputs from the LAUNCH BAR switch, the launch bar proximity
switch, and various landing gear proximity switches.
The green L BAR advisory light is used to indicate that the launch bar has been extended. The
LGCU illuminates the green L BAR light when all of the following conditions are met: weight on the
nose gear, the LAUNCH BAR switch in EXTEND, the launch bar not up (launch bar proximity switch
not energized), and the red L BAR warning light not on.
The red L BAR warning light is used to indicate failure of the launch bar to retract after catapult
launch or a failure in the launch bar control system (proximity switch failure). The LGCU illuminates
the red L BAR light when one of the following sets of conditions are met:
1. Launch bar not up and weight off the left main gear.
2. Launch bar not up and left main gear not down.
3. LAUNCH BAR switch in EXTEND and weight off the left main gear.
4. LAUNCH BAR switch in EXTEND and left main gear not down.
The first set of conditions is the primary L BAR warning, e.g., the launch bar does not retract fully
after catapult launch. The other three sets of conditions provide a backup L BAR warning if one or
more of the proximity switches which control launch bar functioning fail.
2.7.5 Arresting Hook System. The arresting hook is always down-loaded by a nitrogen-charged
accumulator (arresting hook snubber) contained in the arresting hook retract actuator. Arresting hook
extension is therefore accomplished by mechanically releasing the arresting hook uplatch mechanism
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NATOPS Flight Manual 飞行手册 1(56)
