objective, the gun can be operated in the air-to-ground
(A/G) or air-to-air (A/A) computer mode. There are two
A/G modes-continuously computed impact point
(CCIP) and manual (MAN). There are three A/A
modes-director, disturbed, and cage. The pilot can
select any one of the A/G or A/A modes while in flight.
The ammunition handling system holds a maximum
of 578 rounds of ammunition. A rounds limiter, located
in the gun compartment, can be preset to limit the total
number of rounds the pilot can fire. The rounds limiter
is used during training missions, and permits two or
three gunnery missions from one gun load-out.
For example, the rounds limiter is set at 200
rounds by ground maintenance personnel.
When the pilot has fired 200 rounds, the gun’s
electrical system automatically initiates the gun
clearing cycle. This prevents further firing until
the rounds limiter is manually reset by ground
maintenance personnel.
While in flight, the pilot has the option of selecting
unrestricted firing or presetting the number of rounds
per burst. If the pilot selects unrestricted firing, the gun
fires continuously as long as the trigger is depressed and
ammunition is available.
For example, if the pilot presets 50 rounds, the
gun fires a burst of 50 rounds each time the
trigger is pulled and released. A display panel
in the cockpit continuously indicates the
number of rounds remaining.
The clearing sector retainer assembly (fig. 6-14) is
used to manually clear the gun. When the manual
clearing handle is in the cleared position, a wire rope
assembly depresses the gun clearing sector assembly
against the gun housing. This directs the breech-bolt
assemblies into the clearing cam path when the gun is
manually rotated. The manual clearing handle is held
in the clearing position by a locking tab. For safety
reasons, the manual clearing handle should remain
in the cleared position until you are actually
performing gun-arming procedures. When the gun
access door is closed, you can determine the position of
the manual clearing handle by the position of the
indicator located on the door. If the indicator is flush
with the door surface, the manual clearing handle is in
the firing position. If the indicator protrudes from the
door surface, the manual clearing handle is in the cleared
position.
The entire gun system is handled as a single
palletized unit. This includes the M61A1 gun, drum unit
assembly, ammunition chutes, element chutes, and
hydraulic motor.
The system bolts directly to the
aircraft structure with four bolts, and does not require
any other boresighting or alignment. Other than minor
adjustments in the aircraft, all maintenance is performed
at the intermediate-maintenance level. The system is
removed from the aircraft as a unit by using
gun-handling adapters, a weapon skid or trailer, and an
Aero 14C bomb-hoisting unit. The bomb-hoisting unit
is used to raise or lower the gun system as it is being
removed or installed. A gun system hoist adapter,
designed to support the hoist boom, is attached to the
aircraft during the raising or lowering operation. A
gun-handling adapter, attached to a weapons skid or
trailer, supports the gun system after it is removed from
the aircraft.
For further information concerning the F/A- 18
M61A1 gun installation, you should refer to Description
and Principles of Operation, A1-F18AA-750-100;
Testing and Troubleshooting, A1-F18AA-750-200;
Maintenance, A1-F18AA-750-300; and System
Schematics, A1-F18AA-750-500.
A1.
A2.
A3.
A4.
REVIEW NUMBER 4 ANSWERS TO QUESTIONS Q1. THROUGH Q4.
The feed chute provides a path from the exit unit to the adapter assembly.
The return chute provides a path from the transfer unit to the entrance unit of the
drum.
The gun gas purge system cools the barrels and purges gas from the gun
compartment during gun-firing operations.
The gun gas purge systems of F/A-18 aircraft use engine bleed air and have
additional gas control provided by a hydraulically actuated, ram-air scavenge
door that opens automatically during gun-firing operation. This is not present in
the F-14 aircraft.
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