During system operation, the conveyor receives rounds
of ammunition from the exit unit and delivers them
through the feed chute to the transfer unit. The
conveyor also receives expended cases and unfired
rounds from the transfer unit and transports them
through the return chute to the entrance unit. After
receipt by the entrance unit, the expended cases and
unfired rounds are removed from the conveyor
elements and stored in the ammunition drum. The
empty conveyor passes from the entrance unit to the
exit unit through the bypass chute. Tabs on the
conveyor elements, which engage guides in the chutes,
exit unit, entrance unit, adapter assembly, and transfer
unit, maintain positive control of the conveyor
elements. The total number of elements required for a
system varies according to aircraft application.
GUN DRIVE AND DRUM DRIVE SYSTEMS
A hydraulic drive unit run by the aircrafts
hydraulic system simultaneously drives the M61A1
gun and the ammunition handling system. The
hydraulic pressure is supplied through a hydraulic fluid
manifold electrically controlled by a dual-rate solenoid
valve. This solenoid valve is controlled from the
cockpit through the gun control unit (GCU), which
results in the gun firing at 6,000 (GUN HIGH) or 4,000
(GUN LOW) rounds per minute. Attached to the
hydraulic drive unit is a mechanical drive unit that
consists of a gear train with one input shaft (from the
hydraulic drive unit) and, depending upon the type of
aircraft, one or two output shafts.
F-14 aircraft. The F-14 aircraft uses a mechanical
drive unit with two output shafts. The mechanical drive
unit causes a telescoping shaft to drive the gun and the
drum unit assembly.
F/A-18 aircraft. The F/A-18 aircraft uses a
mechanical drive unit with one output shaft. Because
the ammunition drum is near the mechanical drive unit,
a gear on the output shaft of the mechanical drive unit
meshes directly with the drum drive. A two-piece
telescoping shaft transmits power from the same output
shaft of the mechanical drive unit to the gun drive. This,
in turn, drives the gun rotor.
Both aircraft have provisions to manually rotate the
gun system by using a manual hand crank. During
ground maintenance, the gun system may be rotated
hydraulically. Actuating a manual control on the
hydraulic drive unit when the aircrafts hydraulic
system is operating does this.
REVIEW NUMBER 3 ANSWERS
The major parts of the drum unit assembly are
the drum unit, entrance cover, exit cover, and
The inner drum helix of the drum assembly
looks like the threads of a screw and produces
a screwing-type motion, causing rounds to
slide along partitions from one end to the
other end of the outer drum.
The purpose of the retainer gear and steel
ball bearings contained in the entrance cover
is to support the scoop disks and the inner
A spring-loaded timing pin on the entrance
installation of the exit unit.
The two sets of sprocket spur gears located on
the scoop disk mesh with the retainer gear in
the entrance and exit covers that provide
rotating support for the inner drum helix.
The last round switch in the exit unit prevents
expended rounds from being fed into the gun
and jamming it.
The sprocket assemblies in the entrance unit
remove live rounds or expended cases from
the conveyor elements and place them in the
entrance cover retainer partitions.
The adapter assembly of the transfer unit and
adapter assembly interfaces with the linkless
ammunition loading system (LALS).
GUN GAS PURGE SYSTEM
The M61A1 gun is internally mounted in the
aircraft's fuselage. When the gun is fired, the
temperature of the gun barrels increases rapidly, and the
gun compartment is filled with gun gas from the fired
rounds. If the barrels are not properly cooled, the
temperatures. Gun gas, when confined to an enclosed
area such as a gun compartment, is highly explosive.
The gun gas purge system cools the barrels and purges
gas from the compartment during gun firing operations.
The gun gas purge system in the F-14 aircraft uses
cold air from the refrigeration system to cool and purge
residual gun gases from the ammunition drum and gun
compartment. The subsystem, activated when gun
firing is initiated, remains active for a 30-second period