of elements required for a system varies according to
GUN DRIVE AND DRUM DRIVE SYSTEMS
The M61A1 gun and the ammunition handling
system is simultaneously driven by a hydraulic drive
unit run by the aircrafts hydraulic 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. This is done by actuating a manual
control on the hydraulic drive unit when the aircrafts
hydraulic system is operating.
GUN GAS PURGE SYSTEM
The M61A1 gun is internally mounted in the
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 rounds
may cook-off due to excessive barrel temperatures. Gun
REVIEW NUMBER 3 ANSWERS TO QUESTIONS Q1. THROUGH Q8.
The major parts of the drum unit assembly are the drum unit, entrance cover, exit
cover, and scoop disk.
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 drum helix.
A spring-loaded timing pin on the entrance cover is used to index the drum for
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
The adapter assembly of the transfer unit and adapter assembly interfaces with
the linkless ammunition loading system (LALS).