The MAU-91 fin consists of four folding drag
plates with links, a support flange, and a support tube.
An energy absorber, made of aluminum honeycomb
tubing, is located on the support tube between the
stationary collar and the sliding collar. The sliding
collar is driven against the energy absorber, causing it
to compress and deform. A channel located on the top
drag plate holds the fin release wire until it is pulled out
at bomb release. The drag plates are held in the closed
position by a release band that is secured by a fin
release wire pin located in the latch of the release band.
The band tabs fit into slots located near the end of each
drag plate. The band is securely attached to the bottom
drag plate by a stainless steel clamp, which prevents
damage from the band striking the aircraft after release.
Fin adapter ADU-320/B attaches the MAU-91 fins
to the Mk 83 bomb. The adapter is secured to the aft end
of the bomb by eight setscrews. The fin support flange
has eight teeth that mate to ears on the fin adapter. A
garter spring is forced into the gap between the flange
teeth and the adapter, making sure that the teeth fit
tightly against the ears. Two locking pins, which fit
through matching holes in the flange and adapter,
prevent rotation of the fin.
The MAU-91 fin assembly is shipped in a wooden
shipping and storage container. Included in the
container are eight suspension lugs, one spare garter
spring, and a spare locking pin.
Principles of Operation
There are three modes of delivery available for the
Snakeye fin assembly. They are retarded, unretarded,
and in-flight selection (pilot option) of either mode.
RETARDED MODE.—In the retarded mode of
delivery, the fins open to retard or slowdown the
weapon. Since the aircraft and the weapon are traveling
at the same speed when the weapon is released, the
weapon and the aircraft arrive at the target at the same
time. During low-level bombing, the aircraft could be
damaged; therefore, the retarded mode of delivery is
used during low-level bombing.
The fin assembly is positively armed in the retarded
configuration. In this configuration, the fin release
arming wire is looped over a permanent structure on the
bomb rack. As the weapon is released from the aircraft,
the arming wire is pulled from the fin release band, and
the spring-loaded fins pop open. The fins are forced to
the full-open position by the air stream, which causes
the weapon to rapidly decelerate and allows the
releasing aircraft sufficient time to safely clear the
target area.
UNRETARDED MODE.—In the unretarded
mode of delivery, the weapon is released from the
aircraft, and the fins remain in the closed position. The
weapon free falls to the target. In the unretarded mode
of delivery (without pilot option), the cotter/safety pin
installed in the fin release band is not removed or
replaced with an arming wire. However, the safety tag
that reads REMOVE BEFORE FLIGHT is removed.
IN-FLIGHT
SELECTION.—The
most
fre-
quently used mode for delivery is the in-flight selection
(pilot option) mode. The pilot can drop the weapon in
the retarded or unretarded mode. This is possible by
connecting the swivel loop of the fin release arming
wire to the tail arming solenoid of the bomb rack. If the
pilot energizes the arming solenoid upon weapon
release, the arming wire remains connected to the
arming solenoid and is pulled from the fin release band
at weapon release, which allows the fins to pop open
and results in a retarded delivery. If the pilot does not
energize the arming solenoid upon weapon release, the
arming wire is pulled free of the arming solenoid. This
allows it to remain in the fin release band, preventing
the fins from opening, which results in an unretarded
delivery.
BSU-85/B Air Inflatable Retarder
The BSU-85/B bomb fin attaches to the Mk
83 general-purpose bomb.
It
is
an air-inflatable
retarder designed for very low altitudes. It can be
dropped in either high-drag (retarded) or low-drag
(unretarded) mode (fig. 1-24). The BSU-85/B fin
1-26
