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.
The MAU-91 fin is attached to the Mk 83 bomb by
fin adapter ADU-320/B. 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 airstream, 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. 1-30). The BSU-85/B fin
1-32
