stepper switch, causing the stepper switch to step from
the preset ARM position to the No. 1 position. This
fires the No. 1 impulse cartridge. The gas pressure,
generated by the fired cartridge, is ported through a gas
tube, internally along the side of the dispenser, into the
aft expansion chamber ahead of the aft flare.
As the gas pressure increases, the aft retaining lock
shear pin is cut, allowing the aft flare to eject. As the
timer end of the flare approaches the rear of the tube,
the arming finger of the arming mechanism engages the
yellow sealing ring. The sealing ring cams the arming
finger down, which, in turn, cams the arming hook up to
engage the green arming cap. This action allows the
flare to extend the lanyard. The lanyard extracts the
timer knob and arms or starts the flare functioning
When the pilot triggers the system again, the
stepper switch steps to the No. 2 position and fires the
cartridge. This meters the gas pressure directly into the
forward expansion chamber. As the gas pressure
increases, the forward retaining lock shear pin is cut.
This allows the forward flare to be dispensed in the
same manner as the aft flare. If the aft flare failed to
eject, the gas pressure generated for ejecting the
forward flare produces sufficient gas pressure to purge
both flares out of the tube.
The procedure for the remaining three tubes is the
same. The firing sequence of the breeches is stamped
into the metal of the breech caps, as shown in figure
Organizational-level maintenance is limited to a
visual inspection of the dispenser. You need to look for
damage, such as cracks or breaks in the aft retaining
obstructers in the breech sleeve, and frayed or broken
SUU-25F/A dispenser, you should refer to Dispenser
SUU-25F/A, NAVAIR 11-75AA-48.
REVIEW NUMBER 4
What impulse cartridge is installed in the
SUU-25F/A to launch flares?
What voltage fires the impulse cartridge?
When performing organizational-level main-
tenance on the SUU-25F/A, you should look
for what types of damage?
AN/ALE-29A COUNTERMEASURES CHAFF
The AN/ALE-29A countermeasure chaff dis-
pensing set, known as the chaff dispenser, is an
electronic countermeasure device. It may be installed in
almost all Navy combat aircraft. The chaff dispensing
set includes two dispenser assemblies, two dispenser
housings, two sequencer switches, and a programmer.
The cartridge in the chaff dispenser can eject various
load configurations of Mk 46 or MJU-8/B decoy flares
and RR-129 or RR-144 chaff.
Decoy flares are used during evasive maneuvers
against heat-seeking missiles. Chaff rounds consist of
fine-shredded metal strips contained in a cylindrical
metal container. When ejected from the chaff dispenser,
the metal strips are forced from the cylindrical
container and dispersed into the atmosphere. This jams
ground controlled radar installation or radar-controlled
Figure 10-18.Breech cap identification numbers.