Breech, Breech Cap, and Breech Lead

There are two breeches, two breech caps, and two breech leads for each tube of the dispenser. The breech is screwed into the bulkhead so a CUU-44 impulse cartridge can be installed The breech cap, containing the firing pin, screws onto the breech. The breech lead connects to the breech cap and provides a path for the 28-volt dc required to fire the impulse cartridge.

Downloading Breech and Downloading Breech Cap

There is one downloading breech and a downloading breech cap for each tube of the dispenser. The downloading breech mounts to the bulkhead. The downloading breech cap screws onto the downloading breech. With the downloading breech cap removed, the downloading breech lets you insert the loading, unloading, cleaning, pushrod tool so the stores can be easily removed during downloading procedures. It also prevents air pressure buildup in the tubes when _{uploading stores.} Reinstall the downloading breech caps after the loading or unloading procedures have been completed.

Manifold

The manifold has eight manifold breech lead receptacles for connection of the breech leads. It also has two test socket assemblies you can use during dispenser electrical test procedures.

Stepper Switch

The stepper switch provides sequential firing of the impulse cartridges. The switch has 10 functional settings-one safe setting, one arm setting, and eight firing steps. Always place the stepper switch in the safe position during dispenser loading and unloading. Move the switch to the arm position during aircraft arming procedures just before flight.

Forward and Aft Retaining Lock

Each of the four dispenser tubes contains a forward retaining lock, an aft retaining lock, and an arming mechanism.

The forward and aft retaining locks, when in the locked position, protrude into the dispenser tube. This prevents loaded stores from being inadvertently ejected by g forces during aircraft catapult launches.

The forward retaining lock is located between the dispenser outer skin and the tube near the midpoint of the dispenser. You can move the retainer lock from the either the locked or unlocked position through an access door located on either side of the dispenser. Before loading a store, rotate the retaining lock to the unlocked position. This pivots the retainer lock out of the tube. After the store has been loaded, rotate the retaining lock to the locked position, and secure it by installing a shear pin. The forward retaining lock retains the forward loaded store only.

The aft retaining lock is attached to the aft bulkhead and retains the aft loaded store. It is also secured in the locked position by installing a shear pin.

Arming Mechanism

The arming mechanism is located in the aft end of the dispenser tube. The arming mechanism initiates the arming sequence of a store as it is ejected from the tube.

The dispenser is suspended by two screw-type lugs spaced 14 inches apart. The area around the suspension lugs has a hardback reinforcement to permit sway bracing and forced ejection of the dispenser.

Two electrical receptacles, VI and V2, are located forward and aft of the suspension lugs, respectively. Both receptacles give you away to electrically connect the dispenser to the aircraft weapons control system. Only one receptacle is used at a time. The electrical configuration of the rack determines the receptacle you will use.

An electrical wiring harness is routed internally from electrical connectors V1 and V2 to the stepper switch. The wiring harness is interrupted by a safety switch that is normally in the closed position. When the safety pin and flag assembly are inserted, the safety switch is held in the open position and the electrical circuits are grounded, making the dispenser electrically safe.

Functional Description

When you load a dispenser tube with munitions, each pair of flares/sonobuoys are configured with an ADU-381/A flare adapter kit. Also, you should enclose sonobuoys in a Mylar sheet (protective sleeve) and install a protective disk.

A yellow-colored sealing ring is pressed on each end of the munition as a seal between the munition and the tube body. This prevents gas pressure from escaping during ejection. A green-colored arming cap is installed on the timer end of a flare or on the rotochute end of a sonobuoy. The green arming cap lanyard is connected to the timer knob of the flare, and then pressed on over the flange of the sealing ring. When you install an arming cap on the sonobuoy, the lanyard is not used. Mount a white cross-shaped plastic spacer on the aft sealing ring of the forward munition. This provides enough space between the forward and aft munition to provide an expansion chamber for ejecting the aft munition.

After you have installed the adapter, install the munitions in the dispenser tube.

When a SUU-25F/A dispenser is fully loaded and uploaded on the aircraft, the pilot may eject flares. The pilot must first select the weapons control system, and then trigger the dispensing switch. A 28-volt dc electrical signal passes through an electrical cable from the aircraft to either receptacle J1 or J2 of the dispenser. The signal is routed from the dispenser receptacle to the 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 sequence.

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 10-35.

Maintenance Requirements

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 locks or suspension lugs, unburned pellets or obstructors in the breech sleeve, and frayed or broken breech leads.

For further information concerning the SUU-25F/A dispenser, you should refer to Dispenser SUU-25F/A, NAVAIR 11-75AA-48.

Figure 10-35.-Breech cap identification numbers.