AN/ALE-29A COUNTERMEASURES CHAFF DISPENSING SET

The AN/ALE-29A countermeasure chaff dispensing set, known as the chaff dispenser, is an electronic countermeasures device. It maybe 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 missiles.

Dispenser Assemblies

The dispenser assembly (fig. 10-36) contains two major subassemblies-a glass-reinforced phenolic plastic block and a sandwich-type primed circuit board. The block has 30 holes so you can load the payload units. There are four quick-release, positive-lock studs so you can secure the block in the dispenser housing, and two telescoping handles to make it easier to handle.

The sandwich-type printed circuit board contains the circuitry and jacks so you can install 30 electrically initiated Mk 131 impulse cartridges. You must also install a connector to act as an interface between the dispenser assembly and the dispenser housing.

You load the dispenser by putting the 30 payload units (in plastic sleeves with plastic cartridge retainers installed) into the block. Install an impulse cartridge in each of the 30 jacks on the printed circuit board. Then, attach the board to the block by two captive screws.

NOTE: Installation of the impulse cartridges must be accomplished in a designated RF (radio frequency) free area.

Finally, install the loaded dispenser assembly in the dispenser housing. You need to secure it with the four positive-lock studs of the dispenser block. The payload units are forced from the plastic sleeves by the gas pressure generated when the impulse cartridges are fired. The chaff sleeve extractor, shown in figure 10-36, is used during dispenser download procedures.

Dispenser Housings

There are two different housing configurations available, as shown in figure 10-37. You can identify the housings by the mounting flange configuration, number and arrangement of mounting fasteners, location of the sequence switch, and the cable arrangement. These configurations are supplied so aircraft manufacturers have flexibility in mounting locations.

You don't remove the housing assemblies from the aircraft when loading. You do remove the dispenser assembly from the housing assembly by unlocking the four positive-lock studs. Move the dispenser assembly to a designated area and load it. Then, return it to the aircraft and reinstall it in the dispenser housing. Safety switches, installed in the aircraft near the dispenser housings, make the dispenser's assemblies electrically safe when the safety pin or flag assemblies are installed.

Figure 10-36.-AN/ALE-29A countermeasures chaff dispensing set.

Figure 10-37.-Dispenser housings.

When the dispensers are loaded, the safety pin or flag assemblies must remain installed until just before fight.

The rear of the housing assembly has a dispenser interconnect that electrically connects the dispenser assembly to the system. When you are installing the dispenser assembly into the housing assembly, you should use a guide pin to ensure proper alignment of the electrical connectors.

Sequencer Switch

Two sequencer switches (fig. 10-38) are used in a system-one for the right- and left-dispenser assemblies. The sequencer switch is a solenoidactuated, multideck, rotary stepping switch contained in a hermetically sealed case.

The sequencer switch is actuated by control signals received nom the programmer. Each control signal from the programmer actuates a relay in the sequencer switch, which applies 28-volt dc to the rotary switch. As the rotary steps, a firing pulse is supplied directly from the aircraft's 28-volt dc power supply. This firing pulse is directed to the applicable impulse cartridge in the dispenser assembly.

Dispensing starts with the selection of one or both dispensers (right or left) from the cockpit and the initiation of the dispensing switch. When only one dispenser has been selected and is emptied, the programmer control pulses are. automatically transferred to the second sequencer switch. When both dispensers are selected by the cockpit control, simultaneous signals are directed to both sequencer switches. The sequencer switches are connected to the dispenser housing by an electrical cable supplied as part of the dispenser housing.

Dispensing Set Programmer

The dispensing set programmer (fig. 10-39) provides electronic control of the dispensing modes. The AN/ALE-39A programmer generates control signals for the programmed payload ejection sequences. It also generates control signals for single ejection of payloads initiated manually. Manual (single) dispensing is performed during a programmed dispensing sequence without disrupting the program.