DECOYING DEVICES

LEARNING OBJECTIVE: Identify the purpose and use of decoy devices.

Decoy flares are dispensed from launching mechanisms on aircraft. They are fired during evasion tactics when threatened by enemy heat-seeking missiles.

The Mk 46 Mods 1, 1A, and 1C decoy flares are loaded into and launched from either the AN/ALE-39 dispensing set or the AN/ALE-37A chaff dispenser. The decoy flare (fig. 4-12) consists of a cylindrical aluminum case about 5.8 inches long and 1.42 inches in diameter. The base end of the flare is flanged to a maximum diameter of 1.495 inches to fit the counterbore in the chamber of the dispenser. The end

Figure 4-12.-Mk 46 Mod 1, MJU-8/B, A/B, MJU-22/B, SM 875/ALE and chaff package. 4-13

of the flare case opposite the flanged base is closed with an aluminum closure disk.

When properly installed in the chamber of a dispenser, the cartridge retainer fits snugly over and around the firing end of a corresponding Mk 131 impulse cartridge. When the cartridge is fired, gas pressure causes the hammer to move into the adapter, locking the adapter and the piston together. Gases from the fired cartridge expand to exert a pushing force against the piston. This removes the closure disk and ejects the flare grain. As the piston strikes the piston stop, the adapter to which the pull wire is firmly attached separates from the igniter cup. Then, the adapter travels with the flare grain. This action causes the igniter to move over the friction material on the crinkled end of the pull wire, igniting the ignition composition. Flame flashes through the longitudinal hole in the flare grain and ignites the first-fire composition in both the longitudinal hole and the cross hole. The first-fire composition ignites the flare grain on all surfaces.

The flare is rendered safe during normal handling operations by the segmented adapter. If the closure disk is accidentally displaced, the entire grain and the igniter assembly slips out of the flare case without igniting. The device arms only after an impulse cartridge is fired and bends the sharpened edges of the adapter so it is locked to the piston.

PRACTICE BOMB SIGNAL CARTRIDGES

LEARNING OBJECTIVE: Identify the purpose and use of practice bomb signal cartridges.

Practice bomb signal cartridges are used for day and night operations and as a visual indication of bomb impact and fuze function. Three types of signal cartridges are discussed in this section.

Mk 4 Mod 3 signal cartridge. The Mk 4 Mod 3 practice bomb signal cartridge (fig. 4-13) consists of an aluminum case. The rim end has a percussion primer, and the opposite end is sealed with an aluminum disk. The cartridge produces a flash of light and a white smoke puff. The Mk 4 Mod 3 is primarily used for night operations.

CXU-3/B and CXU-3A/B signal cartridges. The CXU-3/B and CXU-3A/B practice bomb signal cartridges (fig. 4-14) consists of a cylindrical aluminum case. The case is closed on one end with a percussion primer, and the opposite end is closed with a crimped-in-place aluminum cover (cap). The cartridge produces a dense, white smoke display for day missions.

CXU-4/B spotting charge. The CXU-4/B spotting charge (fig. 4-15) is a fire-free signal used with practice bomb BDU 45/B to provide a daytime visual indication of bomb impact point and fuse function.

Figure 4-13.-Practice bomb signal cartridge.

Figure 4-14.-Mk 4 Mod 3, CXU-3/B, and CXU-3A/B practice bomb signal cartridge.

HANDLING AND SAFETY PRECAUTIONS

LEARNING OBJECTIVE: Recognize the safety precautions to follow when working with pyrotechnics.

Pyrotechnic ammunition is one of the most widely used types of ammunition in naval aviation. Pyrotechnics of one type or another are carried in almost every Navy aircraft, including unarmed transport and training aircraft.

All pyrotechnic and screening devices, while designed and tested to be safe under normal conditions, are subject to accidental ignition. A general rule for the handling of pyrotechnic devices is as follows:

You should be constantly aware that pyrotechnics contain chemical components that are intended to burn with intense heat, and you should act accordingly.

Figure 4-15.-CXU-4/B spotting charge.

Pyrotechnic and screening devices are normally equipped with some type of safety pin, lock, or tape that is designed to prevent accidental activation of the initiation mechanism. Do NOT tamper with such equipment. Do NOT strike, bend, or otherwise remove the safety equipment until just before the device is launched Any devices that show signs of damage to the safety features are considered unserviceable; carefully put them to one side and promptly dispose of them according to current directives.

If a pyrotechnic device should accidentally ignite, it will result in a fire hazard. In a confined area, the gases generated by this combustion could present a serious toxic hazard. Signaling charges that contain propellant charges, designed to propel the pyrotechnic candle into the air, create an extremely dangerous missile hazard.

Pyrotechnic compositions characteristically contain their own oxidants; therefore, they do not depend on atmospheric oxygen for combustion. For this reason, exclusion of air, by whatever means, from a pyrotechnic fire is usually ineffective. Many pyrotechnic mixtures, particularly illuminating flare compositions, burn with intense heat (up to 4,500F). Normally, extinguishers are not useful in this kind of fire. Carbon dioxide extinguishers, in addition to being ineffective, are potential sources of danger because they tend to produce oxygen, which supports the combustion. Foam-type extinguishers are equally ineffective because they work on the exclusion-of-air principle.

Water, in flooding quantities and at low pressure, should be used to cool the surrounding area and to prevent the spread of the fire. Properly controlled and directed, water is the best fire-extinguishing agent for aircraft parachute flares burning in the open.

Pyrotechnic hazards are frequently increased by such factors as age, improper storage conditions, rough handling, moisture penetration, excessive temperatures, damage to shipping containers, and other mishaps that causes the devices to become unserviceable. In most cases, immediate danger does not exist. Unserviceable pyrotechnic and screening devices on ships at sea are put to one side for normal return to an appropriate shore station for disposition according to the instructions and regulations contained in NAVSEA OP 5, volume 1.

Conditions may develop that demand emergency disposal of potentially hazardous devices. In such cases, disposition is the responsibility of the commanding officer. Under NO circumstances, other than an extreme emergency, should ammunition, explosives, or other related hazardous materials be dumped at sea by a Navy vessel, aircraft, or activity without prior approval of the CNO. If, in the commanding officer's best judgement, immediate disposition is necessary to protect lives and property, the commanding officer should order such disposition by the most appropriate means available. In all cases, the commanding officer must notify Naval Sea Systems Command, at the earliest practical time, of the facts and circumstances.