Apparatus A.D. Type D Mk III (Service)

Over-all length

Maximum diameter

Time to eject

Lethal period

Visible deterrent

General: This rocket is designed to erect lethal wires vertically over a ship in the path of low-level or dive-bombing aircraft. The wire is carried into the air by a rocket and is suspended by a parachute, which is carried in a container in the head of the rocket motor. A parachute on the lower end of the wire opens when a planes strikes the wire and offers sufficient resistance to thrown the aircraft momentarily out of control or to cause it to break up. The apparatus remains lethal until its lower parachute strikes the water, about 7 sec. after ejection of the upper parachute. It continues to act as a visib-le deterrent for an additional 5 sec., by which time the upper parachute has fallen to an ineffective height.

Description: The rocket consists of a tube filled with rocket-propelling composition having a conical hole down the center. This hole is aligned with that in a choke in the after end of the tube. A length of quickmatch and a gunpowder burster charge are loca-ted in the forward end of the tube immediately below the parachute container. The para-chute container holds the folded parachute and is closed at the forward end by a metal cup. The parachute is connected to the forward end of the rocket motor tube.

A steel bridle and a cable are attached to the motor tube. The cable is fitted with a loop for attachment to the main cable from the lower canister.

The lower canister consists of a cylindrical or rectangular box, which contains about 400 ft. of cable is attached a 38-in. drag parachute. The forward end of the cable is at-tached to the cable leading from the bridle on the rocket motor.

Operation: When the projector, loaded with rocket and cartridge, is fired, the flash from the cartridge ignites the rocket propellant composition, which propels the rocket along its trajectory. As the rocket rises, it uncoils and carries with it the main cable from the lower container, which remains fixed to the rocket projector. When the cable is com-pletely uncoiled, it withdraws the drag parachute from the container. This parachute is fitted with an explosive link arrangement, allowing the parachute to open 3 sec. after firing.

When the propellant composition is completely burned out, the length of quickmatch in the head of the tube is ignited and in turn initiates the gunpowder burster charge. This charge ejects the upper parachute from its container, leaving the rocket tube and the wire cable suspended in the air.

When an aircraft strikes the wire, the lower parachute opens and offers sufficient re-sistance to throw the plane out of control or to cause it to break up.