Click for Site Directory

3. The Bomb and Parachute Arming Scheme

                    Bombs and Parachutes

The bombs used contained a High Explosive (H.E.) with a mechanism to make them live and armed and detonate.

The bombs used throughout the war were of two types:

Bomb H.E. (High Explosive), A.A.D. (Armament, Air Defence), No.4 Mk IV

 

Bomb H.E. (High Explosive), A.A.D. (Armament, Air Defence), No.6-A Mk II

1.  Bomb H.E., A.A.D., No.4 Mk IV

This has a magazine inserted into a magazine holder and the magazine contains the High Explosive charge.

The magazine holder is in the shape of a can made from thin metal. The lower end is closed an carries a lug for attaching the stabiliser strop of the parachute. Near the closed end is a ridge around which the split skirt of the stabilising parachute fits. The other end is flanged to permit the magazine to the percussion unit. The flange carries a sealing washer.

The explosive charge consists of a bursting charge and a detonator.  The bursting charge is either a compound T.N.T., or Tetrytol (T.N.T. and Tetryl) and may be paper wrapped pellets or poured and moulded into the magazine holder. On top of the charge is a felt washer.

The detonator fits into a cavity in the bursting charge and brings about the detonation of the bursting charge.

There is a percussion unit that contains the mechanism to arm and fire the bomb. It is secured to the magazine holder by a knurled ring.

Percussion unit shutter

This houses the primer in a crossbore is mounted in a guide channel across the inside of the percussion unit body. It is held to one side against the action of the shutter spring by the arming pin, so that the primer is offset from the stroke of the firing pin when the bomb is unarmed.

The arming pin is a short rod with a knurled thread and secures a shear collar to the end of the rod extending from the shutter through the side of the percussion unit body. The arming pin is held in the spring  shear collar by means of a washer and a shear wire.

There is a safety pin that extends sideways into the shutter and locks it. B The pin is pressed into the locking position against the safety pin by means of a safety plug which is screwed into the percussion unit body. A warning tab is attached to the safety plug.

The firing pin is located in the central bore in the percussion unit body. In the unarmed position the firing pin is in line with a hole in the shutter so that the firing pin can be depressed without damaging the point of the firing pin. The firing pin head slides in the firing pin housing and has a flat underside surface. A firing pin spring presses against the underside of the underside of the firing

The firing pin ring is supported between the swivel housing and the swivel housing cup. When the bomb is armed any blow on the firing pin ring depresses the firing pin and fires the primer, which in turn causes the detonator to detonate the bursting charge.

The swivel is to attach the shock absorber strop to the percussion unit.

The swivel housing  screws into the swivel housing cup, the firing pin ring being supported between the two. The swivel housing cup is held between the head of the firing pin and the lip around the open end of the firing pin housing  by the pressure of the firing pin spring.

 

 

   

          2.Bomb H.E., A.A.D., No.6-A Mk II

This bomb is the same weight as Bomb H.E., A.A.D, No.4 Mk IV and contains the same amount of charge. The method of construction and

 arming are different The construction consists almost entirely of pressings. And the final joint is a rolled one. Therefore having once

 been assembled, the bomb cannot be taken apart. The bomb consists of two principal parts. The magazine and the percussion unit. The

 magazine consists of a. detonator holder and a bursting charge. The magazine holder is made of thin sheet metal drawn in the shape of

 a can. The upper half of the holder is attached to the percussion unit and the lower half is sealed to the upper half by a rolled joint.

 The detonator holder, which contains a compartment for the detonator, is also made of sheet metal and slides into the upper half of

 the magazine holder. The bursting charge may be the same as that using the Bomb H.E., A.A.D., No.4 Mk IV, or a compound of  Pentolite

 and T.N.T. Once the magazine has been filled, it is sealed at the roll joint and the bursting charge cannot be removed. The percussion

 unit contains the mechanism to arm and fire the bomb. It is sold to the upper half of the magazine holder. Other component parts are

 the Shutter, which houses the primer and is pivoted at one end. A shutter spring at this pivot holds the shutter, so the primer is offset

 from the stroke of the firing pin when the bomb is unarmed. The shutter is counterbalanced to prevent the bomb from being affected

 by side rose. The free end of the shutter has a cord attached to it. The other end of the cord is attached to a small drum on the spindle

 of the arming vane. The arming vane is a wind vane on the bomb. When the bomb is drawn through the airs at a peed of 140 mile per

 hour, the vane turns and winds the cord onto the drum on the spindle of the arming vane, drawing the primary in the shutter directly

 beneath the firing pin. The firing mechanism. Is similar to the corresponding parts of the Bomb H.E., A.A.D., No.4 Mk IV, except that the

 swivel housing is made in one piece, which performs the functions of the combined swivel housing and swivel housing cup of the Bomb

 H.E., A.A.D., No.4 Mk IV and the firing pin ring is secured to the swivel housing with six more screws.

 

 

   Click Here to see 4. The Disassembly of the Bombs on Very Low Altitude Barrage Balloons.*

Click Here to See 2.The Use of Inertia Links on Very Low Altitude Barrage Balloons.*

Click for Site Directory