[h=2]Information requested on the Practice Bomb Carrier (PBC)[/h]
The Light Stores Bomb Carriers should not be considered in isolation but with the pylons (carriers) they were mounted on. The Canberra B.(I)6s & B.(I)8s and subsequently the B.15s & B.16s were fitted with wing mounted pylons. The pylons could carry;
• a 1,000lb bomb, or
• a Rocket Launcher, or
• a Light Stores Bomb Carrier.
The two interdictor versions of the Canberra, when in the conventional armament role could be fitted with a Boulton Paul gunpack, that fitted snugly into the rear of the bomb-bay and special bomb doors with cut-outs for the gunpack were fitted. The gunpack contained four 20mm Hispano 'Aden' guns. These each could be loaded with 500 rounds, the muzzle velocity was relatively low and produced a firing rate of 600 rounds per minute. The remaining forward part of the bomb-bay could accommodate two 1,000lb bombs, but normally it was fitted with containers of parachute flares. The two wing pylons were used for the external carriage of 1,000lb bombs.
The Canberra B.15s & B.16s when in the conventional armament role used the wing pylons for the carriage of Microcell rocket launchers. These were metal-skinned, moulded reinforced glass-fibre boxes each holding 37 spin-stabilized 2 inch folding-fin rockets. The rocket launcher could be fitted with a rubberised nose cone to reduce drag and which disintegrated when the rockets were fired.
All four versions of the Canberra, as part of the UK's nuclear deterrent had the capability of delivering a tactical nuclear weapon. The forty-eight Canberra B.(I)6s & B.(I)8s were based in RAF Germany (RAFG) and under the auspices of Project E - an agreement between the USA and UK on the RAF's carriage of US nuclear weapons carried the American 1,650-lb Mk.7 tactical nuclear bomb. The weapons were, at all times, under US custody. These Canberra aircraft were assigned to NATO in Germany under the command of the Supreme Allied Commander Europe (SACEUR)- always a US officer, who with direct orders from the President of the US could authorise the release an use of nuclear weapons.
The thirty-two Canberra B.15 & B.16s in the RAF's Near East and Far East Air Forces were equipped with the British tactical nuclear weapon 'Red Beard' rather than the American Mk.7 tactical nuclear weapon. The operational use of these weapons was always under British control. The bomb was always referred to as 'Bomb HE, 2,000lb MC' weighing in at approximately 1,750lb, Red Beard was considerably lighter than the official service designation, which was based on the original technical requirement. The Red Beard a second-generation fission atomic bomb was Britain's first tactical nuclear weapon and had a 15 Kiloton yield similar to the 'Little Boy' atomic bomb dropped on Hiroshima. The body diameter at 28 inches was greater than was desirable relative to the overall length of 12ft. Furthermore, unlike a conventional bomb the nuclear compartment was mostly air and was tail-heavy. To compensate for this and to quickly stabilize the bomb after release, it was equipped with flip-out fins that were activated pneumatically, triggered by a lanyard attached to the aircraft.
It had become apparent that aircraft involved in high level bombing were extremely vulnerable to modern Surface to Air Missiles (SAMs) and remaining at low altitude for as long as possible would allow the bomber to minimise its detection. However, an aircraft releasing a nuclear weapon at low-level would most probably be vaporised by the fireball. During the Korean War 'toss-bombing' was used when pilots of fighter-bombers released their bombs with an upward flip of the plane so that the bomb was tossed into caves sheltering enemy troops. The United States Air Force and Navy developed a system which could accurately lob a nuclear weapon on to a target from low level. The system was named LABS (Low Altitude Bombing System) and was manufactured by Honeywell. It consisted of gyroscopes and an accelerometer and took airspeed inputs from the aircraft’s pitot system and altitude inputs from the static system.
The attacking airplane would approach the target at high speed and low altitude, in the case of the Canberra this was 434kts and 250ft above the ground, with full power being applied 3 seconds before pull up into a 3.4G loop with bomb release at a pre-determined angle so that it was lofted, or tossed, towards the target. In its manoeuvre the aircraft would reach about 6,000ft and the bomb around 10,000ft an be tossed around two miles. The LABS indicator had two needles, a horizontal one for pitch/G and a vertical one for roll and yaw. When the bomb was released it would arc upwards towards the target while the aircraft continued its loop when the nose came to 30 degrees below the horizon, the aircraft would be rolled upright while still descending to low level and accelerating away to escape at low-level from the 'atomic blast'.
Although with the initial LABS trials the bombs were loaded in the bomb-bay on Light Series Carriers , which were fastened directly to the main bomb beam. Whilst the aircraft had been strengthened to permit the opening of the bomb doors at 434kts and a perforated baffle to smooth out the turbulence, however it was found that to ensure a satisfactory and smooth release of the practice bombs the optimum position of a Light Series Carrier was on the bottom of an Avro Triple Carrier. With the introduction of the wing pylons , Light Stores Bomb Carriers mounted on the wing pylons were used for LABS training Each carrier held two 25lb practice bombs.
The Pylon was fitted on Rib 3 of the Canberra wings and was adaptable for bombing or rocket launching* roles.
A 1,000lb bomb wouldbe offered up to the open release unit and the single suspension lug would thenclose the jaws of the release unit and a spring loaded lever would form ageometric lock holding the jaws of the release unit closed. The spigot of the crutching unit would be turned and the bombwould be raised and crutched against the sole plate. When the store wasselected and triggered a solenoid would break the geometric lock and the bombwould fall free.
The Light StoresBomb Carrier
The Carrier waseffectively a light alloy container faired at both ends to which two smallpylons were welded. Each pylon containeda Type R release unit, a crutching mechanism, an electrical release mechanismand a manual release mechanism. Each pylon had a sole plate shaped to enable a25lb practice bomb to be stabilised against it. The top of the unit was shapedto match the contours of a 1,000lb bomb and in addition to a suspension lug ithad two locating studs which mated with the sole plate of the main pyloncarrier.
There was a mnemonic to remember the order in which they were dropped 'PiSo PoSi' - Port Inner, Starboard Outer, Port Outer & Starboard Inner. Contacts 1 & 3 on the auto selector switch were not connected and in conjunction with the selection on the LABS store selector panel only one bomb was released at a time. It was possible for a Navigator, having an early 'senior moment' to use the 12/24 way make the selection and this would then release the carrier and both bombs during the LABS manoeuvre - this actually happened to a B(I)8 Crew in RAFG. Very occasionally we flew with a single Light Stores Carrier on the port pylon and a 'sole-plate' would be fitted on the other(starboard) pylon. Again if the Navigator forgot this and selected the normal sequence, instead of a second bomb, the sole plate would be released and lost at sea!
*When the wing pylons were used to carry the Microcell rocket launchers this involved the removal of the bombing role cable loom an the bomb pylon screw jack and the associated fuzing and release units. These were the replaced with a rocket launching cable loom and its incorporated Ejector Release Unit. This enabled the rocket pod to be jettisoned in an emergency.
