The British Grand Slam

[Jim]

The Grand Slam was a 22,000 lb bomb used by RAF Bomber Command against strategic targets during the Second World War, invented by Barnes Wallis more famous for his bouncing bomb used for dam busting made into the film "Dam Busters"

The largest of the British war-time bombs was the well-known ‘Grand Slam’, a 9979-kg (22,000-lb) missile designed chiefly for deep penetration, equipped with aerodynamically shaped fins to impart an assisting twist to its fall. Forty-one of these monsters were dropped by specially-modified Avro Lancaster’s in 1945, the first on 14 March when Lancaster B.Mk 1 (Special) PD112 of No, 617 Squadron, with Squadron-Leader C.C. Calder at the controls, demolished two spans of the Bielefeld Viaduct with one of these weapons only a single day after the first test-drop had been made. British heavy bombs of 5443-kg (12,000-lb) capacity were of two types, the most sophisticated being the Tallboy’ designed for deep penetration, and of which no less than 854 were dropped by Avro Lancaster’s following the first attack with them on the night of 8/9 June 1944.

The 1814-kg (4,000-lb) HCMk III HE bomb had three pistols and detonators in the nose. In the centre of the bomb there was a continuous tube with exploders linked into the central detonator. These bombs had a very high explosive filling to overall weight ratio.

While the ‘Tallboy’ was of conventional streamlined shape, the other 5443-kg missile was a departure from common practice in that it was cylindrical and was in fact formed from three 1814-kg (4,000-lb) ‘Cookies’ bolted together (the sections being clearly visible) with an annular-ringed six-fin tail attached. This was the General-Purpose ‘Factory Buster’, also much used in 1944, but in fact first used during a raid on the Dortmund-Ems Canal during the hours of darkness of 15/16 September in the previous year. ‘Big, beautiful’ bombs were pioneered by the 907-kg (2,000-lb) version first used during the night attack on the Emden shipyards on 31st March/1st April 1941. However, a comparison of weight alone is deceptive, since the explosive power of the later bomb was greater than that of the fillings used at the beginning of the war, when a 907-kg ‘heavy’ certainly existed in armour-piercing form for attacks on shipping, although the version of a mere 227-kg (500-lb) weapon was the accepted ‘big bomb’ in the RAF.

A typical scene on any Lancaster base during later years of World War II: a 3629-kg (8,000-lb) HC blast bomb is brought up by tractor for loading into the capacious bomb bay of a Lancaster. The Lancaster, Manchester and Halifax could carry these bombs internally.

The ordinary ‘Cookie’ had made its operational debut over Wilhelmshaven on 8 July 1942, observers at the time reporting that ‘whole houses took to ’the air’, thus gaining for the weapon the name of ‘Block Buster’ in the UK, although the Germans knew the type as Bezirkbomben. The existence of these was, however, not announced until some time after their first use, not in fact until September, and it was not for a further two years that the general public was to know the name of the man who had taken such a prominent part in the development of British wartime bombs, Air Commodore Patrick Huskinson, who had himself been blinded during a raid by the Luftwaffe in 1941.

An 1814-kg (4,000-lb) HCMk I high-explosive bomb is wheeled up to a Mosquito B.Mk IV. This was an early version with a single pistol and detonator in the nose. This example is painted in the yellow-buff shade originally used on high-explosive bombs.

Specification:
GP 'Factory Buster'
Type: General-Purpose High Explosive Bomb
Weight: 5443 kg (12,000 lb)
Dimensions:
Length 5.33 m (17 ft 6 in);
Diameter 1.02 m (3 ft 4 in)
Filling: 2358.7 kg (5,200 lb) of Torpex 'cemented' within a 25.4-mm ( 1-in) jacket of TNT

Here is some footage of the Grand Slam being dropped over Germany..

YouTube Video

[Dave]

"In the last war, a twenty pound bomb was considered pretty grim..."

As the video points out among the excellent footage, the aircraft were the limiting factor. In this photo the first of the "Blockbuster" 4000 pounders to arrive in Malta in 1941 is loaded onto a Wellington bomber. At the time this was the only aircraft in Malta that was capable of picking the bomb up.
First used on the night of 16 - 17th October 1941 where a heavy raid was carried out on Naples. Pilots were instructed not to bring the bomb back as the undercarriage could not support the weight.