The Tallboy was a bomb developed by Barnes Wallis in 1944. It weighed five tonnes and was developed primarily in order to penetrate large concrete structures against which earlier, smaller bombs proved ineffective.

Most large Allied World War II aircraft bombs had very thin skins to maximise the weight of explosive which a bomber could carry. Barnes Wallis developed the Tallboy as a bunker buster. It was very aerodynamic with a tail which caused it to spin. This allowed it to break the sound barrier as it fell. It had a much thicker skin than the typical World War II bomb so that it would survive the impact of hitting a hardened surface. When dropped on compacted earth it would penetrate over 40 meters into the ground.

W. J. Lawrence wrote about the Tallboy bomb in his book, No 5 Bomber Group (1951)

It was an extraordinary weapon, an apparent contradiction in terms, since it had at one and the same time the explosive force of a large high-capacity blast bomb and the penetrating power of an armour-piercing bomb. On the ground it was capable of displacing a million cubic feet (30,000 m³) of earth and made a crater which it would have taken 5,000 tons of earth to fill. It was ballistically perfect and in consequence had a very high terminal velocity, variously estimated at 3,600 and 3,700 feet per second (1.10 and 1.13 km/s), which was, of course, a good deal faster than sound so that, as with the V-2 rocket, the noise of its fall would be heard after that of the explosion.

It had to be dropped from a great height which limited its accuracy and the Lancaster bomber could only carry one at a time. It was used successfully at the Eperleques blockhouse, and also against the German battleship Tirpitz.

Vital statistics

See also

• Grand Slam bomb