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Tallboy
Royal Air Force Bomber Command, 1942-1945. CH15363.jpg
RAF ground crew handling the Tallboy that was later dropped on the La Coupole V-weapon site at Wizernes, France, 1944
TypeEarthquake bomb
Place of originUnited Kingdom
Service history
In service8 June 1944 – 25 April 1945
Used byNo. 9 Squadron RAF, No. 617 Squadron RAF
WarsWorld War II
Production history
DesignerBarnes Wallis
ManufacturerVickers
No. built854[1]
Specifications
MassApprox 12,000 lb (5,400 kg)
Length21 ft (6.4 m)
Diameter38 in (97 cm)

FillingTorpex D1
Filling weight5,200 lb (2,400 kg)
Detonation
mechanism
No. 58 fuze, built from No. 30 Pistol (impact detonation) or No. 47 time delay fuze inserted into tetryl boosters in the rear of the casing.

Tallboy or Bomb, Medium Capacity, 12,000 lb was an earthquake bomb developed by the British aeronautical engineer Barnes Wallis and used by the Royal Air Force (RAF) during the Second World War.[a]

At 5 long tons (5.1 t), it could be carried only by a modified model of the Avro Lancaster heavy bomber. It proved to be effective against large, fortified structures against which conventional bombing had proved ineffective.

History

Wallis presented his ideas for a 10-ton bomb in his 1941 paper "A Note on a Method of Attacking the Axis Powers", which showed that a very large bomb exploding deep underground next to a target would transmit the shock into the foundations of the target, particularly since shock waves are transmitted through the ground more strongly than through air.

Wallis designed the "Victory Bomber" of 50 long tons (51 t), which would fly at 320 mph (510 km/h) at 45,000 ft (14,000 m) to carry the heavy bomb over 4,000 mi (6,400 km), but the Air Ministry opposed a single-bomb aircraft, and the idea was not pursued after 1942.

The design and production of Tallboy was undertaken without a contract on the initiative of the Ministry, following Wallis' 1942 paper "Spherical Bomb—Surface Torpedo" and the design of the "bouncing bomb" for the Dam Busters of Operation Chastise. The RAF therefore used bombs which they had not purchased and which therefore remained the property of Vickers the manufacturer. This situation was normalised once the weapon’s capabilities were established.

Accomplishments of the Tallboy included 24 June 1944 Operation Crossbow attack on La Coupole which undermined the foundations of the V-2 assembly bunker and a Tallboy attack on the Saumur tunnel on 8–9 June 1944, when bombs passed straight through the hill and exploded inside the tunnel 60 ft (18 m) below the surface.[2]

The last of the Kriegsmarine's Bismarck-class battleships, the Tirpitz, was sunk by an air attack using Tallboys in Operation Catechism.

Design

Most large Allied, particularly British, Second World War aircraft bombs (blockbuster bombs) had very thin skins to maximize the weight of explosive that a bomber could carry. This was an improvement on the early part of the war when the explosive content of British bombs was low.

To be able to penetrate the earth (or fortified targets) without breaking apart, the casing of the Tallboy had to be strong. Each was cast in one piece of high-tensile steel that would enable it to survive the impact before detonation. At the same time, to achieve the penetration required, Wallis designed the Tallboy to be aerodynamically clean so that, when dropped from a great height, it would reach a much higher terminal velocity than traditional bomb designs.

In the final design, the No. 78 Mark I tail of the bomb was about half the overall length of the finished weapon; the bomb casing was some 10 ft (3.0 m) of the overall 21 ft (6.4 m) length. Initially, the bomb had a tendency to tumble and the tail was modified; the fins were given a slight twist so that the bomb spun as it fell. The gyroscopic effect thus generated stopped the pitching and yawing, improving aerodynamics and accuracy.

The Tallboy was designed to be dropped from an optimal altitude of 18,000 ft (5,500 m) at a forward speed of 170 mph (270 km/h), hitting at 750 mph (1,210 km/h).[3] It made a crater 80 ft (24 m) deep and 100 ft (30 m) across and could go through 16 ft (4.9 m) of concrete.[1]

The weight of the Tallboy (approximately 12,000 lb or 5,400 kg) and the high altitude required of the bombing aircraft meant that the Avro Lancasters used had to be specially adapted. Armour plating and even defensive armament were removed to reduce weight, and the bomb-bay doors had to be adapted.

No. 617 Squadron were trained on the Stabilizing Automatic Bomb Sight (SABS). Corrections had to be made for temperature, wind speed and other factors. The sight was effective only if the target could be clearly identified. Several missions were cancelled or unsuccessful because of this limitation.

For use on underground targets, the bomb was fitted with three separate inertia No. 58 Mark I Tail Pistols (firing mechanisms). These triggered detonation after a pre-set delay, which gave the bomb sufficient time to penetrate the target before exploding. Depending on mission requirements, the time delay could be set to 30 seconds or 30 minutes after impact.

To guarantee detonation, three Type 47 long delay fuzes were fitted inside the rear of the bomb. This dramatically improved reliability of the weapon; even if two of the fuzes failed, the third would trigger detonation. At least 2 Tallboys failed to explode, one during the second attack on the Sorpe dam; it was found during repairs in late 1958 when the reservoir was emptied, and a second was found in Świnoujście in Poland (formerly Swinemünde) in 2020.[4] This second bomb detonated in October 2020 while being remotely defused.[5]

The bomb was aimed at the target during an operation and proved capable of penetrating deep into hardened reinforced concrete when it hit. This, however, was not the primary intention of Barnes Wallis's design. The bomb was designed to make impact close to the target, penetrate the soil or rock beneath or around the target, and then detonate, transferring all of its energy into the structure, or creating a camouflet (cavern or crater) into which the target would fall.

This 'earthquake' effect caused more damage than even a direct hit that penetrated the armour of a target, since even a burst inside a bunker would only damage the surroundings, with the blast dissipating rapidly through the air. An earthquake impact shook the whole target and caused structural damage to all parts of it, making repair uneconomic. The attack reports below should be considered with this in mind.

An alternative technique was to arrange detonation depth so that the crater broke the surface—useful for attacking railway marshalling yards and similar targets. The Tallboy produced an 80 ft (24 m) crater with depths up to 100 ft (30 m), unlike conventional bombs which would produce many shallow craters across a target—each one of which could later be filled in rapidly with earth-moving equipment. Such a huge hole was time-consuming to fill; multiple trucks and bulldozers could not be fitted around the periphery of the hole to speed the process.

Manufacturing

Tallboys were largely hand-made, requiring much labour during each manufacturing stage. The materials used were costly, with precise engineering requirements in casting and machining. To increase penetrative power, a large, specially hardened, steel plug had to be precisely machined and mated to a recess in the nose of the bomb. The ogive had to be perfectly symmetrical to ensure optimum aerodynamic performance. This was no easy task when manipulating a bomb casing with the size and weight of a Tallboy.[citation needed]

The Torpex filling was poured by hand into the base of the upturned casing after melting it in "kettles". The final stage of explosive filling required that a one-inch layer of pure TNT be poured over the Torpex filling, followed by sealing the base with a 4 in (100 mm) layer of woodmeal-wax composite with three cylindrical recesses fitted with the explosive boosters and into which three chemical time-fuses were inserted when the bomb was armed.[citation needed]

Tallboys were not considered expendable, and if not used on a raid were to be brought back to base rather than safely jettisoned into the sea. The value of the weapon offset the additional risk to the aircrew.[6] Given their high unit cost, Tallboys were used exclusively against high-value strategic targets that could not be destroyed by other means. When it was found that the Lancaster could be modified to carry a bomb larger than the Tallboy, Wallis produced the even larger Grand Slam bomb.[citation needed]

Tallboy operations

June – August 1944

Six Tallboy bombs in a bomb dump at Bardney, Lincolnshire prior to being loaded on No. 9 Squadron RAF aircraft in October or November 1944
Six Tallboy bombs in a bomb dump at Bardney, Lincolnshire prior to being loaded on No. 9 Squadron RAF aircraft in October or November 1944

Operation Crossbow

Crossbow was the code name for measures to counter the German V-1 flying bomb ("buzz bomb" or "doodlebug") and V-2 rocket weapons. Tallboys were used by the British to destroy several missile sites.

19 June 1944Watten

24 June 1944Wizernes

25 June 1944Siracourt V-1 bunker

4 July 1944Saint-Leu-d'Esserent

External image
image icon Bomb damage at Mimoyecques V-Weapon Site

6 July 1944Mimoyecques

Damage to the Fortress of Mimoyecques from Allied air attacks, including attacks with Tallboy bombs.
Damage to the Fortress of Mimoyecques from Allied air attacks, including attacks with Tallboy bombs.

17 July 1944Wizernes

27 July 1944 – Watten

31 July 1944Rilly La Montagne

Sorties against German dockyards

Shipping in the English Channel and the Atlantic Ocean were threatened by U-boats and E-boats stationed in France. U-boat docks were protected against conventional aerial bombardment by thick concrete roofs.

14 June 1944Le Havre

15 June 1944Boulogne harbour

5 August 1944Brest

6 August 1944Keroman

7 August 1944Lorient

8 August 1944La Pallice

28 August 1944IJmuiden

September – November 1944

23/24 September 1944Dortmund-Ems Canal near Ladbergen, north of Münster

7 October 1944 – Kembs Dam north of Basle

15 October 1944Sorpe dam

Raids on Tirpitz

The German battleship Tirpitz was a threat against convoys sailing to and from the Soviet Union.

15 September 1944 – (Operation Paravane)

29 October 1944 – (Operation Obviate)

12 November 1944 – (Operation Catechism)

December 1944 – April 1945

The 11-foot thick (3.4 m) concrete roof of submarine bunker "Fink II" in Hamburg, after having been penetrated by a Tallboy in early April 1945
The 11-foot thick (3.4 m) concrete roof of submarine bunker "Fink II" in Hamburg, after having been penetrated by a Tallboy in early April 1945

Bombing of U-boat pens, December 1944 – April 1945

15 December 1944 – IJmuiden on the Dutch coast,

12 January 1945Bergen

3 February 1945 – IJmuiden & Poortershaven

9 April 1945Hamburg

18 April 1945Heligoland

19 April 1945 – Heligoland

8 December, 11 December 1944

21 December 1944Politz

14 March 1945Bielefeld and Arnsberg viaducts

15 March 1945 – Arnsberg viaduct

16 April 1945pocket battleship Lützow

25 April 1945Berghof

Post war

The last of the V bombers – the Handley Page Victor – was designed to be able to carry a bomb load that could include a load of two Tallboys internally, or one Grand Slam plus assorted smaller weapons.

Unexploded ordnance

In September 2019, a Tallboy bomb was found in the Piast Canal in northwest Poland near the town of Świnoujście and scheduled for defusing.[38] The bomb had been dropped in the April 1945 attack on the Lützow, a German cruiser.[38] In October 2020, the Tallboy wound up detonating during a deflagration operation, but there were no reported injuries to divers nor any damage to the port infrastructure from the underwater explosion.[39]

United States use

The T-10 was an American-made version of the 12,000 lb (5,443 kg) Tallboy modified to use standard American components. Development was started in late 1944 and plans were made to drop them on the island strongholds of the Pacific to aid in softening their defences before amphibious assaults. No bombs were used operationally since the capitulation of Japan following the atomic bombings of Hiroshima and Nagasaki negated their need. In the late 1950s the T-10 was re-designated the M-121. During the Korean War a number of T-10s were converted to the radio-guided Tarzon bomb and were dropped by Boeing B-29 Superfortresses to destroy railroad bridges and reservoir dams.[40]

After the Korean War ended and the B-29 and B-36 bombers were retired, the United States Air Force no longer had an aircraft that could drop the M-121, and the bombs were put in storage. Production of the T-10 ended in 1955. The B-36 was the last operational aircraft that could drop a fully assembled Tallboy type bomb in the conventional way.[b] During the Vietnam War, some M-121s, minus their rear streamlined shrouds and tail fin assemblies, were shipped to Vietnam for Commando Vault missions where the warheads were incorporated into the BLU-82 weapons dropped by C-130s using radar control in order to clear a helicopter landing zone. The warheads were mounted on a platform and pulled by parachutes from the rear-loading ramp of C-130s. After clearing the aircraft the large extraction chutes and pallets were cut away and small triangular chutes stabilized the large warhead until impact. A three-foot (91 cm) nose probe detonated the bomb at the correct stand-off distance. One of the last of the World War II Tallboy designs was dropped during a Commando Vault mission to clear a landing zone for helicopters on a ridge during the 1969 Battle of Hamburger Hill in Vietnam. Dropping from 3,000 m (10,000 ft), the bomb hit exactly where it was needed. The Commando Vault missions were more accurate in bomb delivery on target than the more modern B-52s.[41][c]

Work still progressed on the 43,000 lb (20,000 kg) T-12 Cloudmaker, which could be carried by the Convair B-36A.[42]

See also

Notes

  1. ^ "Medium capacity" refers to the ratio of bomb case to explosive filling; in the case of the Tallboy, this was less than 50 per cent explosive by weight, in contrast to "high capacity" bombs like the Blockbuster bombs, in which up to three-quarters of their weight was the explosive.
  2. ^ The B-52 bomb bay lacked the length required to load a Tallboy.
  3. ^ The use of any type or make of the Tallboy ended with the Vietnam War. No bombs were dropped during the Gulf War in 1991 as none were in storage for the USAF. The large bombs dropped by C-130s during the Gulf War in 1991 were of the 6,800 kg (15,000 lb) type BLU-82.
  1. ^ a b Bombs Weapons Rockets Aircraft Ordnance Archived 30 August 2005 at the Wayback Machine
  2. ^ a b RAF staff 2004
  3. ^ Ellis 1998, p. 297.
  4. ^ "Neutralization of the Tallboy bomb" (in Polish). Retrieved 12 October 2020.
  5. ^ Morrison, Sean (14 October 2020). "Biggest World War Two bomb found in Poland explodes while being defused". Evening Standard. London. Retrieved 14 October 2020.
  6. ^ Harris 2005, p. 237.
  7. ^ a b c d e RAF staff 2005, June 1944
  8. ^ a b c RAF staff 2005, July 1944
  9. ^ Collier 1976, pp. 68, 84.
  10. ^ Brickhill 1951, p. [page needed].
  11. ^ Zaloga 2008, pp. 14–16.
  12. ^ "The Raids on Wizernes Rocket Base". The Dambusters. Archived from the original on 9 August 2013.
  13. ^ "World War II German hardened A4/V2 rocket launch sites". Retrieved 17 February 2008.
  14. ^ "Flight Lieutenant William Reid VC". Telegraph. 29 November 2001. Retrieved 17 February 2008.
  15. ^ Jones 2002, pp. 254.
  16. ^ RAF staff 2005, August 1944
  17. ^ a b c d e f g Keable 2008.
  18. ^ a b RAF staff 2005, September 1944
  19. ^ a b c RAF staff 2005, October 1944
  20. ^ Bishop 2012, p. 339.
  21. ^ Sweetman 2000, p. 121.
  22. ^ Brickhill 1951, p. 225.
  23. ^ RAF staff 2005b.
  24. ^ a b Ziemke 1960, p. 311.
  25. ^ Garzke & Dulin 1985, pp. 272–273.
  26. ^ RAF staff 2005, October 1944
  27. ^ RAF staff 2005, December 1944
  28. ^ RAF staff 2005, January 1945
  29. ^ RAF staff 2005, February 1945
  30. ^ a b c d RAF staff 2005, April and May 1945
  31. ^ Jones 2002, pp. 507, 524.
  32. ^ Murray 2005.
  33. ^ Jones 2002, pp. 507–508, 532.
  34. ^ a b RAF staff 2005, March 1945
  35. ^ Jedna z największych bomb II wojny światowej odnaleziona w Świnoujściu [One of the largest bombs of World War II found in Świnoujście], Onet, 20 September 2019
  36. ^ "Polish divers tackle massive British WW2 bomb in Baltic". BBC News. 12 October 2020. Retrieved 14 October 2020.
  37. ^ "'Earthquake' bomb explodes during defusing attempt". BBC News. 13 October 2020. Retrieved 14 October 2020.
  38. ^ a b "Navy begins defusing biggest World War II bomb ever found in Poland". CNN. Reuters. 13 October 2020. Retrieved 14 October 2020. The bomb was found in the Piast Canal which connects the Baltic Sea with the Oder River, and was dropped by the RAF in 1945 in an attack on the German cruiser Lutzow and had failed to detonate. The site is near the town of Swinoujscie in northwest Poland where a liquefied natural gas (LNG) terminal was opened in 2016.
  39. ^ "Poland's largest WW2 bomb explodes during attempt to defuse it". BBC News. 14 October 2020. Retrieved 15 October 2020.
  40. ^ Gunston 1979, p. 119.
  41. ^ McGowan 1988, pp. 64–68.
  42. ^ Dennis R. Jenkins (2008). Magnesium overcast: the story of the Convair B-36. North Branch, MN: Specialty Press. p. 144 photograph. ISBN 978-1-58007-129-1.

References

(June 1944

, July 1944 , August 1944 , September 1944 , October 1944 ,November 1944 , December 1944 , January 1945 , February 1945 , March 1945 , April and May 1945)

Further reading