Modern replica of a Tallboy
|Place of origin||United Kingdom|
|In service||8 June 1944 - 25 April 1945|
|Used by||No. 617 Squadron RAF|
|Wars||World War II|
|Weight||5,443 kg (12,000 lb)|
|Length||6.35 m (21 ft)|
|Diameter||950 mm (38 in)|
|Filling weight||2,358 kg (5,200 lb)|
|No. 58 fuse - built from No. 30 Pistol (impact detonation) - or No. 47 time delay fuze. Fuses were inserted into tetryl boosters.|
The Tallboy or Bomb, Medium Capacity, 12,000 lb, was an earthquake bomb developed by the British aeronautical engineer Barnes Wallis and deployed by the RAF in 1944. It weighed five tons and, carried by the Avro Lancaster, was effective against hardened structures against which earlier, smaller bombs had proven ineffective.
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 tons, which would fly at 320 mph (510 km/h) at 45,000 feet (14,000 m) to carry the heavy bomb over 4,000 miles (6,400 km), but the Air Ministry were against a single-bomb aircraft, and the idea was not pursued beyond 1942.
Following Wallis' 1942 paper Spherical Bomb — Surface Torpedo and the design of the "bouncing bomb" for the Dam Busters of Operation Chastise, the design and production of Tallboy was done without a contract on the initiative of the Ministry. As such, the RAF were using bombs they had not bought and that were still the property of the manufacturer, Vickers. This situation was normalised once their capabilities were recognised.
Accomplishments of the Tallboy included the 24 June 1944 Operation Crossbow attack on La Coupole — along with Grand Slams — 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 feet (18 m) below the surface.
Most large Allied World War II aircraft bombs had very thin skins to maximize the weight of explosive a bomber could carry—this was an improvement on the early part of the war, when the explosive content of British bomb designs was low.
To be able to penetrate the earth (or hardened 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 very aerodynamic, so that when dropped from a great height it would reach a terminal velocity much higher than traditional bomb designs.
In the final design, the tail of the bomb was about half the overall length of the finished weapon—the bomb casing was some 10 feet (3 m) of the overall 21-foot (6 m) length. Initially the bomb had a tendency to tumble, so 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, improved the aerodynamics and improved accuracy.
Tallboy was designed to be dropped from an optimal altitude of 18,000 feet (5,500 m) at a forward speed of 170 miles per hour (270 km/h). Impacting at 750 miles per hour (1,210 km/h), it made a crater 80 feet deep (24 m) and 100 feet (30 m) across and could go through 16 feet (5 m) of concrete.
The weight of the Tallboy (approximately 12,000 lb) 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. Even then the Lancaster was not capable of reaching the bomb's intended dropping height of 40,000 ft (12,200 m) but only around 25,000 (7,700 m).
At the same time No. 617 "Dambusters" Squadron trained in the use of a special bombsight, the Stabilizing Automatic Bomb Sight (SABS). For accuracy, multiple corrections had to be made for temperature, wind speed, and other factors. It was only effective if the target could be identified, and several missions were cancelled or unsuccessful because of difficulty in accurately identifying and marking the targets.
For use on underground targets, the bomb was fitted with three separate inertia 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, a total of three separate 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 fuses failed to function, the third would trigger detonation. Despite this elaborate system, at least one Tallboy failed to explode during the second attack on the Sorpe dam and was found during repairs in late 1958 when the reservoir was emptied.
Although the bomb was aimed at the target during an operation, and proved capable of penetrating deep into hardened reinforced concrete when it hit, this was not the primary intention of Barnes Wallis's design. The bomb was designed to impact close to the target, slide into 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 immediate surroundings, with the blast dissipating rapidly through the air. An earthquake impact shook the whole target, and caused major structural damage to all parts of it, making repair uneconomic. The attack reports below should be considered with this in mind.
The construction of each Tallboy was labour intensive because each was largely hand-made, requiring much manual labour during each separate manufacturing stage. The materials used were costly, with very precise engineering requirements with regard to casting and machining. For example, to increase penetrative power, a large and 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 machined into a perfectly symmetrical shape to ensure optimum aerodynamic performance. This was no easy task when manipulating a bomb casing with the size and weight of a Tallboy.
The Torpex filling was poured into the base of the upturned casing by hand, 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-inch layer of woodmeal-wax composite with three cylindrical recesses fitted with the explosive boosters and into which (when the bomb was finally armed), a total of three chemical time-fuses were inserted.
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.
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.
June - August 1944
- Saumur rail tunnel — The sole operational north-south route on the Loire. Nineteen Tallboy-equipped and six conventionally equipped Lancasters of 617 Squadron attacked on the night of 8/9 June 1944. This was the first use of the Tallboy bomb and the line was destroyed — one Tallboy bored through the hillside and exploded in the tunnel about 60 ft (18 m) below, completely blocking it. No aircraft were lost during the raid.
Operation Crossbow sorties
Operation Crossbow was a set of offensive and defensive measures that were carried out to deal with the threat of the German V-1 flying bomb ("buzz bomb" or "doodlebug") and V-2 rocket weaponry. As part of the operation, a number of sorties using Tallboys were deployed by the British to destroy several missile sites.
- 19 June 1944 - Watten
- The nearest Tallboy dropped by 617 Squadron landed 50 yards (46 m) from the target, a heavily fortified V-2 launch site under construction The bunker was rendered useless.
- 24 June 1944 - Wizernes
- The target was a V-2 assembly and launch site linked with the Watten site. Several Tallboy hits undermined the foundations but did not penetrate the dome. The bunker was abandoned.
- 25 June 1944 - Siracourt V-1 bunker
- Lancasters of 617 Squadron scored three direct hits with Tallboys without loss.
- 4 July 1944 - Saint-Leu-d'Esserent
- 617 Squadron used seventeen Lancasters with Tallboys, supported by one Mosquito and one Mustang, in an attempt to collapse the limestone roof of the caves used as storage depots. Aircraft from No 5 Group followed up with 1,000 lb (450 kg) bombs.
- 6 July 1944 - Mimoyecques
- Tallboys hit one of the V-3 cannon's shafts and blocked galleries with earth and debris
- 17 July 1944 - Wizernes
- Sixteen Lancasters, led by a Mosquito and a Mustang, bombed Wizernes -- three Lancasters managed to drop Tallboys (one caused the dome to shift out of alignment, two others blocked the entrance.
- 27 July 1944 - Watten
- One Tallboy hit the target but did not penetrate the structure.
- 31 July 1944 - Rilly La Montagne
- Both ends of the railway tunnel were collapsed by Tallboys dropped by 617 Squadron. William Reid's Lancaster at 12,000 ft (3,700 m) was hit by a Tallboy dropped from 18,000 ft (5,500 m)
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 1944 - Le Havre
- Part of the first massive RAF daylight raid since the end of May 1943, two waves attacked E-boat facilities at Le Havre: No 1 Group first, No 3 Group second. Just before the first wave, 22 Lancasters of 617 Squadron and 3 Mosquito marker aircraft attacked, several hits were scored on the pens, one bomb penetrated the roof.
- 15 June 1944 - Boulogne harbour
- 297 aircraft - 155 Lancasters, 130 Halifaxes, 12 Mosquitos - of Nos 1, 4, 5, 6 and 8 Groups attacked Boulogne harbour. One Halifax was lost. A French report described the great destruction as the worst raid on Boulogne.
- 5 August 1944 - Brest
- 15 Lancasters of 617 Squadron attacked the U-boat pens at Brest and scored six direct hits with Tallboys penetrating the concrete roofs. One Lancaster was shot down by flak. Subsequent attempts to reinforce other sites with even thicker concrete diverted resources from other projects.
September - November 1944
- Dortmund-Ems Canal near Ladbergen, north of Münster – 617 Squadron scored six direct hits with Tallboys on the night of 23/24 September 1944.
- Kembs Dam north of Basle — The dam waters could have been kept in reserve to flood the area of a US advance. On 7 October 1944, the Dambusters destroyed the lock gates with Tallboys dropped at low level, releasing the stored water.
- Sorpe dam — This target of the original Dambusters raid survived a second attack by 9 Squadron on 15 October 1944 (617 Squadron did not participate in this raid). The Tallboy bombs were seen to hit the dam but did not breach it.
Bombing sorties against Tirpitz
The German battleship Tirpitz was a threat against convoys sailing to and from the Soviet Union.
- Operation Paravane, 15 September 1944
- One Tallboy hit near the bow of the Tirpitz and caused considerable damage. The shock-wave from the hit damaged the battleship's engines, causing the Germans to convert the ship into a semi-static heavy artillery battery.
- Operation Obviate, 29 October 1944
- No direct hits were scored but one near miss bent a propeller shaft.
- Operation Catechism, 12 November 1944
- In the final operation the Tirpitz was sunk when two Tallboys hit her and four others fell close by. The battleship rolled over and capsized in shallow water.
December 1944 - April 1945
- Bombing of U-boat pens, December 1944-April 1945
- IJmuiden, 15 December 1944
- Flight Lieutenant Thomas Clifford Iveson dropped one Tallboy.
- IJmuiden, 12 January 1945
- Bergen, 12 January 1945
- 32 Lancasters and one Mosquito of Nos 9 and 617 Squadrons attacked U-boat pens and shipping in Bergen harbour. Three Lancasters of 617 Squadron and one from 9 Squadron were lost; the Germans told the local people that 11 bombers had been shot down. A local report said that three Tallboys penetrated the 3½-metre-thick roof of the pens and caused severe damage to workshops, offices and stores inside.
- IJmuiden & Poortershaven 3 February 1945
- 36 Lancasters of No 5 Group attacked U-boat pens at IJmuiden (9 Squadron) and Poortershaven (617 Squadron) with Tallboys. Hits were claimed on both targets without loss.
- Hamburg, 9 April 1945
- 617 Squadron attacked with Tallboys and Grand Slams. Some of the bombs hit their target and no aircraft were lost.
- Heligoland, 18 April 1945
- 969 aircraft - 617 Lancasters, 332 Halifaxes and 20 Mosquitos of all groups bombed the naval base, airfield and town "almost into crater-pitted moonscapes". Three Halifaxes were lost; the islands were evacuated the following night.
- Heligoland, 19 April. 36 Lancasters used Tallboy bombs against coastal positions
The Urft Dam, (30 miles south west of Cologne) was attacked on 8 December and 11 December 1944 to prevent it being used to flood the area as American troops advanced. The lip of the dam was damaged, but the Germans prevented further damage by lowering the water level.
The Bielefeld and Arnsberg viaducts were attacked by 617 and 9 squadrons with Tallboys and the first Grand Slams on 14 March 1945. The Arnsberg viaduct withstood the attack but 100 m of the Bielefeld viaduct collapsed through the 'earthquake effect' of the Grand Slams and Tallboys. The Arnsberg viaduct was attacked again on 15 March 1945 by 9 Squadron, it did not collapse.
The pocket battleship Lützow was attacked on 16 April 1945 by 617 Squadron. Despite intense flak, 15 aircraft managed to bomb the target with Tallboys or with 1,000-pounders. One near miss with a Tallboy tore a large hole in the bottom of the Lützow and she settled to the bottom in shallow water. One Lancaster was shot down, the Squadron's last loss of the war.
Hitler's vacation home, Berghof, near Berchtesgaden was attacked on 25 April 1945 with a mixed force that included six Lancasters of 617 Squadron dropping their last Tallboys. The bombing appeared to be accurate and effective.
Use by the United States
The T-10 was an American-made version of the 12,000 lb Tallboy modified to use standard American components. Development was started in late 1944 and plans were made to drop them on the fortified island strongholds of the Pacific to aid in softening their defences before amphibious assaults. None were ever used in combat, 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 used to destroy railroad bridges and reservoir dams, being dropped by the B-29 Superfortress.
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 completely assembled M-121 and they 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. During the Vietnam War, some M-121s, minus their rear streamline shroud and tail fin assembly were shipped to Vietnam for Commando Vault missions where the warhead was dropped by C-130 using radar control. The warhead was mounted on a platform and pulled by a parachute from the rear loading ramp of the C-130. After clearing the aircraft the large extraction chute and pallet were cut away and small triangular chute stabilized the large warhead till impact. A three-foot nose probe detonated the bomb at the right stand-off. 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 famous Battle of Hamburger Hill. Dropping from 10,000 feet, 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.
Notes and references
- Bombs Weapons Rockets Aircraft Ordnance
- "Saumur Tunnel, 9th June 1944". Royal Air Force Bomber Command 60th Anniversary. Ministry of Defence/Deltaweb International. Retrieved 2007-05-24.
- Ellis, John (1998). One Day in a Very Long War. Jonathan Cape. p. 297. ISBN 9780224042444.
- "Campaign Diary". Royal Air Force Bomber Command 60th Anniversary. UK Crown. Retrieved 2007-05-24. 1944: June, July, August, September, October, November, December 1945: January, February, March, April
- "June 1944 Campaign diary". Royal Air Force Bomber Command 60th Anniversary. UK Crown. Retrieved 2007-05-24.
- Irving, David (1964). The Mare's Nest. London: William Kimber and Co. p. 245.
- Collier, Basil (1976) . The Battle of the V-Weapons, 1944-1945. Yorkshire: The Emfield Press. pp. 68, 84. ISBN 0-7057-0070-4.
- Brickhill, Paul (1951). The Dam-busters. Apogee Books Space Series 36. New York: Thomas Y. Crowell. ISBN 0-330-37644-6.
- "Dambusters - The raid on Wizernes Rocket Base".
- "World War II German hardened A4/V2 rocket launch sites". Retrieved 2008-02-17.
- "Flight Lieutenant William Reid VC". News. Telegraph Media Group Limited 2008. 29 November 2001. Retrieved 2008-02-17.[dead link]
- The reference for Boulogne does not indicate Tallboy bombs were used.
- Keable, Jim. "Flight Lieutenant Thomas Clifford Iveson". AeroVenture News. AeroVenture. Retrieved 2008-02-24.
- "Tirpitz, 12 November 1944". Royal Air Force Bomber Command 60th Anniversary. UK Crown. Retrieved 2007-05-24.
- Ziemke, Earl Frederick (1960). The German Northern Theater of Operations 1940-1945. US Government printing office, p. 311. OCLC 1249014
- RAF Campaign Diary -- April and May 1945
- 617 Squadeon - The Operational Record Book 1943 - 1945 (pdf) with additional information by Tobin Jones; Binx Publishing, Pevensey House, Sheep Street, Bicester. OX26 6JF. Acknowledgement is given to HMSO as holders of the copyright on the Operational Record Book. Page 507
- Iain Murray [Big & Bouncy: The Special Weapons of Barnes Wallis], 2005. Quotes Alan W. Cooper; From the Dams to the Tirpitz, 1982 (Goodall), and Alan W. Cooper; The Men Who Breached the Dams, 1982 (Kimber)
- Memorabilia signing and veterans day at Lincolnshire Aviation Heritage Centre East Kirkby South Yorkshire Aircraft Museum 29 August 2005. See Flight Lieutenant Thomas Clifford Iveson. The Campaign Diary does not indicate Tallboy bombs were used on this mission.
- Rockets & Guided Missiles p. 119 by Bill Gunston, Salamander Books Ltd, ISBN 0-517-26870-1
- Note: The B-52 bomb bay lacked the length required to load it.
- Mission Commando Vault by Sam McGowan (USAF-ret.) Air Combat October 1988 p. 64-68 ISSN 0044-6955
- The use of any type or make of the Tallboy ended with the Vietnam War. None were dropped during the Gulf War in 1991 as none were in storage for the USAF. The huge bomb dropped by C-130s during the Gulf War in 1991 was the 15,000 lb type BLU-82.
|Wikimedia Commons has media related to: Tallboy bomb|
- Barnes Wallis Trust
- A picture of a Lancaster carrying a Grand Slam
- Article about the defusing of the unexploded Tallboy in the Hamburger Abendblatt (German)
- "Huge Bomb Drills Into Target Before Exploding." Popular Mechanics, February 1945, p. 49.