Air University Review, March-April 1967
Dr. William S. Coker
On 5 March 1948 a U.S. Air Force B-29 Superfortress dropped the world’s
largest conventional bomb on the test range at Muroc AFB,
The size and weight of bombs have always been limited by the capability of aircraft
to carry them. In January 1945, with the prospect of getting the B-36 into
production before the war ended, the Army Air Forces requested the Ordnance
Department to develop a bomb not larger than 60 inches in diameter nor longer
than 322 inches. The B-36 was expected to be able to carry a 72,000-lb payload
4600 miles, or an even heavier load over shorter distances.4 After
some preliminary work Ordnance advised that a bomb meeting those specifications
and weighing about 42,000 pounds could be built. Within a few months an order
for 100 of the bombs was placed with the A.O. Smith Corporation of
These bombs never enjoyed a nickname or fancy title such as those given the British earthquake bombs, Tall Boy and Grand Slam. The Milwaukee Journal once referred to the 44,000-pounder as an “extra-super-blockbuster,” but the name never caught on. Thus, the largest bomb ever made was destined to go through life with the ordinary nomenclature “Bomb, General Purpose, 42,000-lb., T12.” One slight change did occur, however, when after three years the Ordnance Committee decided to redesignate it “Bomb, General Purpose, 44,000-lb., TI2.” In part, this was done because the bomb was overweight. Changes in fabrication had added a few pounds, and the finished product weighed in excess of 43,000 pounds. Later changes in tail fins and filler material even caused weight differences between individual bombs. The new nomenclature, it was asserted, was also to save confusion, since the bombs had been variously referred to as 42,000-lb, 43,000-lb, and 44,000-lb bombs.6
The idea for such mammoth bombs originated with Dr. B. N. Wallis of
Vickers-Armstrongs (Aircraft) Ltd. Wallis, a noted aircraft designer, became
interested in huge bombs early in the war. He had hit upon the idea of
Wallis had also developed the principle of the so-called earthquake bomb,
which was designed to bury itself in the ground close to its objective, the
subsequent underground explosion creating an effect similar to an earthquake.
The 12,000-lb Tall Boy was the first of the earthquake bombs produced. Its bomb
blast was so great that it “caused entire buildings to disintegrate and
collapse into rubble.”8 The Tall Boy was first used on the night of
8 June 1944 when 19 of them were dropped on the Saumur railway tunnel. One
direct hit caused the roof of the tunnel to fall in. By the end of the war in
Europe, 854 Tall Boys had been dropped on concrete submarine pens, E-boat
bases, and V-weapon sites, as well as other targets in
The success of the Tall Boy and the need for an even larger bomb led to the
development of its big brother, the 22,000-lb Grand Slam. Great secrecy
surrounded the manufacture of the Grand Slam, and the company that made the
casing labeled it a “boiler.” This subterfuge apparently fooled no one, for in
the pubs around
The Army Air Forces, which had never used the big earthquake bombs, by late
1944 began to see their possibilities. They could be employed as
general-purpose bombs for blast and fragmentation effect, to create cave-ins
and earth shock, and to get at important underground installations. In addition
to the development of the T10 and T14, the
The B-36 was test-flown for the first time in August 1946. Even then the first models of the B-36 could not carry the big bomb, and it would be some months before they could be modified to handle it. The Air Force, which was interested in experimenting with the 44,000-lb bomb, decided that a modified B-29 could handle the job until a B-36 was available.
Toward the end of the war a B-29 had been converted to carry two 22,000-lb
bombs, one under each wing, for use against
The aircraft chosen for the alterations was a B-29A, No. 44-62263. The
In addition to the modification of the B-29, a special bomb lift had to be built to handle the 44,000-lb missile. The Boeing Company designed a 50,000-lb lift that would hoist a 25-ton bomb 12½ feet in the air, roll it 360 degrees in either direction, shift it 4 inches either side of center and 10 inches fore or aft, and tilt it 6 degrees up or down. One man operating six levers could load one of the bombs into an aircraft. 15
Squadron C, 608th AAF Base Unit, Chemical & Ordnance Test Group,
stationed at Muroc, was selected to drop the first TI2.16
Preparations for the drop continued throughout the fall of 1947 and early 1948.
After modification, the Superfortress and its crew were sent to Eglin AFB,
The Superfort reached Muroc in December, and the 50,000-lb lift arrived the
following month. A series of minor problems then delayed the actual drop for
some time. The lift had been damaged en route to
Just before noon on 5 March 1948, the bomb was released from B-29 No. 2263, piloted by Captain William A. Looney. The Group historian recorded the event in these words, “On this date the heaviest bomb the world has ever known, weighing 43,755-lbs was dropped from a B-29 aircraft from an altitude of 25,000 feet. The entire mission was highly successful and the bombing results were excellent.”18 By 19 April 1948 the personnel of Squadron C and B-29 No. 2263 were veterans, having dropped six of the extra-super blockbusters.19 Their part in the operation was completed.
The use of a B-36 to drop the bomb after it had already been dropped by the much smaller B-29 would almost have been an anticlimax except for one thing: the B-36 dropped two of them on the same mission. On 29 January 1949 at Fort Worth, Texas, Consolidated Vultee B-,36 No. 43, piloted by Major Stephen P. Dillon, carried the greatest bomb load ever lifted to that date into the sky—over 43 tons. The weight lifted was equivalent to that of a B-17 Flying Fortress. Including bombs and fuel, the B-36 grossed over 300,000 pound—not startling in terms of today’s behemoths, but in 1949 it was a whopping amount. 20
The two bombs were flown by the B-36 from
All these T12 bombs dropped were unarmed. Eventually the bomb was exploded, but the details have not yet been released. The results of the first explosive-filled 22,000-lb Grand Slam dropped by the British produced a crater 30 feet deep and 124 feet in diameter. It is readily evident that the 44,000-lb Tl2 could produce a sizable earthquake.22
One advantage of the T12 over an atomic bomb is obvious: If the military situation called for heavy blasting of large areas through which our men would eventually have to advance, the 44,000-lb bomb could be used without having to worry about radiation contamination from an exploded A-bomb. The Air Force has also recognized its possibilities in creating cave-ins and earth shock and in getting at important underground installations. Dropping a string of the extra-super blockbusters in areas of known Viet Cong subterranean strongholds might just force them to give up such positions, bringing the enemy to the surface and into the open where more conventional and less expensive methods and weapons could do the trick.
1. AF press release, 10 March 1948. The press release called it a 21-ton bomb, but it weighed 43,755 pounds.
2. Constance McLaughlin Green, Harry C. Thomson, and Peter C. Roots, The Ordnance Department: Planning Munitions for War, a volume in the U.S. Army in World War II, The Technical Services series (Washington: Government Printing Office, 1955), p. 451.
3. AF press release, 10 March 1948; Paul Brickhill, The Dam Busters (London: Evans Bros., Ltd., 1951), p. 31.
4. Major J. A. Swaney, “Record of Army Ordnance Research and Development, Bomb Development,” p. 370; Wesley Frank Craven and James Lea Cate (eds.), The Army Air Forces in World War II (7 vols.; Chicago: University of Chicago Press, 1948-1958), VI, 245.
5. Swaney, “Bomb Development,” p. 370; R. J. Kastenholz, A. O. Smith Corp. to Chief of Ordnance, Attn: Col. C.H.M. Roberts, 8 June 1949, AF Historical Division, Archives, Maxwell AFB, Alabama.
6. Clipping from Milwaukee Journal, 12 October 1945; memorandum from Col. C. H. M. Roberts to the Secretary, Ordnance Technical Committee, 13 May 1949.
7. Brickhill, p. 31 et passim. In 1963 Dr. Wallis explained the details of the weapon and the strategy employed in its use in an unpublished article entitled “The ‘Dam Busting’ Weapon.” A copy of this study was provided the author by Vickers-Armstrongs (Aircraft) Ltd.
8. Green, et al., pp. 470-71.
9. Charles Webster and Noble Frankland, The Strategic Air Offensive
Against Germany (4 vols.;
10. Brickhill, pp. 249-52.
11. Webster and Frankland, III, 203-4.
12. Swaney, p. 370; Green, et al., pp. 454, 471.
13. The Fat Man, the plutonium-type atomic bomb, was exploded over
14. AF press release, 10 March 1948; Unit History, Squadron C, 608th AF Base Unit, Muroc AFB, California, semiannual summary, March 1948, file 240.07608, AF Archives.
15. AF press release, 10 March 1948; Boeing Plane Talk, No. 15, 5 August 1949.
16. History, Squadron C, July 1947.
17. History, Squadron C, December 1947, January-March 1948.
18. Historical Record, 608th AFBU, Phillips Field, Aberdeen Proving Ground, Maryland, 1 January-30 June 1948, p. 15.
19. The bombs were dropped on 5, 10, 12, 18, and 22 March and 19 April 1948. History, Squadron C, March and April 1948.
22. Webster and Frankland, III, 203-4.
Illustrations accompanying this article are used with kind permission of the
Dr. Williams S. Coker (Ph.D.,
The conclusions and opinions expressed in this
document are those of the author cultivated in the freedom of expression,
academic environment of
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