
The B43 was a
United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
air-dropped
variable yield thermonuclear weapon
A thermonuclear weapon, fusion weapon or hydrogen bomb (H-bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a lowe ...
used by a wide variety of
fighter bomber and
bomber aircraft.
The B43 was developed from 1956 by
Los Alamos National Laboratory
Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development Laboratory, laboratories of the United States Department of Energy National Laboratories, United States Department of Energy ...
, entering production in 1959. It entered service in April 1961. Total production was 2,000 weapons, ending in 1965. Some variants were parachute-retarded and featured a
ribbon parachute.
The B43 was built in two variants, Mod 1 and Mod 2, each with five yield options. Depending on version, the B43 was in diameter, and length was between and . The various versions weighed between . It could be delivered at altitudes as low as , with
fuzing options for airburst, ground burst, free fall, contact, or
laydown delivery. Explosive yield varied from 70
kiloton
TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion. A ton of TNT equivalent is a unit of energy defined by convention to be (). It is the approximate energy released in the det ...
s of
TNT to 1
megaton of TNT.
The B43 used the
Tsetse primary design for its fission stage, as did several mid- and late-1950s designs.
The B43 was one of four thermonuclear gravity bombs carried by Canadian
CF-104 jets while serving in Germany between June 1964 and 1972.
Delivery systems

Carrier aircraft included most
USAF
The United States Air Force (USAF) is the Air force, air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its ori ...
,
USN and
USMC fighters, bombers and attack aircraft, including the
A-3 Skywarrior
The Douglas A-3 Skywarrior is a jet propulsion, jet-powered strategic bomber that was developed and produced by the Douglas Aircraft Company. It was designed by Douglas on behalf of the United States Navy, which sought a aircraft carrier, carr ...
,
A-4 Skyhawk,
A-5 Vigilante,
A-6 Intruder,
A-7 Corsair II,
B-47 Stratojet
The Boeing B-47 Stratojet (Boeing company designation Model 450) is a retired American long- range, six-engined, turbojet-powered strategic bomber designed to fly at high subsonic speed and at high altitude to avoid enemy interceptor aircraft ...
,
B-52 Stratofortress
The Boeing B-52 Stratofortress is an American long-range, subsonic aircraft, subsonic, jet-powered strategic bomber. The B-52 was designed and built by Boeing, which has continued to provide support and upgrades. It has been operated by the ...
,
B-58A Hustler,
F-100 Super Sabre,
F-105 Thunderchief
The Republic F-105 Thunderchief is an American fighter-bomber that served with the United States Air Force from 1958 to 1984. Capable of Mach 2, it conducted the majority of strike bombing missions during the early years of the Vietnam War. It ...
,
F-4 Phantom II,
F-104 Starfighter,
FB-111A strategic bomber variant,
F-15E Strike Eagle,
F-16 Fighting Falcon
The General Dynamics F-16 Fighting Falcon is an American single-engine supersonic Multirole combat aircraft, multirole fighter aircraft originally developed by General Dynamics for the United States Air Force (USAF). Designed as an air superio ...
and the
F/A-18 Hornet
The McDonnell Douglas F/A-18 Hornet is an all-weather supersonic, twinjet, twin-engine, carrier-based aircraft, carrier-capable, Multirole combat aircraft, multirole combat aircraft, designed as both a Fighter aircraft, fighter and attack airc ...
. The
B-1B Lancer
The Rockwell B-1 Lancer is a supersonic variable-sweep wing, heavy bomber used by the United States Air Force. It has been nicknamed the "Bone" (from "B-One"). , it is one of the United States Air Force's three strategic bombers, along with t ...
was also intended to carry the B43, though it remains unclear whether this particular aircraft was ever type-approved to carry the B43 prior to the B-1's reassignment to conventional strike roles. The B43 was also supplied for delivery by
Royal Air Force
The Royal Air Force (RAF) is the Air force, air and space force of the United Kingdom, British Overseas Territories and Crown Dependencies. It was formed towards the end of the World War I, First World War on 1 April 1918, on the merger of t ...
Canberra
Canberra ( ; ) is the capital city of Australia. Founded following the Federation of Australia, federation of the colonies of Australia as the seat of government for the new nation, it is Australia's list of cities in Australia, largest in ...
and
Valiant aircraft assigned to NATO under the command of SACEUR.
Broken Arrow
The B43 was never used in combat, but it was involved in a
nuclear accident
A nuclear and radiation accident is defined by the International Atomic Energy Agency (IAEA) as "an event that has led to significant consequences to people, the environment or the facility." Examples include radiation poisoning, lethal effect ...
when an
A-4E Skyhawk, BuNo ''151022'', of the (from Attack Squadron
VA-56), was lost off the coast of
Japan
Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
on 5 December 1965 when it rolled off an elevator, in of water in the Pacific Ocean, from
Kikai Island,
Kagoshima Prefecture
is a Prefectures of Japan, prefecture of Japan located on the island of Kyushu and the Ryukyu Islands. Kagoshima Prefecture has a population of 1,527,019 (1 February 2025) and has a geographic area of 9,187 Square kilometre, km2 (3,547 Square m ...
,
Japan
Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
.
The Skyhawk was being rolled out of the number 2 hangar bay, onto the number 2 elevator, when it continued over the edge and was lost. Neither the pilot LTJG
D. M. Webster, airframe, nor the bomb were ever recovered. No public mention was made of the incident at the time and it would not come to light until a 1989
US DoD report revealed that one of these one-megaton bombs (which had recently been retired from service and replaced) had gone missing. Japan then asked for details of the incident.
[Washington, D.C.: ]The Washington Post
''The Washington Post'', locally known as ''The'' ''Post'' and, informally, ''WaPo'' or ''WP'', is an American daily newspaper published in Washington, D.C., the national capital. It is the most widely circulated newspaper in the Washington m ...
, "''Japan Asks Details On Lost H-Bomb''", Wednesday, 10 May 1989, page A-35.
Withdrawn
The B43 was phased out in the 1980s, and the last B43 weapons were retired in 1991 in favor of the newer
B61 and
B83 weapons.
See also
*
List of nuclear weapons
References
External links
Allbombs.html data page at nuclearweaponarchive.orgVideo showing shipboard handling procedures for the B43 bomb
{{United States nuclear devices
Cold War aerial bombs of the United States
Nuclear bombs of the United States
Military equipment introduced in the 1960s