1958 Tybee Island mid-air collision

1

A Mk 15 nuclear bomb of the type lost when jettisoned after the collision
Midair Collision summary
Date	February 5, 1958
Summary	Midair collision
Site	Tybee Island, Georgia, United States 32°0′N 80°51′W
First aircraft
Type	Boeing B-47
Operator	United States Air Force
Registration	51-2349
Fatalities	0
Second aircraft
Type	F-86 Sabre
Operator	United States Air Force
Crew	1
Survivors	1

The Tybee Island B-47 crash was an incident on February 5, 1958, in which the United States Air Force lost a 7,600-pound (3,400 kg) Mark 15 nuclear bomb in the waters off Tybee Island near Savannah, Georgia, United States. During a practice exercise, the B-47 bomber carrying the bomb collided in midair with an F-86 fighter plane. To protect the aircrew from a possible detonation in the event of a crash, the bomb was jettisoned. Following several unsuccessful searches, the bomb was presumed lost somewhere in Wassaw Sound off the shores of Tybee Island.

Midair collision

Crash site

Atlanta

Georgia

The B-47 bomber was on a simulated combat mission from Homestead Air Force Base in Florida. It was carrying a single 7,600-pound (3,400 kg) bomb. At about 2:00 AM, the B-47 collided with an F-86. The F-86 crashed after the pilot ejected from the plane, but the B-47, although damaged, remained airborne, albeit barely. The crew requested permission to jettison the bomb in order to reduce weight and prevent the bomb from exploding during an emergency landing. Permission was granted, and the bomb was jettisoned at 7,200 feet (2,200 m) while the bomber was traveling at about 200 knots (370 km/h). The crew did not see an explosion when the bomb struck the sea, and managed to land the B-47 safely at the nearest base, Hunter Air Force Base. The pilot, Colonel Howard Richardson, was awarded the Distinguished Flying Cross after this incident.

Bomb

Some sources describe the bomb as a functional nuclear weapon, but others describe it as disabled. If the bomb had a plutonium nuclear core installed, it was a fully functional weapon. If the bomb had a dummy core installed, it was incapable of producing a nuclear explosion but could still produce a conventional explosion. The 12-foot (4 m) long Mark 15 bomb weighs 7,600 pounds (3,400 kg) and bears the serial number 47782. It contains 400 pounds (180 kg) of conventional high explosives and highly enriched uranium. The Air Force maintains that the bomb's nuclear capsule, used to initiate the nuclear reaction, was removed before its flight aboard B-47. As noted in the Atomic Energy Commission "Form AL-569 Temporary Custodian Receipt (for maneuvers)", signed by the aircraft commander, the bomb contained a simulated 150-pound cap made of lead. But according to 1966 Congressional testimony by then Assistant Secretary of Defense W.J. Howard, the Tybee Island bomb was a "complete weapon, a bomb with a nuclear capsule," and one of two weapons lost by that time that contained a plutonium trigger. Nevertheless, a study of the Strategic Air Command documents indicates that in February 1958, Alert Force test flights (with the older Mark 15 payloads) were not authorized to fly with nuclear capsules on board. Such approval was pending deployment of safer "sealed-pit nuclear capsule" weapons that did not begin deployment until June 1958.

Recovery efforts

Starting on February 6, 1958, the Air Force 2700th Explosive Ordnance Disposal Squadron and 100 Navy personnel equipped with hand held sonar and galvanic drag and cable sweeps mounted a search. On April 16, the military announced the search had been unsuccessful. Based on a hydrologic survey, the bomb was thought by the Department of Energy to lie buried under 5 to 15 feet (2 to 5 m) of silt at the bottom of Wassaw Sound.

In 2004, retired Air Force Colonel Derek Duke claimed to have narrowed the possible resting spot of the bomb to a small area approximately the size of a football field. He and his partner located the area by trawling in their boat with a Geiger counter in tow. Secondary radioactive particles four times naturally occurring levels were detected and mapped, and the site of radiation origination triangulated. Subsequent investigations found the source of the radiation was natural. In any case, a Geiger counter is not efficient in detecting alpha radiation from enriched uranium, because of the minimal ability of alpha particle to penetrate water (a few millimeter at most).

Ongoing concerns

The risk of corrosion of the bomb's alloy casing is lessened if it is completely covered in sand. But if part of the casing is exposed to seawater due to the shifting strata in which it is buried, rapid corrosion could occur, as demonstrated in simulation experiments. Eventually, the highly enriched uranium could leach out of the device and enter the aquifer surrounding the continental shelf in that area. Storms, hurricanes, and strong currents frequently shift the sand there.

To date, no undue levels of unnatural radioactive contamination have been detected in the regional Upper Floridan aquifer by the Georgia Department of Natural Resources (over and above the already high levels thought to be due to monazite, a locally occurring sand naturally high in radiation).

This event, as well as the 1956 B-47 disappearance, were the basis for NCIS Episode "Broken Arrow," which aired in 2010.

See also

• Broken Arrow
• List of military nuclear accidents
• List of nuclear accidents
• 1950 British Columbia B-36 crash

References

• "Air Force Search & Recovery Assessment of the 1958 Savannah, GA B-47 Accident". Air Force Nuclear Weapons and Counterproliferation Agency (PDF). 12 April 2001. http://www.af.mil/shared/media/document/AFD-060726-022.pdf. Retrieved 27 February 2010. 
• Shaughnessy, Larry (September 13, 2004). "Lost Bomb". USA. CNN. http://www.cnn.com/2004/US/09/13/lost.bomb/. Retrieved 5 February 2008. 
• Bell, Brett (14 September 2004). "Savannah NOW". http://www.savannahmorningnews.com/stories/091404/2441929.shtml. Retrieved 15 September 2004. 
• Carter, Chelsea (3 May 2004). "The Seattle Times". http://seattletimes.nwsource.com/html/nationworld/2001918347_hbomb03.html. Retrieved 15 September 2004. 
• Welsh, Edward (21 August 2001). "Common Dreams News Center". Archived from the original on 13 October 2004. http://web.archive.org/web/20041013161922/http://www.commondreams.org/views01/0821-05.htm. Retrieved 16 September 2004. 
• Michael H. Maggelet and James C. Oskins, "Broken Arrow: The Declassified History of U.S. Nuclear Weapons Accidents". ISBN 978-1-4357-0361-2.

External links

• Tybeebomb.com, Informational site about the Tybee Bomb
• America's Lost H Bomb, Marabella Productions & Discovery's Science Channel documentary about the Tybee Bomb (2007)
• NPR, For 50 Years, Nuclear Bomb Lost in Watery Grave (3 February 2008)
• BBC News, Missing for 50 years - US nuclear bomb (22 June 2009)
• The Nuclear Information Project, Nuclear Bomb Dropped in Georgia; No Nuclear Capsule Inserted, Documents Show (2004)
• Strategic-Air-Command.com, Chart of nuclear bombs, including the Mark 15
• Chasing Loose Nukes by Col. Derek Duke (as told to Fred Dungan)

* [http://www.bbc.co.uk/programmes/b00l55xm BBC.co.uk], BBC audio programme on the Tybee Bomb, streaming audio<--->