The Palomares “Broken Arrow” Nuclear Bomb Accident

In 1966, the US Strategic Air Command lost four nuclear weapons over Spain when a B-52 bomber collided with a tanker plane.

The two recovered nuclear bomb casings from the Palomares incident, on display at the Museum of Nuclear Science and History in Albuquerque.

In the early 1960s, the Cold War was raging. The US and USSR had already faced off several times in Berlin and Korea, and in 1962 over the Cuban Missile Crisis. 

The Air Force’s Strategic Air Command (SAC), fearing a Russian surprise nuclear attack, devised a secret plan that was designated “Operation Chrome Dome”. Under Chrome Dome, a number of B-52 bombers would be kept in the air at all times–in shifts of six flights per day–to keep them safe in the event of a sudden Soviet attack that would destroy SAC’s airbases. These aircraft would be loaded with combat-ready nuclear weapons and would fly a circling pattern over areas near the USSR (like Alaska, Greenland, and the Mediterranean) for hours at a time, ready to penetrate Soviet airspace at a moment’s notice and deliver their weapons to pre-assigned targets.

On January 17, 1966, two B-52G bombers from the 51st Bomb Squadron, using the callsigns Tea 12 and Tea 16, took off from the Seymour Johnson SAC Air Force Base base in North Carolina and set out across the Atlantic. Their mission was to fly a Chrome Dome patrol around the Mediterranean and then return to the US.

Each of the B-52s carried four B-28 thermonuclear weapons. This was one of the most numerous nuclear bombs in the American arsenal, having been introduced in 1958. The B-28 was 22 feet long and weighed around 2000 pounds. It was a two-stage hydrogen bomb which used an implosion fission “Python” device as a primary trigger and a secondary  core of lithium deuteride as a fusion stage. The bomb was produced in various versions, known as “Mods”: the tactical version, known as Mod Y2, had no secondary stage and used only the fission trigger, giving a yield of 70 kilotons. The most powerful was the Mod Y5, with a yield of 1.45 megatons–around a hundred times more powerful than the Hiroshima bomb. Tea 12 and Tea-16 were carrying the Mod Y2 version, which had a yield of 350 kilotons.

The bomb was usually fitted with a parachute package at the tail end which slowed its descent, allowing the bomber enough time to safely get away from the explosion, and could be configured for either an airbust or for detonation on the ground. About 4500 B-28 weapons were manufactured between January 1958 and May 1966, and they remained in active service until 1991, making them one of the most ubiquitous of SAC’s nuclear arsenal.

The trip across the Atlantic was uneventful, and upon reaching Europe the two crews settled in for the standard “racetrack” patrol around the Mediterranean. At  9am Zulu Time (all SAC flights worldwide operated under Zulu Time no matter where they were–in this area the local time was about one hour ahead of Zulu Time) the two B-52s rendezvoused off the southeast coast of Spain with two KC-135 tanker aircraft, callsigns Troubadour 12 and Troubadour 14, from the Torrejon Air Base just outside of Madrid. This routine air-to-air refueling would gas up the B-52s for their long trip back to North Carolina.

The first indication that something was wrong came when the fuel boom operator on Troubadour 12 saw an explosion some distance away from him and then spotted what looked like a section of wing spinning down through the air. The pilot of Troubadour 12 then tried to contact Troubadour 14 by radio, and got no response. Descending from 31,000 to 4,000 feet, the pilot was able to see flaming wreckage on the ground, and what looked like a broken tail section from a B-52. One of the B-52s, Tea 16, had collided with the tanker Troubadour 14. According to some survivor accounts, the B-52 had come in too fast, hit the tanker, and sprayed both planes with fuel which then ignited.

The collision had happened over the Spanish coast, near the tiny village of Palomares. Almost immediately, a flood of reports began coming in to Spanish authorities from villagers who had seen the collision, as well as from several Spanish and British ships in the area. There were a number of reports of parachutes and survivors. All four of the KC-135 crew had been killed in the collision, but four of the seven crew on board the B-52 had parachuted from the plane. The radar operator came down on land, where he was met by Spanish civilians and taken to a local hospital. The others, which included the pilot, co-pilot and instructor pilot, came down in the sea where they were picked up by Spanish fishing boats.

Although the B-52s had become a familiar sight as they flew their patrols, the US Air Force and SAC had always been tight-lipped about the fact that these flights were combat-ready and were carrying thermonuclear weapons. Spain and the US had an agreement that allowed the bombers to carry live nukes, but it was decided for reasons of politics to hide that fact from the civilians–and in several areas of the world the US was carrying nuclear weapons without the knowledge of the local governments. American policy was, therefore, a strict “no comment” when it came to who was carrying H-bombs and where.

But now SAC faced a dilemma. The bomber that crashed at Palomares had been carrying four combat-ready B-28 nuclear weapons, and nobody knew what had happened to them. Furthermore, word had already gotten out to the world at large that the crash had involved nuclear weapons. As soon as Air Force officials at Torrejon learned of the accident, they sent a “Broken Arrow” report to SAC HQ in Nebraska, and SAC swung into action. A team of experts from Los Alamos was immediately dispatched from the United States, while Major General Delmar Wilson was sent from Torrejon to take charge of the crash scene.

Once it was confirmed that all of the surviving crew members had been accounted for, the most vital priority was finding the nukes. By that afternoon, search teams had been organized using Air Force personnel from Europe and the US, who were gathered in a spot near the crash zone that became known as “Camp Wilson”.

Just before dark, they found the first bomb, less than 1000 feet away from the crashed B-52. Riding down on its parachute, it had landed gently on a sandbank and rolled down onto the beach, perfectly intact but for a few dents and dings. A team from Los Alamos was on hand to “render-safe” the device by switching off the internal electronics.

Early the next morning, the second bomb was found. This bomb had not deployed its parachute, and unlike the first weapon the conventional explosives in the second bomb’s primary fission stage had detonated on impact. Although this could not set off a nuclear explosion, the conventional explosives had blown a crater 20 feet wide and 6 feet deep, and had sprinkled bits of the bomb components over 100 yards away. The plutonium core had also been pulverized and had scattered radioactive material over a significant area.

The third bomb, found about an hour later just outside of Palomares, had also detonated its conventional explosives on impact when the parachute didn’t open, creating another crater and another site of radioactive contamination. This was a much bigger explosion, tossing pieces of the bomb up to 500 yards away.

At all three sites, the Air Force put up a cordon of military guards to seal everything off and began cleanup operations. First, specialists from Los Alamos and the military’s Explosive Ordnance Disposal teams gathered up all of the bomb wreckage.  To deal with the radiation produced by the bomb’s plutonium, it was decided to scrape up all of the soil and vegetation from the contaminated areas, pack them into barrels, and ship them to the United States where they would be disposed of in designated hazardous nuclear waste dumps. The effort took over three months and involved several thousand men, costing some $80 million. In all, some 5000 55-gallon drums full of contaminated soil were removed from an area of 560 acres and shipped to the US.

But there still remained the problem of the missing fourth bomb. One witness, Spanish fisherman Francisco Simo Orts, had already reported seeing an object dangling from a parachute that had landed in the water, and the Air Force analysis of the crash confirmed that this was probably the bomb. (Orts later tried, unsuccessfully, to sue the Air Force for a substantial cash payment as “salvage rights” for finding the bomb.)

This was a situation that the US was not prepared for, however. In 1966, while the Navy had several experimental mini-subs and diving teams, deep-sea technology was still pretty primitive, and no one had ever attempted to locate and recover something as small as a nuclear weapon from the sea floor. For a time there was serious talk of just abandoning the nuke wherever it was, but political considerations made this impossible, and it was also feared that the Soviets might somehow find a way to retrieve the bomb. So, the Navy and Air Force conducted a massive joint operation to find the lost B-28.

A fleet of 20 ships was assembled as “Task Force 65” and sent to the search area, and the operation was given the codename “AIRCRAFT SALVOPS MED”. It included minesweepers, frigates, and support ships, as well as tender craft for a slew of experimental manned submersibles (including the Alvin and Aluminaut mini-subs) and remotely-operated vehicles (ROVs). The shallower areas of the search grid were examined by Navy divers, while the deeper areas were swept by sonar and by photographic ROVs. Meanwhile, Navy warships prevented a number of Russian trawlers from getting too close. The press presented a bigger issue, and while SAC tried its best to control the information that got out, the incident quickly made headlines all over the world.

The searchers were hampered by a lack of accurate charts for the area, as well as by heavy silt on the sea floor. Although the sonar could penetrate the silt and the murky water, it was not able to identify any objects that it found, so each sonar contact had to be painstaking examined by a diver or by a photographic ROV to confirm its identity–and there were hundreds of sonar contacts, any of which could have been the lost bomb. It was a slow process.

On March 1, sonar discovered a long straight contact almost 400 feet long, in the area where witnesses had seen the bomb descend. When the submersible Alvin was sent to investigate, the crew found a deep furrow that had been ploughed into the bottom silt at a depth of around 2000 feet. This ran to the edge of an underwater cliff, which dropped steeply to greater depths. At this point Alvin had to resurface to charge her batteries, and it took until March 15, after several tries, to relocate the furrow and follow it over the cliff. There, at a depth of 2500 feet, lay an object that was enshrouded in a parachute, and although it could not be conclusively identified visually, “Contact Number 261” was believed to be the bomb. It was perched precariously on a 70-degree slope.

Alvin then made two attempts to attach a line to the bomb so it could be lifted: both failed. Next, an anchor was lowered from the Navy ship Mizar and attached to the bomb, but the lines broke and the bomb fell further down the undersea cliff to a depth of 2800 feet. Finally on April 6 a series of lines was successfully attached to the bomb and it was raised to the surface.

Today, the area of the crash site is owned by the Spanish Government’s energy department and is off-limits to visitors. Plutonium contamination can still be found in the area, however, and the US continues to monitor the health of residents of Palomares.

The dented casings from the two recovered Palomares bombs are on exhibit at the National Museum of Nuclear Science and History in Albuquerque NM. The Aluminaut submersible submarine that was used in the search is on display at the Science Museum of Virginia, in Richmond.

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