[2][3] The aircraft, a B-52G, was based at Seymour Johnson Air Force Base in Goldsboro, and part of the Strategic Air Command's airborne alert mission known as "Cover All" (a predecessor to Operation Chrome Dome), which involved a continuous flow of staggered, nuclear-armed bombers on a "ladder" route into the Canadian Arctic and back.

During the hook-up, the tanker crew advised the B-52 aircraft commander, Major Walter Scott Tulloch, that his B-52 had a fuel leak in the right wing.

However, when it reached its assigned position, the pilot reported that the leak had worsened and that 37,000 pounds (17,000 kg) of fuel had been lost in three minutes.

[8] The crew's final view of the aircraft was in an intact state with its payload of two Mark 39 thermonuclear bombs still on board, each with yields of 3.8 megatons.

The aircraft wreckage covered a two-square-mile (5.2 km2) area of tobacco and cotton farmland at Faro, about 12 miles (19 km) north of Goldsboro.

[10][11] Explosive ordnance disposal (EOD) teams from Seymour Johnson and other bases arrived on the scene quickly, disarming the one bomb that was easily accessible.

[7] The two bombs involved in the Goldsboro accident were Mark 39 Mod 2 thermonuclear weapons with a maximum predicted yield of 3.8 megatons of TNT equivalent.

The pit of the primary was entirely composed of enriched uranium ("all-oralloy"), with no plutonium, and was a sealed-pit, meaning that it was fully-assembled at all times.

To make sense of their analysis and the controversies, it is first necessary to understand what the normal firing sequence of a Mark 39 Mod 2 used in combat conditions would be.

Prior to normal use, the "safing pins" would need to be pulled out of the bomb horizontally, which could be done by the crew in the cockpit by means of a lanyard that was connected to them.

The retraction of the arming rods would also close valves sealing a reference chamber in the MC-832 Differential Pressure Switch, a barometric fuze for detecting the bomb's altitude.

[17] Upon receiving this current, the MC-788 would then connect the (not yet-charged) high-voltage thermal battery to the X-Unit, the electrical device that provides a high voltage signal to the detonators used in the "primary" stage of the weapon.

[c] After the timing circuit completed its countdown of 42 seconds, it would then deliver initiation power to the MC-641 High Voltage Thermal Battery pack.

[13][20] At some point in the above sequence, not indicated in declassified documents (possibly because of its classified nature), "squibs" on the Los Alamos Laboratory 1A Valve Mechanism would fire and cause the gas from the boost reservoir to be injected into the "primary" of the bomb.

For a free-fall delivery, it would need to be released at least 35,000 feet (11,000 m) above the target, or else it would hit the ground prior to the timer circuit completing its countdown and the X-Unit being charged.

This switch was found by the initial explosive ordnance disposal (EOD) team on the scene to be in the "Safe" position,[27] and did not pass its current on further.

[28] The weapon was found in an upright position, with its parachute hanging on adjacent trees, about one mile (1.6 km) behind where the main wreckage of the aircraft impacted.

[29] On January 24, the EOD team from Wright-Patterson Air Force Base disassembled and "safed" the weapon (by disconnecting the tritium reservoir from the primary), and returned it to Seymour Johnson AFB.

1 "underwent a normal release sequence in which the parachute opened and the components of the weapon which were given an opportunity to actuate by the pulling of the Bisch rods did behave in the manner expected.

1] in the Goldsboro accident had experienced inadvertent operation of its ready-safe switch prior to breakup of the aircraft, a nuclear detonation would have resulted.

'"[34] Charlie Burks, another nuclear weapons systems engineer for Sandia, also added: "Unfortunately, there have been thirty-some incidents where the ready/safe switch was operated inadvertently.

In 2013, Lt. Jack ReVelle, an EOD officer on the scene, recalled the moment: "Until my death I will never forget hearing my sergeant say, 'Lieutenant, we found the arm/safe switch.'

Pumps were used to remove water, and the sides of the crater were reinforced with plywood, but it was decided after digging down to 42 feet (13 m) to abandon the effort.

[31]Another analysis by Sandia engineers in 1961 concluded that while in both weapons the MC-772 Arm/Safe Switch operated "as it was designed to do," the lanyard-controlled safing-pins "cannot be relied upon to prevent initiation of the fuzing sequence" in this kind of accident, and recommended implementing a modification to the weapons "as rapidly as possible" that would prevent the fuze power supply from activating except when live release was intended.

[46] A 1969 analysis by Sandia supervisor Parker F. Jones concluded that the Goldsboro accident illustrated that "the Mk 39 Mod 2 bomb did not possess adequate safety for the airborne alert role in the B-52.

2, because its timer had not run out by the time it impacted the ground, it could not have detonated even if its Arm-Safe Switch had been set to "Arm", as its thermal batteries had not charged, and they would be needed to fire the weapon.

Political scientist Scott Sagan has used this as an example of "what appears to be the complete disappearance of a number of B-52 airborne alert accidents from the command's organizational memory" and indicative of "the depth of SAC's reluctance to acknowledge such problems.

According to declassified meeting notes, McNamara "went on to describe crashes of US aircraft, one in North Carolina and one in Texas[g], where, by the slightest margin of chance, literally the failure of two wires to cross, a nuclear explosion was averted.

[55] In 1962, the landowner was paid $1,000 to grant the United States of America a perpetual 200-foot (61 m) radius circular easement over the remains of the buried second bomb.

The terms of the easement: ... convey unto the Grantee, the United States of America and its assigns, a perpetual and assignable easement for the establishment, maintenance and operation of a restricted area in, upon, over and across the land described herein, consisting of: In July 2012, the State of North Carolina erected a historical road marker in the town of Eureka, 3 miles (4.8 km) north of the crash site, commemorating the crash under the title "Nuclear Mishap".