Skip to main content

“Aircraft 53-1876A Has Lost A Device”

June 2024
13min read

How the U.S. Air Force came to drop an A-bomb on South Carolina

On the afternoon of March 11, 1958, the Gregg sisters—Helen, six, and Frances, nine—and their cousin Ella Davies, nine, were in the playhouse their father had built for them in the woods behind their house in Mars Bluff, South Carolina. About four o’clock they tired of the playhouse and moved 200 feet to the side yard. This kept them from becoming the first Americans killed by a nuclear weapon released on U.S. territory. U.S. Air Force B-47E medium bomber serial number 53-1876A dropped its nuclear weapon in the woods behind the Greggs’ house at 4:19 P.M. The high-explosive trigger in the bomb blew up on contact with the ground, leaving a crater 50 feet across and 35 feet deep and injuring the three girls. All that remained of the playhouse were a few twisted shards of the corrugated metal that had been its roof.

At 8:00 that morning Capt. Earl Koehler, pilot; Capt. Charles Woodruff, co-pilot; Capt. Bruce Kulka, navigator/bombardier; and crew chief Sgt. Robert Screptock had arrived at Hunter Air Force Base just outside Savannah, Georgia, to fly their B-47 in Operation Snow Flurry that afternoon. Snow Flurry was not routine training but rather part of a “Unit Simulated Combat Mission and Special [i.e., nuclear] Weapons Exercise.” Briefings for the mission had begun ten days before takeoff, and two generals had appeared to emphasize the exercise’s importance. Aircraft 53-1876A, accompanied by three other B-47s from the 375th Bombardment Squadron, was to carry a nuclear weapon to Bruntingthorpe Air Base, England, conducting a midair refueling en route off the east coast of Canada. Before landing, the crew was to make a practice bomb run over England, transmitting an electronic signal to simulate the bomb release. Computers on the ground were to determine the accuracy of the “drop” and award points accordingly. Had the mission been completed, the crew would have had a tense, exhausting 18-hour day.


The bomb

Nuclear weapons then, as now, contained a high-explosive trigger to compress a uranium/plutonium core to a critical mass and initiate the chain reaction of a nuclear explosion. Perhaps the single greatest trick in nuclear-weapons design is to focus the immense force of the trigger explosion onto the core with precisely the proper geometry, strength, and timing to compress it to the exact degree required by the laws of physics to start a chain reaction, rather than simply blow the bomb apart. There are two types of high explosives that could be used in the trigger. One could be set off by concussion, such as a bullet or contact with the ground; the other—the type the military today invariably insists upon—could take great physical abuse without going off. Unfortunately, the triggers used in nuclear weapons in 1958 contained the former.


The plane

The six-engine B-47 was the first modern jet bomber. The initial production model came out in March 1950; at more than 600 miles an hour, it was faster than any operational jet fighter in the world. It had a three-man crew with room for one passenger and was capable—barely—of crossing the Atlantic without refueling. On takeoff a fully loaded B-47 was virtually a flying gas tank, being just over 52 percent fuel by weight. But it could not dump its internal fuel tanks in an emergency, as could civilian airliners, and it wasn’t structurally strong enough to land safely with a large fuel load. When a fully fueled B-47 left the ground on takeoff, the choice was either to fly for several hours in order to burn off fuel or to crash. Nuclear weapons could add another 5,000 to 20,000 pounds, making the aircraft even harder to fly. Perhaps feeling some guilt over its failure to provide the B-47 with adequate safety features, the Air Force stipulated that on takeoff and landing the crew should be able to drop its nuclear weapon(s) promptly in an emergency, at least marginally improving the pilot’s ability to control the aircraft.

Nuclear weapons were held in a B-47 by two systems: a complicated but reliable pneumatically powered catch that could be operated by the crew and a manually inserted steel locking pin. With the locking pin in place, it was impossible to drop the weapon. With the pin out, the crew could jettison the weapon almost immediately. By regulation, the locking pin was to be out for landing and takeoff.


The Strategic Air Command (SAC) was founded in 1946 to provide a force capable of nuclear retaliation against the Soviet Union. In October 1948, Curds LeMay took over as commander. During World War II he had earned the unaffectionate title Iron Ass for what his airmen considered a fanatic devotion to training. In his bombing campaign against Germany, LeMay had developed a scheme of flying bombers in tight formations over enemy territory, thus permitting them to protect one another from enemy fighters. To improve bombing accuracy, he came up with the idea of “lead” navigation. Selected crews became highly familiar with the approach routes to specific targets, and the entire tightly grouped formation would drop its bombs when the lead plane did. LeMay’s revolutionary tactics became standard U.S. practice; but flying large bombers in tight formations for hours was not a natural act, and it took a great deal of work to develop the concentration to do it routinely.

Not surprisingly, LeMay brought the deep faith in training he developed during World War II to his new job at SAC. Virtually every aspect of the routines he devised was quantified, with points awarded for performance counting heavily in promotions. The results of particularly important activities, such as simulated combat missions like “Snow Flurry,” were relayed electrically to SAC headquarters, where senior officers, including the commander himself, reviewed them aggressively. If a mission did not go well, the local commander might receive a direct message from LeMay demanding a personal briefing on the reasons. Local commanders were, to say the least, anxious to avoid this.

Losing a “device”

The nuclear weapon that landed on Mars Bluff was a Mark 6 30-kiloton bomb, an older fission (nonhydrogen) design considered highly reliable. It weighed 7,600 pounds, was 10 feet 8 inches long, and had a maximum diameter of 61 inches. Starting at eight o’clock on the morning of March 11, a specialized two-man loading crew took one hour and seven minutes to put the bomb into Air Force 531876A. When the loading team had trouble engaging the steel locking pin, they called the weapons release systems supervisor for assistance. He took the weight of the weapon off the plane’s bomb-shackle mechanism, put it onto a sling, and then “jiggled” the pin with a hammer until it seated. The bomb was put back on the shackle, and preflight checks continued. But neither the bomb-loading crew nor the aircrew ran the locking pin through its engage/disengage cycle with the bomb’s weight on the shackle. For the crew to receive maximum points for its unit under the ground rules, all preflight checks had to be finished by 10:30. It is difficult not to suspect that institutional pressure to gain points led to omission of this step.

After the bomb had been loaded and the preflight checks completed, the crew went to briefings on weather and operations, had lunch, and returned to the plane about 2:40. At 3:42 Captain Koehler started his engines. At 3:51, as required by regulations, co-pilot Woodruff rotated his seat to face aft and pulled the lever to disengage the locking pin from the nuclear weapon. It could now be dropped instantly in case of an emergency. At 3:53 the plane took off to join three other B-47s for a formation flight to Europe. When the B-47 reached an altitude of 5,000 feet, Woodruff again rotated his seat, this time to re-engage the locking pin. He worked the locking lever unsuccessfully for five minutes as the B-47 climbed to 15,000 feet to join the three other aircraft. At this point, the crew knew it had a problem. The pilot told the bombardier, Captain Kulka, to go into the bomb bay to try to seat the locking pin by hand. This was not a trivial decision; the bomb bay was not pressurized, so the entire plane had to be depressurized. Because the plane was at 15,000 feet, the crew had to go on oxygen. Further complicating matters, the entrance to the bomb bay was so narrow that a parachute could not be worn into it. The task was doomed from the start; later testimony indicated Kulka had no idea where to find the locking pin in the large and complicated bomb-release mechanism. After a tense 12 minutes searching for the pin, the bombardier decided, correctly, that it must be high up in the bomb bay and invisible because of the curvature of the bomb. A short man, he jumped to pull himself up to get a look at where he thought the locking pin should be. Unfortunately, he evidently chose the emergency bomb-release mechanism for his handhold. The weapon dropped from its shackle and rested momentarily on the closed bomb-bay doors with Captain Kulka splayed across it in the manner of Slim Pickens in Dr. Strangelove. Kulka grabbed at a bag that had providentially been stored in the bomb bay, while the more-than-three-ton bomb broke open the bomb-bay doors and fell earthward. The bag Kulka was holding came loose, and he found himself sliding after the bomb without his parachute. He managed to grab something—he wasn’t sure what—and haul himself to safety. Moments later the plane was rocked by the shock wave of the blast when the bomb hit the ground.

Within seconds the more-than-three-ton weapon broke open the bomb-bay doors.

In case of an unscheduled bomb drop, Air Force regulations required the crew to immediately notify its base by a special coded message. Because the procedure had never been used, the operations center at Hunter Air Force Base did not recognize the strange incoming message. As a final indignity, the pilot was reduced to radioing an open, uncoded message to the civilian tower at the Florence airport six miles west of Mars Bluff asking them to advise Hunter by telephone that aircraft 53-1876A had lost a “device.” The plane then turned back to photograph the site with its aerial camera. This was not difficult; the plume of smoke was easily visible from nearly three miles up. Because the plane could not dump fuel, it descended to the denser air at 6,000 feet, where it circled for 2 hours and 26 minutes before landing uneventfully.

…And on the ground

The concussion from the explosion injured all five members of the Walter Gregg family (Mrs. Gregg was sewing in the front parlor, and her son, Walter Junior, was standing next to his father in the toolshed) as well as their cousin, Ella Davies. They were taken to the Florence hospital, where Ella, who had 31 stitches, was kept overnight and the others released. Although the Greggs certainly knew their problems stemmed from some sort of explosion, it was not until that evening at the hospital that Walter Gregg learned it was caused by a U.S. Air Force bomb.

The Florence Morning News knew the real cause of the problem several hours before Gregg did. The call came into the paper just before 5:00 P.M. and was taken by Thom Andersen, who would one day be the News ’s managing editor but who was then a cub sportswriter. He was the only reporter in the newsroom; the others were down the street at the courthouse attending a trial, and Anderson went there to tell his superiors about the explosion. They speculated that an external fuel tank had dropped and told him to check on it in the morning. Anderson, however, was not convinced, and he rounded up a freelance photographer and took off for Mars Bluff. They got a ride to the site with a senior Air Force officer who had just arrived and needed directions; their car was waved through hastily established checkpoints manned by the Civil Air Patrol and the state police. Anderson quickly discovered the actual nature of the explosion, the photographer got pictures of the crater and the wreckage of the house, and the next day the Morning News had four articles on the accident, with photographs, on its front page—substantially better coverage than The New York Times was able to give the event. In addition to the thrill of covering what was certainly the biggest story in the area in a decade, Anderson was flattered to field telephone inquiries about the incident from the foreign press. Things got even better for him when he received a number of checks from those news organizations, a pleasure previously unknown to Florence cub sports reporters.

The reception of the B-47 crew back at their base was perhaps more difficult than their flight. By regulation, all crew members on missions carried loaded pistols. As the crew clambered out of the aircraft, they were met by armed air police, who relieved them of their weapons and took them to a room in the base operations center with mattresses hastily arranged on the floor. They were told they would be obliged to stay here “at least overnight”; they were not allowed to contact their families or anyone else. The fear seems to have been that they had dropped the bomb deliberately. Later that evening, General LeMay, who was by then vice chief of staff of the Air Force, called Captain Koehler directly to get a telephone briefing on what had happened. LeMay, perhaps the only operational commander in the Air Force who had actually performed maintenance on his bombers, understood Koehler’s explanation, and the crew was released.


The accident was featured prominently in the national and international press. The New York Times’s columnist Harrison Salisbury commented, and the prime minister of Great Britain reassured the House of Commons. Overall, what is surprising is that coverage essentially disappeared after three days, and despite conflicting statements from the Air Force, the press did not investigate whether radioactive material had been released into the atmosphere. This casual acceptance stands in stark contrast to the media frenzy that accompanied the accident at Three Mile Island 21 years later. As it turned out, classified Air Force radiation studies released in 1997 indicate that radiation after the Mars Bluff explosion was barely above background levels. As was the rule in peacetime, the fissionable nuclear core of the weapon was stored elsewhere in the aircraft in what was called “the birdcage.” In a war situation, the crew would have transferred the nuclear core from the birdcage to the bomb bay and inserted it into the bomb.

Mars Bluff

Mars Bluff, South Carolina, is a rural community too small to have its own post office. It is not shown on either the Rand McNally road map of the United States or the one for South Carolina. One might suppose that a nuclear-weapon drop would be the only thing to distinguish it from thousands of similar places across the country. On the contrary. In 1993 the historian Amelia Wallace Vernon published African Americans at Mars Bluff, South Carolina , a distinguished, highly acclaimed book that documents the successful private cultivation of rice by slaves in Mars Bluff and their descendants into the twentieth century and develops persuasive evidence that the technical expertise to raise rice in South Carolina (and Louisiana) came from slaves brought over from middle Africa, where it was the staple crop. In her book Mrs. Vernon locates the rice fields carefully, and several are within a few hundred yards of where the bomb landed. Given the size of Mars Bluff, it is not too surprising that she is also a cousin of Walter Gregg.

Money…you think we owe you money?

When the bomb entered his back woods, Walter Gregg was a 37-year-old conductor with the Atlantic Coast Line Railroad. He had served in the Army as a paratrooper in World War II and married Ethelmae Helms, whom he met on a blind date in 1942. In January 1953 the Greggs moved into the house they built on land that had been in the Gregg family for more than a hundred years. They planned to live there permanently and built their house with a solid masonry foundation and cypress planking. In its own internal documents the Air Force describes the house as “House, Frame, 224 feet from impact point, extremely well constructed of first class material.”

Air Force officials said they would settle all claims “promptly and fairly,” and a senior legal officer was sent from the headquarters of the Air Materiel Command ostensibly to do this. This officer started by denying the Greggs a housing allowance; they had, he noted, moved in with Mr. Gregg’s brother on the night of the blast and thus were incurring no extra expense. He then moved briskly on to the Greggs’ property claims. In 1958 the Air Force paid claims to its own personnel only on the depreciated value of the damaged or destroyed item, not on the basis of its replacement cost. The claims officer applied this practice scrupulously to the Greggs and insisted they list every item damaged along with its date of purchase and original price. This included such items as Mrs. Gregg’s collection of cut glass inherited from her grandmother, her wedding presents, her crocheted tablecloths, and her collection of 70 china demitasse cups. The Greggs’ Chevrolet sedan was a total loss, and the Air Force provided a rental car for one week—enough time, the claims officer said, for the Greggs to process their insurance claim and buy another one. Satisfied it had protected its own honor and the interests of the taxpayers, the Air Force offered the Greggs a total of $44,000 for the destruction of their house, garage, toolshed, clothes, 6 to 14 chickens (the chickens were free-range, and some were vaporized in the explosion; the Air Force was reluctant to commit itself to a spécifie number without a body count), and everything else. The Greggs refused the offer and turned to their congressman for assistance. He sponsored a private bill permitting the family to sue the U.S. government. The bill was passed, President Eisenhower signed it, the Greggs retained a lawyer and sued the Air Force in federal court. Three years and three months after they’d been bombed, the Greggs finally received the amount the Air Force had originally offered, plus $10,000, from which they had to pay their legal expenses.


The Mars Bluff incident obliged the Air Force to make significant changes. The composition of the high explosive used in nuclear-weapon triggers was promptly reformulated. No longer would it be possible for the explosive trigger in a nuclear weapon to be set off by concussion; the new design required a specific electrical impulse. While the Air Force and the Department of Energy do not discuss such matters, it seems likely that the changes cost hundreds of millions of 1958 dollars. Also, within days of the accident, a regulation was published requiring that locking pins be inserted in nuclear-weapon bomb shackles at all times, including takeoffs and landings.

We may speculate how this incident might have “played” if it had happened in 2000. The relative equanimity with which the press and the residents of Mars Bluff greeted the accident would certainly not have been duplicated. The Air Force’s almost casually accepted assertion that only minuscule amounts of radiation had escaped would have been subjected to the greatest skepticism and rigorous checks by the press. We can also fairly assume that in the 1990s follow-up articles would have explored the Air Force’s parsimonious treatment of the Greggs’ claims. The public, given a chance to contemplate the matter on 60 Minutes , might have believed that the Greggs had a point when they claimed their losses fell beyond the confines of straight-line depreciation.

Where are they now?

After the bomb destroyed what was, really, their dream house, the Greggs gave up country living and moved to Florence, where they now live in a neat brick bungalow. The Air Force prohibited the crew from discussing the incident with the press while they remained on active duty, but members of the aircrew did travel to Florence individually to pay their respects to the Greggs. Mars Bluff seemed to have little, if any, negative effects on the crew members’ careers. Captain Koehler remained in the Air Force for 12 more years and retired as a lieutenant colonel; Captain Woodruff left for civilian life in 1959; Captain Kulka served 13 more years, retiring as a major; and Sergeant Screptock stayed on until 1982, retiring at the highest noncommissioned rank. In 1997 the Greggs sold the four-acre plot upon which their house had been built and where the bomb crater was located (they retain the rest of the adjacent land). The new owners are developing the parcel into a community of modular houses known as Francis Marion Forest. The crater, not greatly diminished, remains and can be seen about a hundred feet off Lucius Circle, at the one o’clock position as you enter the circle from the county road. In the late summer the crater is almost dry, but after the winter rains it fills within a foot or two of the top, a large but benign memento of the Cold War and a day when the press could actually underwhelm a subject.

Enjoy our work? Help us keep going.

Now in its 75th year, American Heritage relies on contributions from readers like you to survive. You can support this magazine of trusted historical writing and the volunteers that sustain it by donating today.