1963 Elephant Mountain B-52 crash

On 24 January 1963 a United States Air Force Boeing B-52C Stratofortress with nine crew members on board lost its vertical stabilizer due to buffeting stresses during turbulence at low altitude and crashed on Elephant Mountain in Piscataquis County, Maine, United States, 6 mi from Greenville. The pilot and the navigator survived the accident.

Accident

One hour later, around 2:30 p.m. the Stratofortress crossed the Princeton VOR, descended to 500 ft and started its simulation of penetrating enemy airspace at low altitude with an airspeed of 280 kn. The outside temperature was -14 F with winds gusting to 40 kn and 5 ft of snow on the ground.

Approximately 22 minutes later, just after passing Brownville Junction in the center of Maine, the aircraft encountered turbulence. When the pilot and crew commander, Westover's Most Senior Standardization Instructor Pilot, started to climb above it, the vertical stabilizer came off the plane with a "loud noise sounding like an explosion". Having suffered severe damage, the B-52C went into a 40-degree right turn, with nose pointed downward. The pilot gave the order to abandon the aircraft when he could not level it.

Only the upper flight deck crew members of the B-52C have ejection seats that eject them upwards. The seats of the pilot, copilot, and electronic warfare officer (a navigator also trained in electronic warfare) function at any altitude, as long as the airspeed is at least 90 kn, which is the minimum required to inflate their blast propelled parachutes. The lower-deck crew members eject on a downward track. Hence, the navigator and radar navigator cannot safely eject at altitudes less than 200 ft. Spare crew members do not have an ejection seat at all. They must use parachutes and either jump out of the navigators' hatch after the navigators have ejected or drop out of the aircraft's door. The tail gunner has his own unique escape option: he can sever the tail gun and jump aft out the resulting hole in the rear.

The navigator, who was operating as electronic warfare officer, ejected first. He was followed by the pilot and the copilot; there was neither enough altitude nor time for the six lower-deck crew members to escape before the aircraft crashed into the west side of Elephant Mountain at 2:52 p.m.

The copilot suffered fatal injuries, striking a tree 1 mi away from the main crash site. The pilot landed in a tree 30 ft above the ground. He survived the night, with temperatures reaching almost -30 F, in his survival-kit sleeping bag atop his life raft. The navigator's parachute did not deploy upon ejection. He impacted the snow-covered ground before separating from his ejection seat about 2000 ft from the wreckage with an impact estimated at 16 times the force of gravity. He suffered a fractured skull and three broken ribs. The force bent his ejection seat and he could not get his survival kit out. He survived the night by wrapping himself in his parachute.

A grader operator on a remote woods road witnessed the final turn of the Stratofortress and saw a black smoke cloud after impact. Eighty rescuers from the Maine State Police, the Maine Inland Fish and Game Department, the Civil Air Patrol, as well as Air Force units from Dow Air Force Base in Bangor, Maine, along with others from New Hampshire and Massachusetts and other volunteers, went to work. Search aircraft were on the scene, but they searched too far south and east to locate the wreckage before nightfall.

After the crash site was located the next day, Scott Paper Company dispatched plows from Greenville to clear 10 mi of road of snow drifts up to 15 ft deep. The rescuers had to use snowshoes, dog sleds and snowmobiles to cover the remaining mile to the crash site. At 11 a.m. the two survivors were airlifted to a hospital by a helicopter.

Accident investigation

The crash was caused by turbulence-induced structural failure. Due to buffeting stresses, the stabilizer shaft broke and the B-52's vertical stabilizer came off the plane. It was found 1.5 mi from where the plane struck the mountain side. With the loss of the vertical stabilizer, the aircraft had lost its directional stability and rolled uncontrollably.

Originally, the B-52 was designed to penetrate Soviet airspace at high altitude around 35000 ft and high speed around 450 kn to drop nuclear weapons. When the US intelligence realized that the Soviets had implemented a sophisticated, layered and interconnected air defense system with radar controlled surface-to-air missiles (SAMs), the US Air Force decided the B-52 would have to penetrate the Soviet airspace at low altitude (around 500 ft) and high speed to stay underneath the radar. However, low altitude, high speed flight operations put enormous stress on an aircraft's structure, especially when flying near mountains, up and down ridges and through valleys due to lee waves. The B-52 was not designed for this kind of operation. 56-0591, a B-52D, took off from Larson AFB, Washington, on 23 June 1959 and experienced a horizontal stabilizer turbulence-induced failure at low level and crashed. The modification process of the B-52 series began in 1961.

B-52C 53-0406, which crashed on Elephant Mountain, was the second high-tailed B-52 to suffer such a fatal structural failure. After extensive testing and another three similar failures (two with fatal crashes) within 12 months of the Elephant Mountain crash, Boeing determined that turbulence would over-stress the B-52's rudder connection bolts, causing first a rudder and subsequently a tail failure. The bolts were strengthened throughout the fleet, fixing the problem.