Flight Overview
The aircraft, N37512, a DC-6 operated by United Air Lines, departed New York International Airport at 1428 on a Visual Flight Rules flight plan. Captain S. C. Hoyt, the UAL New York area flight manager, was in command. Also on board were Captains V. H. Webb and H. M. Dozier, who were to receive their periodic instrument proficiency checks. The flight was scheduled to return to LaGuardia Airport after the checks.
At 1501, the crew reported to the company that they were "doing air work around Hempstead." A second message at 1527 indicated they intended to make an Instrument Landing System (ILS) approach at MacArthur Field in Islip. The flight contacted the MacArthur tower, which granted permission for an ILS approach and landing. A normal landing was made on runway 32.
Events at MacArthur Field
After landing, the aircraft taxied to the intersection of runways 28 and 32. The crew prepared for takeoff. Weather observations at 1532 showed scattered clouds at 20,000 feet, broken clouds at 25,000 feet, visibility over 15 miles, temperature 53°F, dew point 30°F, and wind from the north-northwest at 20 knots with gusts to 30 knots. The weather was similar to conditions when the flight departed.
At 1548, the MacArthur controller cleared the flight to take position on runway 32 and take off. The aircraft took the position but did not depart immediately, prompting a second clearance at 1550. The gross takeoff weight was approximately 61,050 pounds, well below the maximum allowable, and the load was correctly distributed.
Takeoff and Accident Sequence
The aircraft became airborne approximately 1,500 to 1,800 feet down the runway. The takeoff and initial climb appeared normal, with the aircraft maintaining runway heading. At about 50 feet above the ground, the right wing lowered and the aircraft began a right turn. The landing gear was retracting. The climbing turn continued, and the bank angle increased to nearly vertical by the time the heading changed about 90 degrees, at an estimated altitude of 150 feet. The nose then dropped sharply, and the aircraft dived into the ground, striking on the right wing and nose. It cartwheeled before coming to rest right side up. An intense fire ignited and consumed a large portion of the wreckage despite the prompt response of firefighting equipment.
Investigation Findings
The investigation found no evidence of failure or malfunction of the structure, powerplants, propellers, or electrical system. The probable cause was determined to be unintentional movement of the No. 4 throttle into the reverse range just before breaking ground, while the other three engines were at high power output. This rendered the aircraft uncontrollable shortly after becoming airborne. The crew had been simulating an engine-out instrument takeoff, and during power reduction to zero thrust, the No. 4 propeller was unintentionally reversed. Evidence indicated that the pilot attempted to move the No. 4 throttle forward to unreverse, but the reverse warning flag remained engaged, increasing reverse thrust. The combination of an outboard propeller in reverse on a DC-6 at takeoff configuration and airspeed, with high power on the other engines, led to immediate loss of control. There was insufficient time and altitude for corrective action.