Accident at Hollywood, South Carolina, 17 Dec 1955

Accident narrative

On December 17, 1955, a Riddle Airlines Curtiss-Wright C-46F crashed in a cornfield near Hollywood, South Carolina, southwest of Charleston. The aircraft was destroyed by impact and fire, and both pilots—the only occupants—were killed. At approximately 2040, witnesses heard engines and saw lights descending on an erratic path as the aircraft fell to the ground in several pieces.

**The flight** The aircraft was operating as scheduled cargo Flight 207B, having departed Idlewild Airport, New York, at 1557 for Miami, Florida, with scheduled stops in Wilmington, North Carolina, and Jacksonville, Florida. It carried a cargo of dress goods and first-class mail. The pilots were Captain George Albert Lohr, who had logged 10,000 hours including 731 in C-46 aircraft, and Copilot Richard John Glendon, who had 3,300 hours. Both held airline transport ratings.

Flying on a VFR flight plan, the aircraft landed at Wilmington at 1857 and departed again at 1936. It was loaded to a gross weight of 47,994 pounds, just under the 48,000-pound maximum, with the load properly distributed.

At 2003, the flight reported its position over Myrtle Beach radio. This transmission was intercepted by Captain Norman Crull, who was flying northbound near Charleston in another Riddle C-46. Direct radio contact was established between the two captains. Captain Lohr asked about surface winds, ground speed, and other conditions encountered by Crull en route from Miami, but made no comment about having any difficulty. Crull, flying at 7,000 feet, concluded that Lohr's interest in surface winds indicated he was flying at a low altitude of 2,000 to 4,000 feet. Following a routine position report to Charleston Radio at 2032, no further radio contact was made with Flight 207B.

**What the investigation found** Weather observations at Charleston recorded unlimited ceilings, seven miles of visibility, and calm winds.

Wreckage was distributed over an area approximately 2,500 feet north to south and 700 feet east to west, proving that disintegration occurred at an appreciable altitude. The right wing, vertical fin, and both horizontal stabilizers had separated in flight. The main wreckage—consisting of the fuselage, wing center section, right engine, landing gears, and left wing—fell almost vertically. The left engine nacelle separated from the wing and was found 312 feet south of the main wreckage. Examination of the engines and propellers revealed no indication that they had malfunctioned.

Analysis of the structural damage indicated that the lower surface of the right outer wing panel buckled under high compressive loads, and the wing bent downward before the upper surface failed. Portions of the separated right wing then struck the tail surfaces, causing them to fail. The Board concluded that the downward failure of the right wing from excessive aerodynamic loads was the first event in the sequence of structural failures. The left engine nacelle failure occurred late in the sequence and was likely caused by abnormal inertia loads resulting from uncontrolled gyrations after the wing and tail surfaces separated.

Because the weather did not include the strong vertical air movements necessary to cause such loads, the Board ruled out gusts. The Board noted that excessive negative loads on the wing during cruising flight are likely to result from either failure or erratic operation of the horizontal tail surfaces.

According to company records, the aircraft had flown a total of 1,304 hours, with 304 hours since its major overhaul and conversion from a military C-46A to a civil C-46F. It had been abandoned in the Egyptian desert before being acquired by Officine Aeronavali of Venice, Italy, which converted it for Riddle Airlines. The investigation revealed that Curtiss-Wright had not supplied a complete set of drawings for the conversion. Where specified materials were unavailable, Aeronavali used substitute materials, and many newly installed parts were heavier than the originals.

Examination of the recovered tail components disclosed numerous nonconformities. The spring-loaded elevator Vee tab shaft assembly bound due to variations in dimensions and a bowed shaft. The left elevator spring tab cartridge contained two concentric springs instead of the specified single spring, and wear marks indicated they interfered with each other. The push-pull tubes for the elevator spring tabs had symmetrical clevises instead of offset ones, causing misalignment.

Company flight logs showed pilot complaints of "porpoising" and stiffness in the elevator tab controls on several dates in late November and December. Maintenance entries recorded a check of the elevator tab rigging, a change of tension on the Vee tab rod, and, on December 15, the replacement of the right and left elevator spring cartridges.

The Board found that these nonconformities made the airplane ineligible for airworthiness certification. A CAA-designated aircraft maintenance inspector in Venice had issued a standard cargo airworthiness certificate but inserted the comment "Subject to final engineering approval." The recertification form was erroneously executed and not processed in a manner that brought it to the attention of CAA Engineering. When Riddle made further alterations to fit the aircraft into its fleet in Miami, the need to check conformity was overlooked. The Board found that both the CAA and Riddle Airlines should have detected the nonconformities.

Although flutter was ruled out, the Board believed that the cumulative effects of the nonconformities could have caused sufficient erratic action of the tabs to pitch the airplane nose-down and produce excessive negative loads on the wing.

**Probable cause** The Board determined that "the probable cause of this accident was an inflight structural failure resulting from a violent pitch-down induced by the erratic action of nonconforming elevator tab controls."