Lake Central Flight 527

On 5 March 1967, Lake Central Flight 527 was scheduled from Chicago, Illinois to Detroit, Michigan. The flight, operated by one of the company's Convair 580 aircraft, left Chicago at 1704H and proceeded normally to Lafayette, Cincinnati, and Columbus. No problems were reported.

The aircraft was serviced in Columbus, and departed at 1952 hours for Toledo. At 2005 hours the flight was cleared by air traffic control to descend from 10,000 feet to 6,000 feet as it approached Toledo. Air traffic control requested that the flight report its descent, and to report crossing 8,000 and 7,000 feet. The crew acknowledged leaving 10,000 feet. This was the last transmission from the aircraft.[1]

Witnesses in the vicinity of Marseilles, Ohio reported hearing sounds from an aircraft at times between 2005 hours and 2010 hours. Some reported sounds like an engine "revving up". Shortly thereafter the sound of an explosion was reported.

By 2100H the authorities had confirmed that an aircraft had crashed in the area. Rain mixed with snow was reported at the time of the accident.

The aircraft was found to be loaded within normal limits, and the crew was found to be properly qualified for the flight, with no deficiencies reported.[1]

The aircraft was equipped with a flight data recorder. It was able to be read, having sustained no damage in the crash. Approximately 14 minutes after departing Columbus, the aircraft was on a heading of 322 degrees, when it abruptly veered right 40 degrees, and then left 55 degrees, at which point power to the recorder was abruptly terminated.[1] The cockpit voice recorder lost power at the same time, though right before power loss a sound described by investigators as "the first few seconds of an air raid siren" was heard.[1]

The aircraft had crashed in a farm field, on a heading of 360 degrees. The front fuselage had been separated from the main part of the aircraft, and debris was recovered from a 1.5 mile long, 1/2 mile wide trail on a heading of 135 degrees from the main wreckage. The right propeller was completely detached from the engine, as were the blades. In reconstructing the wreckage, the investigators revealed that the right propeller had separated in-flight and severed the fuselage.[2]

During manufacture, propeller pistons, which control the pitch of the propellers, are coated through a process called nitriding, which hardens them and makes them more resistant to surface wear.[3][4] They are supposed to be inspected to make sure the process is completed. While it is not known why the propeller on N73130 was not nitrided or failed inspections, the fact remains that it was, and was installed on N73130.[1] During the life of the engine, the piston had been slowly wearing away. During the flight, the piston finally failed, causing the propeller to over-speed. The propeller subsequently failed due to overstress, 1 to 2 seconds later. When the propeller failed, the blades were hurled through the cabin, severing control cables as well as the structural integrity of the plane itself. The investigators determined that the crash was solely caused by the propeller defect and subsequent failure.[1]

• A detailed explanation of the propeller failure
• Photo of N73130