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Mechanical Failure
Investigation of the possibility that a mechanical failure might have been the cause of the accident was made extremely difficult by the condition of the airplane when it was found after the accident. It was in thousands of pieces.
The condition of the engines indicates that they were operating at very high speed at the time of impact but the amount of power being developed is unknown. The switches and the fuel valves were found in the "on" position (the throttles were in the full open position but it cannot be determined in what position they were at the time of the impact). The bends in the propeller blades were identified by experts as power bends and witnesses near the scene of the accident testified that they heard a loud roar of engines immediately prior to the sound of the crash.
An inspection of the engines revealed no indication of a mechanical failure prior to impact. The condition of the master rod bearings and crank pins of both engines showed that the oil film had broken down and the parts showed signs of overheating as did some of the knuckle pins. However, in view of the completely separate lubrication systems and the identical character of the damage to both engines, it appears that the damage was caused not by mechanical failure of the engines but by some factor inherent in the attitude or motion of the airplane after the initial difficulty and previous to the crash.
The evidence indicates that the condition of the master rod bearings, the crank pins, and knuckle pins could result only from a momentary interruption of the oil supply to the bearings or from an overloading of the bearings either of which might have been caused by over-revving of the engines.[1]
- ↑ Over-revving is a condition which occurs when the engine speed exceeds the revolutions at which its governor is set. The maximum speed at which the governor is permitted to be set is the rotative speed which the engines are permitted to attain at takeoff, in this case 2350 rpm.
