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It appears that the condition of the bearings and crank pins indicates over-reviving immediately prior to impact and not mechanical failure within the engines themselves or their oil systems. An investigation was, nevertheless, made of the mechanical adjustment to the oil filter for the right engine which was required just prior to take-off of the airplane from Washington. As we have previously stated, the oil pressure as shown on the gauge for the right engine had fallen below normal and it was necessary to rotate the blades in the cuno oil filter to relieve it of any sediment which might be blocking the oil flow. It is not believed that the condition which required this mechanical adjustment had any bearing upon the accident or upon the condition of the engines prior to or after the crash. The accumulation of sediment on the oil filter discs to such an extent as to reduce oil pressure is not uncommon and the blades installed between each pair of discs are designed to remove this sediment. After the blades had been turned, the copilot stated that the oil pressure had returned to normal. Moreover, this adjustment was required only with respect to the right engine. Since each engine has an independent oil system, the low pressure on the right engine could not have had any effect upon the left engine. It is not unusual for sludge or sediment to appear in airplane engines making it necessary that filters be installed in the lubricating system to prevent sludge from being directed through the smaller passages throughout the engine which might cause lubrication failure with resultant serious damage or failure to the engine. The oil companies have made an extensive research in cooperation with the manufacturers of engines used in air carrier service, as well as the air carrier operations departments, resulting in only a high grade of oil being approved by engine manufacturers for use in their respective engines. The type and grade of oil used by Pennsylvania-Central Airlines is the same as that used in other of the larger air carrier services. The sludge or sediment
