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content which might be collected in an airplane engine would depend largely upon the usage of the engine, particularly the amount of power applied over extended periods. In other words, if the engine is operated at a high rate of horse power over an extended period of time, more sludge or sediment can be expected than if the engine is operated under lesser horse power conditions. If the cuno type filter which was installed in aircraft NC 21789 was free of sediment to an extent which would permit a normal oil pressure of 60 lbs. at the time of departure, it is not likely that sediment could collect in an amount that would be alarming prior to reaching the next scheduled stop. However, should the filter clog up with sludge or sediment so as to reduce the oil pressure below 40 lbs., the oil would be by-passed around the filter so that adequate lubrication would be provided to the engines and no stoppage of oil would result to the lubricating system. Thus, while the filter is not absolutely necessary to the operation of the engine, it contributes to its economical operation.
It is quite likely that if a material loss in oil pressure was indicated shortly after taking off, Captain Scroggins would have returned to the Washington-Hoover Airport. When this fact is considered with the evidence to the effect that the condition of both right and left engines after the accident was almost identical, the conclusion seems clear that the condition of the oil filter prior to departure from Washington could not have had any bearing upon the cause of the accident.
No reason has been found to suspect an engine failure while in flight. Not only does the direct physical evidence give no suggestion of such a failure, but the circumstances of the accident were such that engine failure partial or complete, could hardly have initiated it. Had Captain Scroggins
