Page:CAB Accident Report, Pennsylvania Central Airlines Flight 19.pdf/75

 of lightning flashes over any considerable period of time, there was at least one flash and possibly two flashes a very short time before the crash of the airplane and one of the results was the well-established splintering of the wooden butt of a rifle which was in Mr. Baker's barn some distance from the scene of the accident.

A flash of lightning close to an airplane in flight, and less than thirty seconds later, the crash of the same airplane into the ground, are two events of so much importance taken together that they cannot be dismissed as a mere coincidence and their relationship must be analyzed to the fullest possible extent.

The experts who testified and the data collected reveal the extent of the knowledge thus far accumulated concerning the causes, character, and the various results of lightning discharges, together with their effects on aircraft in flight and their crews. As relating to the accident under investigation, our analysis appropriately may be divided into four general effects of lightning;–thermal, electrical, optical, and mechanical.

The or heat effect of lightning is the one typically found on the many aircraft which have been struck in flight. Generally, lightning enters and leaves airplanes at two different and often widely separated structural extremities, such as the nose, the tips of the wings, the units of the tail assembly, propeller blades, radio antenna masts, pitot tubes, etc. The point where the lightning enters or leaves the plane usually can be discovered by a hole or indentation "as small as a pin prick" or "as large as two silver dollars." Occasionally, the external fabric of an airplane may be burnt at the point of entrance or exit of the lightning. Experience has revealed that the speed of the airplane through the air quickly extinguishes these fires leaving indications of burns in straight lines rather than in curves.