Page:CAB Accident Report, Pennsylvania Central Airlines Flight 19.pdf/78

 degree of darkness in the cockpit and outside the plane. Some persons have reported that the blinding effect of a lightning flash in their vicinity has lasted for a good many minutes or even hours with a recurring after image and other forms of interference with normal eyesight which have been noticeable for several days after.

It is evident that the cloud toward which the airplane was flying was very dark and that the airplane was quite close to it at the time of the lightning flash. If the pilots had been looking forward through the windshield at the time the flash occurred in front of the plane, the result could have been so severe as to produce virtual blindness throughout the dive of the airplane to the point of impact.

It is obvious that the sudden blinding of a pilot might seriously interfere with his efficient control of an airplane in flight. While the blinding of the pilots in the present case might have been an added and grave complication in attempting to regain control once the dive had started, it is not believed likely that the optical effect of lightning of itself represents a basic cause for the airplane to change its normal flight attitude and dive toward the ground.

The or pressure wave effect of lightning was described at some length by one of the expert witnesses, Dr. Karl B. McEachron, an electrical engineer of the General Electric Company, who has been in charge of lightning research for the past several years and is generally recognized as an authority of great eminence on the subject. In one type of lightning stroke, there is a relatively long time, slow discharge of small value current which produces a burning or thermal effect. However, there is a very different