Page:CAB Accident Report, Pennsylvania Central Airlines Flight 19.pdf/80

 approved to withstand any reasonable impact or pressure load, it appears entirely possible that a lightning flash near the nose of the plane might result in their being smashed in. The plane must have entered a torrential downpour of rain at the time of, or immediately following, the flash of lightning in its vicinity, and if the cockpit windows had been smashed in, the pilots might have been subjected not only to the violent impact of flying pieces of glass but also to a withering stream of water striking them with all the force of the airplane's speed through the air of 150 miles an hour and upwards. The smashing of the cockpit windows as a result of an unusually powerful lightning discharge near the nose of the plane with a consequent serious interference with the pilot's control of the airplane remains a possibility.

No airplane has been reported to have suffered structural damage resulting from the mechanical effect of lightning while in flight. Furthermore, Dr. McEachron testified that the available data indicate that the destructive force of lightning decreases in proportion to the altitude above the ground and, as already mentioned, it appears that the airplane in the present case was flying at an altitude of 6,000 feet at the time of the lightning flash. However, as Dr. McEachron said during his testimony, "We are looking here for the unusual thing, not the ordinary thing," and the rare chance of serious damage to the airplane or its controls caused by lightning should not be overlooked. If the mechanical effect of lightning may have been a factor causing the accident, the smashing impact with some part of the plane's structure typically would have left none of the usual indications of a lightning strike of a thermal nature. A violent pressure wave conceivably could damage the tail of an airplane to such an extent as to cause the loss of all normal