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operating in the clear at the time of the accident, well removed from the closest Slgnlflcant convective act1v1ty; and the necessary meteorological parameters for the formation of clear air turbulence were not present (i.e., vertical or hori- sental wind shear, strong Jet stream, sharp upper trough). The subject of pilot and flight engineer competence cannot be conSidered a factor, for all three were well qualified and experienced airmen deSpite havmg less than 100 hours in Electras. Also, the pOSSibility of crew incapacitaticn, even in small degree, by any toxicity is without foundation and is not even suspected. The aircraft itself was virtually new and had not needed appreciable maintenance work; that which had been accomplished had been Signed off in accordance with established practices. ColliSion or threatened collision with another aircraft or object has been ruled out and the flight was being navigated properly.
Eyewitnesses are often in error, particularly in their attempts to recount time lapses, the exact sequence of events, or altitudes. It is difficult, even to a trained observer, to recall accurately the order of an unanticipated rapid succeSSion of events. There is in this accident, however, one condition which fixes the sequence and establishes to some extent a tune boundary between two important elements of observation: (1) the sound, variously described as Itjet noise,“ "low flying aircraft," "unsynchronized motor," and (2) the observation as “a large orange ball of fire." Six witnesses were indoors when startled by a noise of sufficient intensity to get them to look or go outSide.
Certainly, some of their observations cannot be reconciled such as the white light seen by one witness, nor do the various times between events check out with any high degree of accuracy. However, all of the witnesses who were indoors first heard a noise which was followed by a ball of fire.
Several witnesses gave reasonably good descriptimis of obgects Silhouetted between them and the ball of fire. This information correlated well to le the geographic peeition and an apprOXimate altitude band for the fireball. When plotted, the altitudes of Sighting varied from 17,000 feet to about 24,000 feet. while the variation here is wide, it does indicate that the fireball was at high altitude and probably no lower than the 15,000 feet reported on the radio by the crew.
USing a speed of sound of 1,088 feet per second, which is the standard—day average between sea level and 15,000 feet, it can be shown that from a Simultaneous noise and light at 15,000 feet, an observer directly below would hear the sound about 14 seconds after seeing the light. An observer three miles away would not hear the sound for an additional SlX seconds. (Normal temperature variations and even strong winds will make only negligible differences in time ) The loud con— tinuing noise, then, had to occur 14 or more seconds prior to the appearance of the fireball, plus the time interVal between the witness observations of neise and light.
AnalySis of the witness statements shows that the information provided by a majority of the witnesses is reasonably conSistent. The average tune from.noise (at the source) to the appearance of the ball of fire was in the order of 33 seconds, with the largest variation from the average being about eight seconds.
The witnesses who saw the fireball from inception agree that there was no pro» longed fire, but rather a small one which grew quickly into a large orange of red ball and then disappeared in a few seconds. Several witnesses observed that just
