Much of the investigation hinged on tests and analysis of the body and clothing worn by the man who jumped from the aircraft about 1.5 miles prior to the crash.
The nature of the crash, and the subsequent fire, destroyed much evidence and hindered the investigation. What little material that had fallen from the plane and the body and clothing of the man comprised much of the evidence that was to prove that the cabin is where the fire took place, rather than in the cargo hold or electrics bay as had been thought at first.
Initially, United Airlines did not believe that anyone had jumped from the plane. They felt that cabin pressure would have not allowed this. At that time it was not established that the cabin had been depressurized in order to remove smoke and heat.
Searchers, among them the local National Guard unit, combed the area in search of a “black object” that witnesses had seen fall from the passing aircraft. Azimuths were taken from the positions of two men, who had stood at two different locations, approximately two miles from the crash site, and had claimed to have seen something fall from the airplane. The area where the azimuths intersected is where much of the search was conducted. The body was found after someone noticed wilted leaves on broken tree branches. This is the spot where the free fall victim was found.
It should be mentioned that the passenger who jumped from the left side of the plane did not strike the tail of the aircraft and that he was followed by a dense cloud of smoke.
The Civil Aeronautics Board Aircraft Accident Report Page 11 states that the free fall victim exited the aircraft through an emergency window over the left wing. A British Aircraft Corporation Memorandum states that it was the “No. 4 window”.
In a B.A.C Incident Report there is mention that a preliminary check indicated that no nitrates were found in any of the burns suffered by the free fall victim. For example: no explosive residue was found. Also there was no smoke found in his lungs. The C.A.B report, Page 11 states that the free fall man, “ received burns on the hands, face, and neck before death but had only a few carbon particles in his trachea and a carbon monoxide level of 5% in his blood.' (According to the report, a concentration of less than 10% carbon monoxide is considered negative). “The upper portions of his clothes were impregnated with soot.”
The British Aircraft Corporation, with the concurrence of the Civil Aeronautics Board, conducted tests on “samples of aircraft structure, components, and the free fall victim's clothing.” Dr. Robert Graham Ph.D., B.Sc., A.R.T.C., F.I.M presided over the experiments and wrote the final report dated October 19, 1964.
Perhaps the most intriguing of Dr. Graham's experiments were those performed on the clothing belonging to the free fall victim. (Other tests performed on various parts of aircraft furnishings will be discussed as time allows).
Dr. Graham was aware of the complicated task that was made more difficult because of the destructive nature of the crash and the ensuing fire on the ground. In the beginning of his report he states, “It was considered important…that all evidence which could be reasonably disassociated from the effects of the fire subsequent to the crash should be exhaustively examined for indications of the prime cause of the fire.”
Specimen #1 and #2 were small pieces of cloth, approximately 4” X 6“, that were taken from the free fall victims suit jacket. One piece was from the front of the jacket, while the other was taken from the back of the jacket. The lining and the cloth inside the jacket were attached to the back of the jacket. The back of the jacket “had the appearance of being scorched.”
“The materials received were first examined for fluorescence or variations in fluorescence in ultra-violet light. Thicker sections were then x-rayed at three levels of penetrating power, to locate any features of interest. This was followed by visual and microscopic examination. Thereafter deposits were removed and examined by infra-red and emission spectroscopy. The lining behind the portion of jacket showing scorching was extracted to remove any remaining traces of oils or similar liquids and this extract was examine chromatographic techniques. Deposits were analysed chemically where necessary. Finally, the features found on the scorched jacket…were reproduced in the laboratory.”
”…The examination of Mr. 's suit material provides evidence as to possible initial source of the fire.“
“The suit material from the back of the jacket was thoroughly cleaned in benzene and dried. The lining which had been benzene extracted was then folded in it to simulate the conditions at the front of the jacket. Three drops of 70% ethyl alcohol were dropped on the pad thus formed and the vapour was ignited. The alcohol burned over an area of about 1 inch in diameter with a nearly invisible blue flame. This flame eventually extinguished itself and examination of the area wetted showed that the man made fibre had been heat affected in a very narrow ring at the edges of the flame. The area in the centre of the wetted area was completely unaffected. The appearance of the few threads which had been heat affected showed similar characteristics of filament melting to those of the front heat affected original sample, but to a much reduced extent.”
“A similar sample was wetted with a hydrocarbon fluid with a final boiling point of approximately 250 degrees centigrade equivalent to aviation kerosene. The wetted area in this case was about two inches in diameter. The vapour was ignited and burned with a luminous flame with the production of smoke. The fire was, as in the case of the alcohol, allowed to burn till it extinguished itself. Unlike the alcohol the edge of the flame retreated as combustion proceeded. The original boundaries of the combustion area showed the man made fibre threads to have partially fused. The degree of fusion increased as the flame retreated and eventually the fabric itself completely charred. This charring was not found on the piece of cloth from the front of the suit. It would seem, therefore that the combustion which produced the heat affected area had either a limited time of effect or was limited to a narrow temperature range. The heat effect was uniform over the whole area, Fig 1B, and this area was relatively large. It could not have been caused by 70% alcohol, for the intensity of combustion was insufficient to cause the effect over the whole combustion area. The intensity of the kerosene type flame was sufficient to cause the effect but only at the edges over a short period of time. Thereafter, the intensity would have charred the material beyond the degree found. Another experiment was carried out, therefore, with a more volatile hydrocarbon, a commercial lighter fluid. This fluid burned like kerosene type fuel and, allowed to burn to extinction in a large wetted area charred the last of the area of the burning zone exactly like kerosene. A small splash of lighter fluid, however, burned at such a rate that charring was avoided at the centre of the area. This indicates that the heat affected zone on the front of the suit was caused by fluid which burned, like the small splash, at a relatively uniform rate all over. The inference is then, that the original damage was caused by a fuel whose intensity of combustion was equivalent to that of kerosene, but which evaporated so quickly that there was no build up of temperature across the splash zone. This could possibly have been caused by burning a lighter-type fuel already near its boiling point; alternatively it could have been caused by a fluid which vaporized very quickly at ordinary temperature, such as a splash of a liquid petroleum gas such as butane, or a solvent such as a paint thinner or remover.”
“It has been shown that the condition of the suit material can be duplicated on a small scale in the laboratory. These experiments and analyses of the suit materials suggest that the source of the fire affecting the suit was the ignition of a liquid hydrocarbon or similar liquid of a relatively volatile nature. This liquid apparently spurted or splashed while ignited and thus started the fire. The results seem to indicate that while a liquid petroleum gas could have produced the evidence found, the chromatographic analysis suggest that a liquid such as a petroleum spirit, or similar liquid of a paint thinner, or remover, or even of a kerosene quality, should be sought as the material responsible. This infers that the liquid responsible was one not normally part of the basic aircraft, with the exception of the kerosene. There was, however, no evidence of a fuel leak into the cabin nor of an aircraft fuel fire prior to the crash and the question of aircraft fuel being involved can be discounted. Moreover, there has been no evidence found for the existence of an underfloor fire in flight. It would appear, therefore, that the source of the liquid whose spurting or splashing caused the scorch mark on Mr. 's suit and presumably triggered the cabin fire was a liquid or combustible taken on board the aircraft.”
Robert Graham gave testimony on January 15, 1965 at the Public Hearing that took place in Knoxville, Tennessee.