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Aviation History
1967
1967 - 2118.PDF
International, 2 November 1967 715 Munich—Second Report Disputed N IMMEDIATE END to the controversy surrounding the acci- dent to the BEA Ambassador G-ALZU at Munich in 1958 appears no nearer after the publication in translation last week of the report of the reopened West German inquiry. As already anticipated from advance accounts, the report endorses in general the findings of the original investigation— that ice accretion on the wings of the aircraft was the cause of its failure to become airborne. The only concession which the new report makes to the opposing view—that slush on the run- way caused the accident—is in an admission that "slush must be regarded as a further cause." The English translation of the report has been published by the Board of Trade, which has taken the most unusual step of appending to it, in the same document, a memorandum by the Royal Aircraft Establish- ment, Farnborough, which reaches conclusions in direct contra- diction to those of the West German inquiry, and which states that slush on the runway caused the accident. Simultaneously with the publication of this document, Cap- tain James Thain, who was the captain of the crashed aircraft, issued a statement expressing extreme dissatisfaction with the West German inquiry, and called on the British Government to refute its findings. The British Air Line Pilot's Association, which has supported Captain Thain in his continued attempts to have the findings of the first inquiry reversed, also issued a statement last week. This said that it found the second German report "totally unacceptable," and added: "The report is technically unsound, it contains errors of fact, and fails entirely to revoke the mistaken conclusion of the first commission." BALPA says that its views are "identical with those of the technical experts of the Board of Trade and the Royal Aircraft Establishment, in that slush caused the accident and that wing icing played no part. The association will press for the Government to dissociate itself from the report and will continue to support Captain Thain in his efforts to obtain an objective investigation into the facts." "Conflict of Evidence" Speaking in the House of Commons on October 25, the Minister of State, Board of Trade, Mr J. P. W. Mallalieu, said that the RAE experiments at Bedford had shown that "slush drag could have been the principal or even the sole cause of the aircraft's failure to lift off." But he went on to say that whether in fact it was so or not "could not now be established because of the impossibility of resolving, after such a length of time, the conflict of evidence regarding how much siush was present." G-ALZU, it will be recalled, had stopped at Munich (Riem) Airport when en route from Belgrade to Manchester on Feb- ruary 6, 1958. It remained about two hours on the ground, during which time snow fell. After two attempts to take off, both of which were abandoned because of boost surge in one of the engines, the aircraft returned to the apron; later a third attempt at take-off was made. On this occasion the Ambassador failed to become airborne, and overshot the end of the 1,908m runway; it struck a house and a hut and caught fire. Of the 44 occupants, 21 were killed in the crash and two died later in hospital. Captain Thain, commanding the aircraft, was in the right-hand seat, and the first officer (Captain G. Rayment), who was one of those fatally injured, was in the left-hand seat. Captain Thain said later in evidence that during the take-off run the Vi speed of 117kt was reached, but that at this point the airspeed indicator needle "hovered" and then dropped four to five knots, later falling to 105kt. The calculated V2 speed was U9kt. In March 1960 the West German Commission of Inquiry turned down requests for a reopening of the inquiry, saying that it appeared out of the question that any quantities of water or melted snow "worth mentioning" should have collected. Further- more, it was evident (from eye-witness reports and marks of the emergency tail-wheel in the snow) that the necessary angle of attack for unsticking with clean wings had been attained for a sufficient period before 1,800m of runway had been covered (on the evidence of the captain and others, Vi had been attained at between 1,400 and 1,600m). In July 1964 the UK Ministry of Aviation sent to the West German Federal Minister of Transport some material on experi- ments made with an Ambassador since the accident, to deter- mine the effect of slush on take-off performance. The German authorities, after examining this, decided in November 1964 to reopen the accident inquiry. The concluding summary of the report on the reopened inquiry says that it has not proved possible to clarify com- pletely how the various causal factors combined to bring about the accident. "The wing ice that was present," it says, "is still to be regarded as the essential cause of the accident. [It] did not, it is true, have an unduly great influence on acceleration, but it did reduce lift substantially, and bring about an increase in the required unstick speed. Slush, however, must be regarded as a further cause, since it resulted in a reduction in perfor- mance during acceleration, and may also have caused changes in trim, which, in combination with other secondary effects, had an unfavourable effect on the unstick process." The com- mand situation, says the report, was not entirely clear-cut, and may also have had an unfavourable effect on the take-off process. In the conditions existing at the time, the commission considers, the aircraft would have been able, without any ice on its upper-wing surface, to attain unstick speed and "would have been bound" to become airborne. Take-off Sequence "The present commission," says the report, "was no more able to gain an entirely clear picture of the course of the fatal take-off attempt than was the commission which conducted the initial inquiry. It was clear from eye-witness reports that the nosewheel had been raised half-way along the runway, lowered again after some 60-100 metres, and then, within the last third of the runway, raised again, high enough for the emergency tail wheel to touch the runway." The commission was convinced that the drop in speed, reported by Captain Thain, had occurred in the final third of the runway; otherwise "it is quite incon- ceivable that the take-off should have been continued in spite of the loss of speed." The commission believed that the speed of 105kt, reported by Captain Thain, occurred during the "obviously forceful attempt to unstick at the end of the run- way," or at the moment when the first pilot applied the brakes ("the commission is in no doubt that the brakes were applied"). Captain Thain's assertion that no attempt to unstick was made during the entire take-off was "incomprehensible" and opposed to all practical experience and procedure. On the subject of the rough layer of ice which, it was found by the first inquiry, formed on the upper surface of the wings during the stop as a result of snowfall, the second inquiry con- sidered the report of an eye-witness, made in 1963, to the effect that the wings were free of snow when the aircraft left the apron for its third take-off attempt. In view of the fact that five years had elapsed when the statement was made, while evidence to the contrary had been given immediately after the event, the inquiry rejected it, and concluded that ice was present before the take-off run began, in a rough layer about 5mm thick. The commission "arrived with adequate certainty" at the conclusion that at least 45 per cent of the wing upper surface was covered. Mr R. Szukiewicz, assistant chief aerodynamicist of Hawker Siddeley, reported to the commission that icing produced not more than a negligible effect on the Ambassador's take-off per- formance. He described tests carried out in the winter of 1951-52. But the commission took the view that these tests were
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