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Aviation History
1959
1959 - 0952.PDF
April 1959 477 A MATTER OF PRINCIPLE ib VER since the result was made known of the inquiry into the»-/ take-off accident to the C.P.A.L. Comet 1A at Karachi on March 3, 1953, I.F.A.L.P.A. have been attempting to show thatthe verdict that there was an error by the pilot, Capt. C. H. Pentland (who was killed in the crash) was not a just one. With equaltenacity, they have championed the cause of Capt. R. E. H. Foote, pilot of a B.O.A.C. Comet 1 which crashed when taking-off fromRome in 1952 in what were claimed to be broadly similar circumstances. The Association have sought to show that, on "the Comet 1,the margin between the unstick speed and the stalling speed was unreasonably small; not only because a pilot might make an errorof one or two knots in following the unstick technique laid down in the manual, but because a margin in speed is necessary to coverthe increase in stalling speed which must occur as the attitude of the aircraft is changed. At the weight at which the Comet 1Atook-off at Karachi this was 51 kt between the ground stalling speed and the unstick manual speed, and a further 3| kt which wasgained while the aircraft was rotated to its unstick attitude. The pilots have been unbending in their attitude to the verdictsof the two accidents, and since the results of subsequent manu- facturers' tests were made known have been pressing for newinquiries to be opened by the Pakistan, the Italian or the Canadian authorities, or by the M.T.C.A. All their efforts were unsuccess-ful and at one time they threatened to go on world-wide strike every March 3 until the Pakistan findings were reviewed. With publication of a recent joint statement by I.F.A.L.P.A.and de Havilland relating to the accident at Karachi it seems that the pilots can at last feel that honour has been satisfied. While de Havilland maintain that they have "throughout beensatisfied that the techniques which they taught satisfactorily avoided any difficulties inherent in the somewhat narrow marginof speeds," and point out that no practicable increase in unstick speed would have safeguarded the aeroplane against consequencesof departure from the proper technique, the pilots have obtained the manufacturer's recognition that "the aeroplane had a smallermargin for departures from its prescribed technique than con- temporary piston-engined aircraft."The prescribed technique was to raise the nosewheel at 80-85 kt I.A.S. and then return it lightly to the ground until the unstickspeed was reached. At this speed, the Comet was to be lifted off by a firm, controlled movement of the control column until immedi-ately after leaving the ground, when the column was to be moved forward again to check the vertical movement away from theground and any tendency to pitch up; after which climb was to be initiated by a gentle backward movement of the control at4 kt above unstick speed. If this technique was not* followed, poor acceleration resulted from the unnecessarily nose-highattitude. Following the accident, a series of extensive special tests weremade. These showed that the stalling speed near the ground was higher than the corresponding free-air figure, and that this dis-parity increased with gross weight. A "wider margin for error" was obtained by modifying the leading edges of Comets and, asis widely known, is incorporated in the lAs and 2s now in service. The Comet 4 cannot be stalled at any weight during the take-offrun, even if the tail bumper is pulled on to the ground. Although no reference is made to the Rome accident in thejoint D.H./I.F.A.L.P.A. statement, the implication is sufficiently clear for the Karachi and Rome incidents to be linked in currentnewspaper comment on the statement. Everyone must be relieved that at last the dispute is over, though the only really positiveresult is the proposal of new take-oft requirements. These stipu- late that the elevator control movement to initiate unstick shallnot be made at a speed lower than 1.1 times the minimum speed at which the aeroplane can be made to lift off the ground andcontinue the take-off without displaying any hazardous charac- teristics. (An exception occurs in the case of aeroplanes withminimum speed limited by landing gear geometry or elevator effectiveness, when the factor may be reduced to 1.05.) SOUTH AMERICAN JET *lljROM Buenos Aires, from the camera of George Errington of-* de Havilland, come the lower three pictures of the arrival there last month of the first Aerolineas Argentinas' Comet 4. From leftto right below are Peter Wilson, the D.H. pilot seconded to A.A.; D.H. technical representatives R. W. Sands and P. A. Hatswell;and J. Bridger of Waldron Aviation, D.H.'s local distributors. At bottom are (left) the welcoming crowd as seen by the dis-embarking passengers; and the general scene at Ezeiza airport, B.A., after the arrival. Note the Latecoere 26—probably the onlysurviving specimen of this French postal monoplane (450 h.p. Renault)—which was on show to provide a link with the earlydays of Argentine air services. On the right is the first published •air-to-air picture of the first Aerolineas Argentinas D.H. Comet 4. V- ••« ,<. - *^4
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