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Aviation History
1956
1956 - 1060.PDF
206 FLIGHT Seen about to take off from Bristol for B.E.A.'s headquarters at Ruislip in a Sycamore are Mr. C. T. D. Hosegood, Bristol chief helicopter test pilot (at the controls); Capt. G. W. James, B.E.A. flight operations director; and, in the rear seats, Mr. H. E. Marking, B.E.A. secretary, and Mr. R. Whitby, performance and analysis manager. They had been attending to Bristol 173 business (see p. 170, "Flight," last week). CIVIL AVIATION . . . THE SEPARATION PROBLEM " TPHE ability of air traffic control to regulate expanding traffic--•- flows must largely depend upon the accuracy with which the regulation can be made; for whatever steps can be taken to improvethe radius of control, it is certain that traffic densities will increase. Solutions to the problems of vertical separation are consequentlyof first importance, for present height maintenance inaccuracies make nominal l,000ft-separations inadequate for safety on con-sideration of altitude alone, and too much reliance must be placed on "fortuitous horizontal scatter"—two aircraft at the same heightbut not at the same place at the same time. Even this element of chance is decreasing with improved directional aids such as V.O.R. The inaccuracies of aircraft altimeters—the fly in the separationointment—have been studied by a special I.C.A.O. panel, and recommendations are to be put into effect as soon as possible.The panel's analysis listed 15 contributory factors to account for pilots flying at incorrect altitude, six of which were consideredto be of major importance. Errors in the instrument calibrations due to the diaphragms, hysteresis, friction and instability, mayaccount for discrepancies of 170ft at 10,000ft and 300ft at 20,000ft, and could be reduced by rejection of altimeters which cannot meetcertain mechanical tolerances now proposed internationally by the I.C.A.O. panel. In addition, new electrical servo instrumentswhich are being developed should be accurate to a quarter of one per cent of scale-reading, or half of one per cent if the electricalsystem fails. Position error of the static pressure source is responsible foreven greater difficulties. The growing speed of modern aircraft may result in pressure variations between aircraft of the same typechanging from one year to the next. The solution proposed in this case is the preparation of static pressure-system correction cardsfor application by crew members, and although this will be incon- venient, at least the static pressure-system errors have been estab-lished for most present-day aircraft. Even assuming completely accurate altimeters, vertical separa-tion is influenced by the pilots being unable to maintain a com- pletely consistent level, although this error can be reduced by the useof auto-pilots with locking height control. "Flight technical error" —the term given to these pilot inconsistencies—has been shownto increase with altitude within the range of 175ft at 10,000ft alti- tude to 440ft at 20,000ft, and consideration must be given to thecase where an additional 500ft, say, has to be climbed to achieve the correct nose-down angle of attack for an assigned level. Someallowance for abnormal weather conditions must also be made. Combined errors under all these conditions indicate that thelikely separation on three in 1,000 occasions (where normal separa- tion is 1,000ft) will vary from + 87ft at 10,000ft when flying atthe standard altimeter setting of 1,013.2 mb to —786ft at 20,000ft near QNH boundaries when flying on regional altimeter settings. The panel consequently recommended that a standard pre-take-off check be made, static pressure correction curves be applied, procedures where QNH is used be improved, and positive controlbe exercised over aircraft at QNH boundaries when extreme pressure gradients exist. Accurate QNH values and auto-pilotheight lock should also reduce the flown altitude scatter. Civil aviation authorities, operators and pilots all have respon-sibilities in vertical separation safety. The longer term solution. appears to rest with the manufacturers—and here prospects areencouraging. . . BREVITIES A FURTHER proving flight (see Flight, July 20) has been•**• made by the Tu-104, from Moscow to Irkutsk in South Russia. The 2,790-mile flight was made in slightly less than sixhours. Next year it is planned to fly from Moscow to Vladi- vostok, a greater distance than Moscow-New York. * * * Air-India is planning to run a weekly service between Londonand Sydney by way of Madras before the end of this year. * * * Captain Peter Fair has been appointed general manager ofBahamas Airways. * * * The American University, Washington, will conduct the TenthAir Transportation Institute from October 16 to November 2. * * * Union of Burma Airways representatives have been in Dublinstudying Aer Lingus Viscount operations. * * * B.W.I.A. announce fare reductions between Barbados and SanJuan and other points in the N.E. Caribbean, following the agree- ments at the Cannes I.A.T.A. Conference.* * * There was a 34 per cent increase in business transactionsthrough the I.A.T.A. clearing house during the first quarter of * * * The House of Representatives has passed a bill banning thesupply of alcohol to passengers on flights made in the U.S. The ban does not apply to international flights. * * * Five more Convair Metropolitans are to be added to the S.A S order for 11 at a total cost, including spares, of approximately £1,730,000. Delivery will begin in January 1957. A Transair "Dakmaster" was used recently for an exchangeof students between Moscow and London in association with Aeroflot. The change-over point for 25 English and 25 Russianstudents was Prague. * * * Air Charter expect to operate 500 flights—carrying over athousand cars and motor cycles and 3,500 passengers—between Southend and Calais and Ostend during the five day period at theend of July. * * * Aer Lingus made a net surplus of £41,495 during the financial year 1955-56 after development expenses, balance of capital loss and a sum for taxation provision had been written off the operating surplus. The overall revenue load factor was 67 per cent. Now called the Super "Star" Constellation, here is the first L.I649A taking shape at Lockheed, Burbank. Five airlines have now ordered 46.
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