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Aviation History
1954
1954 - 0339.PDF
5 February 1954 163 the Comet 2 a better take-off and landing performance despite the increase of all-up weight—from 107,000 to 120,000 lb. The manufacturers state that the de velopment of the Avon has been more rapid than was expected. Those installed in the Comet 2 are approved by the A.R.B. with a nominal test-bed thrust of 7,150 lb, and Rolls-Royce believe that a period of 1,000 hr between overhauls will soon be achieved in airline service—a figure which compares well with those quoted for modern com pound piston engines. As originally offered for the Comet the Avon had a sea level static rating of 6,500 lb, and an increase to 7,000 lb was not then expected before the completion of a year of civil operation. Capacity payload of the Comet 2 is 13,450 lb, which is equiva lent to 44 passengers with baggage and some 3,500 lb of freight. Assuming realistic fuel reserves and making allowance for head winds not exceeded on 85 per cent of days in the year, the following routes are typical of those on which the aircraft can operate with a full load. The airport temperatures assumed are the average of the daily maxima in the hottest season. It will be seen that in each case there is a useful margin between the estimated take-off weight and the permitted a.u.w. COMET 2 TAKE-OFF: Under representative atmospheric conditions, the Comet 2 can operate from a 6,880ft take-off surface and meet full engine-out performance requirements. The normal four-engined take-off and the three- engined take-off are compared in this diagram. 4 ENGINES OPERATING CRITICAL P0"» UNSTICK POINT 3 EN6INE5(U?^ UNSTICK POINT ,INES(V2) VWW^^W,v»,v\VA^^^^^ 200A (OOm ^SOTS • ' I '' ' 1,000 2DOO 3,000 4pOO DISTANCE FROM START OF RUN 5pOO (feet) F-STOPWAYINOT NECESSARILY PAVED)** T 6,000 7000 Caracas-New York Entebbe-Cairo ... Perth-Djakarta Karachi-Beirut Entebbe-Johannesburg Stage distance (st. miles) 2,116 2,080 1,876 1,992 1,846 85% Head wind (m.p.h.) 47 14 24 97 22 Take-off weight required (lb) 115,500 113,900 110,900 117,000 109,400 Max. permis. take-off weight (lb) 120,000 120,000 116.000 120,000 120,000 Journey time (hr min) 5 19 5 01 4 40 5 25 4 34 Three more route studies show a payload limited by runway length, but here it is emphasized that the conditions shown represent a severe combination of headwinds, take-off tempera tures and high load-factors—which, in practice, would rarely be met. Peak temperatures, for example, are often avoided. Kingston-Montreal Paris-Dakar Barbados-New York ... Stage distance (st. miles) 1,915 2,610 2,100 85% Head wind (m.p.h.) 14 24 36 Payload (lb) 10,300 12,300 11,500 Max. permis. take-off weight (lb) 103,000 118,500 111,600 Journey time (hr min) 4 37 6 30 5 14 Strong prevalent winds, or sector distances at the extreme end of the working range, can also affect payload. But although there is an 85 per cent frequency headwind of 64 m.p.h. on the 2,414- mile route between San Francisco and Honolulu, de Havilland quote a payload of 10,970 lb. Between Lima and Mexico City (2,650 miles, 20 m.p.h. headwind) payload is restricted to 7,200 lb. The makers also put forward a strong case for the Comet 2 on FAMILIARIZATION: Four executives of Air-India International study the Comet training mock-up at Hatfield: (left to right) Mr. E. M. Landford, the company's representative at L.A.P.; Mr. A. C. Gaidar, operations manager; Mr. C. Vishuanath, assistant operations manager; and Mr. R. Oza, chief flight engineer. The airline has ordered two Comet 3s. shorter hauls where a need arises for a high-speed luxury service. Between New York and Miami, for example, the journey times would be 2|-3 hr—compared with existing schedules of 4 hr. Without graphs or tables it is not possible to express fully the take-off performance of a modern commercial aircraft. The take off distance to a height of 50ft (with one engine failing at the critical point) is subject to the influence of variations in take-off weight, temperature, runway gradient and surface wind. How ever, an indication of the Comet 2's take-off performance under "representative conditions" is given by the diagram reproduced above. In this case the take-off distance available is 6,880ft, and the Comet is seen to clear 50ft after failure of the critical engine at the critical speed at its full take-off weight of 120,000 lb. Paved runway comprises only 80 per cent of the available distance; the rest of the take-off is made over the stopway, a surface sufficiently strong to accommodate the aircraft in the event of an abandoned take-off. In normal circumstances the aircraft does not make use of the full take-off distance, which, in accordance with performance requirements, is calculated on the basis that the critical engine will fail. With all four Avons operating the Comet unsticks in 66 per cent of the distance available and, as shown in the diagram, clears the hypothetical 50ft screen in 85 per cent of the distance. Further details of take-off performance, in terms of different combinations of altitude, temperature, weight and distance avail able, are quoted below:— Altitude Sea level Sea level 3,000ft 5,000ft Temp, (deg C) 15 45 25 20 Take-off weight (lb) 120,000 120,000 119,000 114,500 Take-off distance (ft) 6.340 8,250 8,460 8,600 These figures should help to dispel the tendency to associate jet airliners as such with abnormal runway requirements. In fact, the Comet 2 has a better take-off performance than the Series 1, and both types are comparable in this respect with conventional piston engined airliners in the same all-up-weight categories. Moreover, de Havilland state that under the 1951 B.C.A.R.s [which are accepted as the most advanced performance code yet enforced] the Comet 2's climb requirements are never likely to restrict the maximum permissible take-off weight to a level below that determined by aerodrome length. Because of its exceptional rate of climb on three engines at 120,000 lb, the Comet 2 meets the regulation (second segment) take-off climb requirement up to 9,700ft and a temperature of 25 deg C. With its high block speed, and incorporating the lessons of nearly two years of passenger service with Series Is, the Comet 2 emerges as an economically attractive airliner in its own right. Its manufacturers affirm that the Series 2 and the Series 3 (the prototype of which will fly this year) must be regarded as stable companions rather than as rivals. The Comet 2 is available for reasonably quick delivery, and there are good prospects for orders additional to those already placed by operators in Britain, Brazil, Japan, Argentine, France and Canada. FLIGHT SAFETY FOUNDATION FROM a correspondent in New York we have received a summary of the 1953 activities of the Flight Safety Foundation. This shows that the Foundation's Accident Prevention Bulletin, of which there were 28 separate issues last year, now has a circula tion of over 6,000. Pilots' Safety Exchange Bulletins were distributed on a similar scale, bringing the total number of these two publications to over 200,000. Other bulletins were published for mechanics (over 15,000 copies of each issue were requested by industry) and for private and agricultural pilots. The F.S.F. also launched Howard Kurtz's invaluable study of passenger psychology The Common Man Up In The Air, of which at least 45,000 copies have been distributed (the total quantity is unknown because I.A.T.A. and A.L.P.A. have permission to reprint and distribute it). Two other publications giving useful advice were
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