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Aviation History
1958
1958 - 0409.PDF
28 March 1958 425 completely encased in titanium, and all fire detectors are of the Graviner Firewire type. Rolls-Royce have made other important contributions to the Comet 4, in particular to the suppression of its noise (by an amount sufficient to have already satisfied the Port of New York Authority), and to the reversal of thrust for landing. The latter installation is not yet sufficiently developed for inclusion, as was at one time hoped, in the first of B.O.A.C.'s 19 Comet 4s, but it will be fitted retrospectively to those aircraft. The prototype Comet 2X has undergone ground tests with a prototvpe reverser, and the proto- type Comet 3 is at present being equipped with reversers (on the two outer engines) for actual landing tests which will be made during the coming summer. Finally—and most important from the point of view of selling the Comet to the passenger—the interior has been completely restyled for B.O.A.C. In accord with modern interior-styling practice the Comet 4's cabin represents a complete breakaway from the Corporation's traditional, and rather dull, dark blues and greys. Much use is made of colour, with a result which—judging by the impression which the mock-up gives—will more than match the "jet-age decor" which B.O.A.C.'s American airline rivals are introducing. The actual seating layout is of course flexible, the structural bulkhead in line with the wing spars forming a natural division for the different classes. B.O.A.C. have numerous schemes in mind: they will probably begin their Comet services to Sydney with 16 passengers forward in 56in pitch de luxe, four-abreast seats, and 43 passengers aft in 40in tourist, five-abreast seats. Any number of permutations of seating layout for the various classes of passenger can be played by B.O.A.C. (maximum "economy," or T-34, seating, if installed throughout both cabins, would be 81). D.H. have achieved the utmost possible flexibility of cabin layouts by providing lavatories and pantries both forward and aft in the cabin. An accommodation diagram appears on p. 423. Five years will have passed between last deliveries of the old Comet 1 and first deliveries of the new Comet 4. Those years may have seemed long to the many who have wished impatiently to see the Comet re-established in service and ordered by overseas air- lines. But the time has been well spent, to a degree which tempts one to say that if any of the new airliners is likely to give trouble-free service from the word go, that airliner will be the Comet 4. FLIGHT TESTING THE COMET 4 IN a week or two's time the fruition of three years' design anddevelopment work, and of 50,000 hours' flying, will emergefrom the de Havilland factory at Hatfield in the shape of the first production Comet 4 for B.OA.C, G-APDA. Normally, production aeroplanes issuing from the de Havilland assembly lines are not the concern of experimental flight-test, whose responsibility for developing the prototype is usually dis- charged by the time the first production aeroplanes appear. The first production Comet 4, however, is sufficiently different from its progenitors as to require an "experimental" flight-test pro- gramme rather more elaborate than a normal production test. This programme will not be as lengthy as it might have been without the existence of the Comet 3 prototype, now 3i years old and with 830 hours (in 581 flights) to its credit. Had the Comet 3 never been built, D.H. would have been confronted with perhaps a two- year programme of Comet 4 flying. As it is, they hope to have it ready for delivery to B.O.A.C. within 18 weeks of its first flight, in September of this year. About 250 hours of Comet 4 test-flying should qualify the aero- plane for its full certificate of airworthiness. The distribution of these hours into various kinds of flight test work will be outlined in a moment: first must be recorded the indispensable contribution made by the Comet 3. The prototype Comet 3 made its first flight at Hatfield in July, 1954, during the dark days of the Comet 1 investigation. Its future as a production aeroplane was uncertain for a year and a half, until in February 1955 B.O.A.C. placed their revitalizing order for an improved Comet, to be designated Comet 4. This New Comet, of which B.O.A.C. ordered 19, was to be the embodiment of all the experience and knowledge acquired, at such cost, to that date. D.H. reckoned that it would take three years to complete the transformation of their jet airliner, a measure of the amount of design and production work that lay ahead (see previous article). This estimate, though de Havilland have worked hard to reduce it, has in the event proved just about right. Throughout this period, the responsibility of the experimental flight-test organization has been the testing and evaluation of the Comet 3 prototype in terms of the new Comet 4. Undoubtedly the greatest single advantage of the Comet 3 has been its aerodynamic Of the 50,000 hr of Comet flying to date, some 5J0OO hr hare been in the course of makers? test flights. Members of the test team seen here (reading down) are E. Brackstone Brown, engineer; A. J. Fairbrother, aerodynamics; J. A. Marshall, instruments. identity with the 4. This has permitted D.H. to satisfy themselves in advance about the performance, stability and handling charac- teristics of the new Comet 4. Though aerodynamically identical, the Comet 3 was unrepre- sentative in some fundamental respects—in particular, in its power, structure and weight—and it was untypical in many lesser respects also, e.g., in its systems and equipment. About a year ago, when Comet 4 redesign-work was well advanced, it was decided tem- porarily to withdraw the Comet 3 from flight tests and to make it as fully representative_ of the 4 as it could reasonably be made. This work, which began in July 1956, took seven-and-a-half months to complete. This reworked Comet 3 was dubbed the "3$." Actu- ally, except for its structure (which could not have been much The three de Havilland pilots primarily concerned with the Comet flight test programme are (left to right) Peter Wilson, John Cunningham (D.H. chief test pilot), and Peter Bugge. changed without building a new aeroplane) it was almost a Comet 3|. The biggest change was to the engines: the Rolls- Royce Avon RA.26s of the original Comet 3 were replaced by the RA.29s of the 4, a modification which involved radical alterations to the engine-bays. Numerous other modifications were incorpor- ated, mainly to the systems, in order to evaluate in advance new detail-design features of the Comet 4. (The flying controls system had already been amended to incorporate q-feel.) This work made it possible to reduce the tests required of the first Comet 4 to the absolute minimum, and modifications to the Comet 3 will have saved D.H. possibly as much as a year on the whole Comet 4 programme. Because the structure could not be much altered, there were certain operating limitations on the modified Comet 3. For example, it was designed for a maximum weight of 145,000 lb, whereas the
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