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Aviation History
1960
1960 - 3096.PDF
1012 FLIGHT, 30 December 1960 Boeing's Trimotor . . . 1,000-1,600 st-mile range and a landing field length of 4,700ft to5,200ft. American domestic fare levels really demand that if four-abreast seats are used for first-class, then six should be usedtourist-class, since at five-abreast tourist-class revenue-rate is seven per cent down on first-class. Between June and September, the Boeing 727 was argued-outwith the airlines. Most were against four engines on the score of operating cost; TWA and United had a case to make for a 136inwide fuselage; others wanted much longer range. A strong case made against a twin-engined layout was the declaration by theFAA that, until it was demonstrated that other rulings could be adopted, twin jets would be subject to minima similar to those oftwin piston-engined aircraft. At Idlewild, for example, these are 300ft and half a mile, compared to 200ft and half a mile for athree- or four-engined aircraft. Translated into annual delays, on just over 11,000 scheduled departures a year, the picture lookslike this:— Departures delayed by one hour or more (per cent) Annual delays of one hour or more (hr) Departures delayed by more than 2hr (per cent) Annual delays of more than 2hr (hr) Two-engine 3.1 342.0 2.0 221.0 Three-engine 1.14 126.00 0.34 38.00 Difference 1.96 216.00 1.66 183.00 It was during the autumn of 1959 that the 727 emerged as athree-engined transport of about its present size and weight, and apart from the choice of powerplant—which still lay betweenRolls-Royce/Allison and Pratt & Whitney—the design was finalized on September 18, 1959. The wing has 32° sweep and less dihedral than the 707, so asto reduce Dutch roll. Simple dual-wheel main landing gear was adopted (the Trident is four-wheel) and the upper body above thechine is standard 707 production, except that the lOin X 14in window (as fitted to some 720s) and big doors—48in X 56in,larger than in any other 707—are standard. Under the project number 727-323 a number of different three-engined layouts were studied, including a V-tail (rejected because of the possibility of fluid running into actuating units), a twin-finarrangement and another with two pods under the wings and a pod on the tail. As Boeing point out, there are just so manyplaces to put a third engine—all in the fuselage. Nor, as a matter of history, is aft mounting new to them, since some experimentalinstallations were made on a B-47 about 15 years ago. So the 727 grew a third engine in the tail, and the tailplane wasraised to a T-position to keep it dear of the wash of the very big, triple-slotted flaps that give the aircraft its field performance, andthe fin was extended to increase the arm and keep the tail light. These changes gave rise to charges that Boeing had copied theTrident, and they are a little sensitive about this. But they are more seriously concerned at being charged with copying theCaravelle, since Sud have a very good patent (2,863,620) pro- tecting just the three-engine arrangement adopted by both Boeingand de Havilland—as well as bifurcated intakes in each side pylon for good measure. Boeing offered two engines: the Rolls/Allison AR 963(RB.163) of 12,7501b thrust and, subsequently, the new Pratt & Whitney JT8D, commercial version of the J-52. This latter enginehas run 13,500hr, completed 325hr flight running and has passed its 150hr production test. Perhaps for this reason, perhaps becausean operator prefers a home to an overseas design, both Eastern and United have chosen the Pratt & Whitney engine although, asa P & W man told Flight in New York: "Rolls-Royce are a very tough competitor." The central engine is suspended from an overhead beam, and isaccessible from underneath or on either side via hinged cowling panels which divide on to the aircraft's lower centre line. The hinge pins can be removed and the complete cowling detachedwhen required. Carried with the aircraft is a special portable hoist, which picks up on two points on the port side of thefuselage just above the engine; this tool can be used to carry out an engine change if proper ground equipment is not available. The same two-door type thrust reverser is used on all threeengines, exhausting horizontally from the central engine and vertically for the two side units. Fan flow is mixed with theturbine efflux in the JT8D so that a common reverser is possible. The actual unit will be a modification of the JT4 suppressor,about 90 per cent common with that in the 707. Cascade vanes will not be used, and it is hoped to achieve a reverse efficiency of50 per cent. At the same time, with good hot/cold flow mixing and compressor sound-absorbing panels in the inlet duct, Boeinghope to reduce noise below present levels. The short-haul nature of the 727 makes its manner of use inlocal service worth considering. While the normal passenger rear ventral entrance is by 33in-wide retractable stairs, like theCaravelle, Eastern have bought for their aircraft a retractable stair for the front steps, which folds up under the normal floor.The middle engine can be kept turning during ultra-short turn- rounds, and in any case vapour-cycle air conditioning and a.c.electric starting are to be used to reduce turn-round time. The starting technique, in which the alternator and Sundstrand driveare used as a synchronous motor and variable-ratio starting gear- box, is most interesting, as it is the first practical example ofa system believed to have been pioneered in Great Britain two years ago. Other aids to rapid turn-round are a single-pointrefuelling system through which fuel can be delivered at 600gal/min; fore-and-aft carry-on baggage racks; a separategalley loading door; and a relatively high landing weight. In all respects, the Boeing 727 offers stern competition to theD.H. Trident. But in the matter of automatic flare-out and automatic landing, even of fully integrated autopilot systems, the727 apparently offers nothing more than its predecessors. The current feeling at Boeing seems to be that autopilots are difficultand complex enough without trying to duplicate or triplicate them to serve additional super-reliant functions (see Flight, Novem-ber 25, page 840) beyond a possible single-channel, "pilot take- over" landing system. Only in one respect has any concession tolater developments along these lines been made; the flying con- trols are now powered and duplicated. But manual reversion hasbeen retained—an engineering expedient unthinkable to most British engineers in this year 1960. * • * The following table is a revision of that published on page 938of Flight for December 16, which it supersedes. The table com- pares the time-scales of the Boeing 727 and the D.H. TridentMk 1, and it shows that, though Boeing committed themselves to their project much later than de Havilland did to the Trident,D.H. concedes nothing to Boeing in the speed with which their programme is being implemented. It is generally agreed that theGovernment's political intervention over BEA's order in 1957 wasted a whole year; on the other hand, approximately one year(February 1958—February 1959) was spent on the design of an aircraft that had to be revised because it had grown too large forBEA's requirements. But, using as the criterion the time taken from start of design to first delivery, it will be seen that the Tridenttime-scale is exactly the same as that of the Boeing 727: — COMPARATIVE TIME-SCALES Initiation of project studies Start of final design First flight... First delivery Start of final design to first flight First flight to delivery ... Start of final design to delivery Boeing 727 Summer 1956 September 1959 October 1962* January 1964 3 years 1 month 1 year 3 months 4 years 4 months D.H. Trident Mk 1 Summer 1956 February 1959 December 1961 June 1963+ 2 years 10 months 1 year 6 months 4 years 4 months* *"Autumn 1962." *"Mid-1963." jSay 3 years 4 months if allowance is mode for political intervention in 1957. FORTHCOMING EVENTS Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. 3. RAeS Astronautics and Guided Flight Section: "Planning of Missiles Acceptance Trials," by J. F. W. Mercer and A. R. Cowthorne. 4. BritIRE (Radar Group): "Automatic Techniques in Civil Airline Communications Systems," by W. E. Brunt. 5. RAeS: Young People's Lecture, "Gyroscope and Pendulum —the Modern Travel Agents," by R. J. Lees. 6-7. RAeS (joint meeting with College of Aeronautics and BIS at Cranfield): Rocket Propulsion Symposium. 9. RAeS Historical Group: "Rebuilding and Flying Historic Aeroplanes," by Air Cdre A. H. Wheeler. BritIRE (South Wales Section): "The Measurement of Ionizing Radiation," by R. G. Wood. BritIRE (West Midlands Section): "An Equipment for Automatically Processing Time-multiplexed Telemetry Data," by N. Purnell and T. T. Walters. 12. RAeS: "The Law and Science in Aeronautics," by H. Caplon. 11. 11. Jan. 12. Institute of Metals: "Metallurgical Research at High Pressures," by Dr J. E. Hilliard. Jan. 13. RAeS Rotorcraft Section: a.g.m. and "Certification of Civil Transport Rotorcraft with Particular Reference to Multi-engines," by H. E. Le Sueur. Jan. 13. Society of Instrument Technology (Midland Section): "Controls Associated with Flying," by Capt A. M. A. Majendie. RAeS Branch Fixtures (to Jan. 6): Jan. 2, Derby, a.g.m. and lecture. Jan. 4, Bristol, "Bird Flight," by J. L. Naylor; Brough, "Problems of Rocket Engine Development," by A. V. Cleaver; Christchurch, "The Wind-excited Oscillations of Suspension Bridges," by D. E. J. Walshe; Hatfield, "The Development of the Aircraft Carrier," by Copt Short and Lt-Cdr Barlow; Reading, "Hovercraft Development," by W. J. Eggington; Swindon, a.g.m. and films; Weybridge, "An Experiment in Vertical Take-off," by D. Keith Lucas (at RAeS new lecture theatre). Jan. 5, Isle of Wight, a.g.m. and film show.
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