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Aviation History
1937
1937 - 0913.PDF
APRIL 8, 1937. NASCENT GIANTS America Develops a Four- Engine Complex : Sub- Stratosphere Services in Sight : An Ambitious Pro gramme by Boeing SINCE Imperial Airways demon strated the practicability of large four-engined aircraft in every-day service the big air lines of the world are becoming four-engine-conscious. The trend to quadruple power plants, of course, would have been inevitable in any case. Operators are demanding in creased payload capacity in machines for trunk line service, which means that designers must seek more power. The highest-rated engines available for com mercial use deliver between 1,000 and 1,200 h.p., and in the Douglas D.C.3 we see demonstrated performance approach ing the ultimate which may be expected from such units when used in pairs on transport aircraft. Triple engines mean inferior efficiency to the technician, and increased discomfort to passengers (despite the fact that some of the most popular commercial types—e.g., the Junkers Ju.52—have had a nose engine in addition to those on the wing), so the pen dulum seems to be swinging toward the four-engined arrange ment. It may be recalled that experts representing Transcontinental and Western Air, American Airlines, United Airlines, Pan American Airways and Eastern Air Lines pooled their know ledge to aid in the designing of a large four-engined transport aircraft to be constructed by the Douglas company. Reports indicate that there have been technical hitches and that con struction is behind schedule, but that the first machines should be in service in a few months. The D.C.4 resembles, essentially, a scaled-up D.C.3 with four engines (Wright Cyclone Gs or Pratt and Whitney Twin Wasps), but with wings of a different plan form. The most striking feature is the tail unit, which seems to have triple fins and rudders, one placed centrally and the others at the tips of the tailplane. Carrying a crew of five, the D.C.4 wiU have space for forty passengers, its gross weight being in the neighbourhood of 30 tons. The span and length will be 138 ft. 3 in. and 97 ft. respectively. A maximum speed of 237 m.p.h. is expected, and the cruising range should be about 2,200 miles. The land ing speed seems on the high side at 68.5 m.p.h., and the ceiling is calculated to be 24,000 ft. Pan American Airways and Transcontinental and Western Air, presumably unwilling to wait for the D.C.4, have placed orders with the Boeing concern for a number of machines to meet similar requirements. The first two of the new craft will be special models for Pan American Airways, and will differ from the six 307s ordered by T.W.A. in that they will be equipped for continuous opera tion at 20,000 ft. Pan American has an option on seventeen of the first batch of twenty-five standard 307s to be built by Boeings. It has been agreed that after the two'P.A.A. high altitude machines have completed 500 hours' flying their special equipment will be made available for all Boeing 307s. Basically, the 307 is a four-engined low-wing monoplane with four G-type Wright Cyclones mounted forward of the leading e dge. The engines will give 1,100 h.p. for take-off and 950 h.p. for continuous operation, and the aircraft will weigh over 21 tons, being equipped to carry thirty-two passengers for day time operation, and to be fitted with eighteen berths and eight seats as sleepers. The wing span will be about 107 ft. It is believed that in a number of features it will resemble the 2 99 or Y1B-9 bombers, thirteen of which are being delivered to the U.S. Army Air Corps. At 20,000 ft. the special Pan American 307s will cruise on 75 per cent, power at 266 m.p.h. There is a possibility that FLIGHT. 347 Commercial Aviation The Ensign's U.S. counterpart : A drawing indicating certain of the salient features of the Boeing 307, some details of which are given in the accompanying matter. these aircraft will be used experimentally for transatlantic work. Their cabins, when used for high-altitude passenger carrying, will be supercharged to a pressure of 6 lb./sq. in., although it is planned in the early stages to use not more than 2J lb. pressure. This figure will be sufficient, it is claimed, to provide at 20,000 ft., and even higher, conditions experi enced in a conventional transport aeroplane flying at 8,000- 12,000 ft. The service ceiling of the special high-altitude type of 307 will be 35,000 ft. The supercharger used to feed the cabin will be a mechanical type and will draw air through an intake valve well out along the wing, whence it will be pumped inside the wing structure through a miniature air-conditioning plant near an inboard engine and thence into the sealed cabin. Ducts will distribute it uniformly from the control cabin through the passenger compartments and into an "anti-pressure" chamber in the rear of the fuselage, where the exhaust valves are located. The complete set of dual superchargers will require only a small fraction of the power of one engine. The supercharging elements and cabin pressure equipment alone will cost forty thousand dollars. It is known that the Glenn L. Martin company has been doing a considerable amount of research work on the question of high-altitude operation, and at the recent annual meeting of the Institute of Aeronautical Sciences Mr. McDonnell of that concern showed a drawing of a projected four-engined transport, generally similar to the Douglas and Boeing in con ception, but embodying twin fins and rudders after the Lock heed manner. Super Charter OLLEY AIR SERVICE have been asked by Sir Hugo Cunliffe-Owen to provide the crew for the Clyde Clipper, which has been entered for the New York-Paris race. This crew will consist of a captain, first officer and radio operator. Meanwhile, Olleys appear, from all accounts, to be going ahead with their plans for the Scilly Islands service, which was first considered by Sir Alan Cobham a couple of years ago. Useful Co-operation THE Percival Vega Gull which has recently been delivered to De Havillands for airscrew demonstration work, is the first production machine in this country to be fitted with a constant speed D.H. v.p. airscrew. The Vega Gull has been chosen largely because its four-to-one speed range makes it an eminently suitable type for such demonstrations—and it can carry three observers, with the pilot, in comfort.
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