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Aviation History
1961
1961 - 1870.PDF
By D. N. MAY YS-11 More about Japan's "Twin Viscount" DC-3 Replacement AERONAUTICAL historians in Germany, Italy and Japan willmark the 1960s as the period in which their countries onceagain took their places in the forum of aircraft-producing powers. Since the war these nations have relied mainly on militaryprogrammes to develop their skills. True, they have been involved in the production of small civil aircraft, but these have never been ofa type to attract world-wide airline interest and cannot therefore be considered real advances along the road to aeronautical maturity. The development of an airliner poses problems not found inmilitary aircraft. Apart from the all-important issue of finding finance, and from the technical considerations of long life, turn-round and reliability, there is the immense problem of building up a sales team to sell the aircraft and developing a good after-salesorganization. Because of these special difficulties, it is interesting to see whichresurrected company will bring out the first successful transport. Italy's Agusta AZ-8 did not even sell in Italy. East Germany'sVEB-152 was cancelled after a fortune had been spent on it, and West Germany's HFB.314 has not been taken beyond the studystage. In fact, it seems that the only airliner from Germany, Italy and Japan which has a remote chance of succeeding is the JapaneseNAMC YS-11. Broadly speaking, the YS-11 might be seen as a twin-DartViscount. It is a low-wing aeroplane which could be mistaken for an Avro 748; but there is room for 15 rows of seats, and eachengine develops nearly twice the power of the Darts fitted in early Viscounts. The Rolls-Royce RDa.10/1 produces no less than2,775 s.h.p. for take-off, using water-methanol, and compared with the RDa.7 has 16 per cent higher mass flow, a flame-tube tempera-ture 65°C higher, and air-cooled blades in the high-pressure turbine, lncreased-capacity reduction gear, a conical spinner and 14ft 6inDowty-Rotol propellers complete the picture. Around this powerplant the Japanese designed the YS-11. In1957 the Transport Aircraft Development Association started •work, and by June 1959 they had hammered out the basic config-uration. In this month they were succeeded by the Nihon Aero- plane Manufacturing Co (NAMC), which was formed under theAircraft Industries Promotion Law with both government and private capital. Its directors came from the old-established firmsof Mitsubishi, Fuji and Kawasaki, who handle most of the pro- duction. There have been management changes, and productionis the responsibility of six manufacturers in Japan alone; but NAMC has shown that it is no novice at aircraft production. Thefirst YS-11 is due to fly this month (December) and is to enter service—after certification by the Japan Civil Aviation Bureauand the FAA—in the summer of 1963. By any standards, this is a creditable achievement. The aircraft is a short-range feederliner and has been describedas a DC-3 replacement. Its best operating costs are on routes of between 300 and 550 miles, and it is designed to use airfields thatthe DC-3 cannot. In short, it is tailored to the requirements of the East, where traffic between the small towns and big cities isincreasing, and where airfields are short, hot and often high. NAMC estimate a demand for about 150 aircraft, including 40for export (largely in the East). Basic price is £360,000. Although the YS-11 is designed to do an unsophisticated job,its structure and systems compare favourably with the latest in any country. The airframe is largely fail-safe, and should have a life ofover 30,000hr, which is adequate for a type which will take off and land at least once every flying hour. To prove these qualities, YS-11 fuselage on the production line. It is circular in section except where it blends into the flight-deck forward of the passenger door two airframes are being subjected to testing, one fatigue and onestatic load. In addition, there is the normal testing of components. The wing consists of three main sections, with the centre-sectionrunning through the underfloor of the fuselage in accordance with the theory of continuity. Construction is of the two-spar box type,and the fuel tanks are housed in the box both inboard and eutboard' of the nacelles. The outboard tanks are integral, with a capacityof 1,060 Imp gal, and they are used for all normal operations. Inboard are bag tanks, for long-range use, holding 490gal of fueland 105gal of water-methanol. This suggests an operating range of much more than 400 miles—until it is realized that the fuel issufficient for several stages; and there is enough water-methanol (which will probably not be needed at every airfield) for two take-offs. Although the YS-11 carries between 52 and 60 passengers, itsshort-haul duties keep its gross weight to 50,2501b. Maximum landing weight is 48,0001b. Standard seating is for 52 passengersat 38in pitch, but the same number at 34in pitch increases baggage space and 60 can be seated at 34in pitch. Seating is four-abreast,and there are 24 windows down each side of the unpartitioned cabin to allow changes in layout without impairing passengervisibility. Fluorescent lighting is used for cabin illumination. Toilet and galley are situated at the rear. NAMC claim an "amazingly low sound-level" for the cabin.This is due to "effective use of modern sound-proofing materials and techniques," and is not prejudiced by propeller-to-fuselageclearance, which is 2ft 2in. Cabin pressurization is maintained at a differential of 4.161b/sq in, which gives a cabin altitude of 8,000ftat 20,000ft. Superchargers installed on each engine supply the air, and with one engine out the aircraft can still be kept at its mosteconomical altitude with pressurization unaffected. To keep turn-round time low, the port engine has a hydraulicpropeller-brake, so that passengers may safely enter the aircraft through a door on the left-hand side of the forward section. Theservicing door is on the same side but at the rear, and the cargo door is opposite on the right-hand side. For emergency purposes,there are two hatches, each incorporating a window, above the wing. Normal YS-11 crew is two pilots and a stewardess. The flight-deck is neatly laid out, although access to the pilots' seats seems to be rather difficult. Communication equipment is orthodox: oneHF and two VHF transmitter-receivers, with space for an emergency radio, an additional HF and a Selcal. Navigational equipmentincludes duplicated ADF and VOR, a marker beacon and two glide-slope receivers. Space has been reserved for DMET andLoran, and space and wiring provision has been made for weather radar and autopilot. As might be expected, everything is based ontraditional US practice.
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