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Aviation History
1948
1948 - 0809.PDF
, 1948 FLIGHT SCANDIA Discussed A Swedish D.C.3 Replacement With Outstanding Performance : "In the Air" Impressions by Wing Commander Maurice A. Smith, D.F-C WHEN designers first started, a few years back, to con-sider a replacement aircraft for the ubiquitous D.C.3or Dakota, they naturally took advice on existing_ and anticipated requirements. The advice which seemed good at the time, led them in most cases to work on larger and faster designs to meet a much greater volume of air traffic forecast. The predictions have not turned out to be entirely accurate, and some of the new twin-engine transports have proved to be unsuitable substitutes for D.C.3S on many routes. To mention a few difficulties, they have too large a capacity for services of convenient fre- quency; they require better and larger airfields for safe operation than are available; and with their large engines, special equipment and high speed are a great deal more expensive to operate and maintain. The Swedish S.A.A.B. 90 or Scandia is in a class of its own among new aircraft, in being designed specifically to replace the now obsolete D.C.3. Its normal capacity is 24 passengers with luggage, although a short-range 32-seat layout is also offered. It will operate safely from small airfields, has sufficient range with full load (800 miles) to fly over any of the internal European stages, and has speed sufficient to fly across Europe on capital-to-capital services and retnrn to base the same day. In addition to the achievement of these aims, the S.A.A.B. company have laid great stress on safety and simplicity while maintaining a truly modern conception. Safety, they believe, is chiefly dependent upon first-class low-speed characteristics, and operational economy on aero- dynamic perfection and on the \ avoidance of complication. Al- though the tendency has been progressively to increase wing loading, and for high speeds to turn to laminar-flow sections, S.A.A.B. designers point out that there has been no advance in human ability or in take-off and landing technique. Therefore to conform with their safety precept, landing and approach speeds were pegged at a low level, and a well-tried N.A.C.A. wing section is employed. The Scandia's increase in wing load- ing of 30 to 40 per cent over pre-war types for similar duties, achieved without impairing low-speed qualities, has been made possible by aerodynamic advances. The Scandia is a low-wing design with pronounced dihedral, a widely spaced nose-wheel undercarriage, and oval-section fuselage. The tail surfaces are neat and appear small by comparison with other new single-fin designs. The cabin is air conditioned but not pressurized. Should a demand arise for a pressurized version it might be built, a study of the possibilities having already been made. By virtue of its good performance the Scandia could be sub- stituted at short notice for an aircraft such as the D.C.4, should bookings not justify the use of a large aircraft on a particular flight, and could maintain much the same schedules. In November, 1946, the Scandia prototype made its maiden flight with Capt. Smith at the controls. Since that time, flight development has continued and experience amounting to 270 hours in the air has been built up. The first and second production machines for Swedish airlines are now well on the way, and regular deliveries of the first order of ten S.A.A.B.90A-2S1 with Pratt and Whitney Twin- Wasp R-2180 engines, should begin in August, 1949. The later engines are not expected to
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