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Aviation History
1956
1956 - 1076.PDF
222 FLIGHT, 10 August 1956 "BIG SIX" DECADE A Short History of the Douglas DC-6 Series By DENNIS M. POWELL, F.R.G.S. The first DC-6 prototype—designated XC-112 by the U.S.A.F.—airborne on its maiden flight on February 75, 7946, by Douglas test pilots John F. Martin and George Jansen. TEN years ago last August the prototype Douglas DC-6 wasnearing the end of its flight trials; it had first flown onFebruary 15, 1946. The remarkable achievement of Donald Douglas and his company in the continuous productionof a seemingly endless line of history-making transport aircraft— from the DC-2 onwards—amply justifies the slogan "More peoplefly Douglas than by all other airliners combined." It is certainly no idle boast. In the highly competitive business of furnishing a majority ofthe world's most famous airlines with four-engined pressurized long range transports, Douglas and Lockheed, with theirDC-6/DC-7 series and Constellation/Super Connie series respectively, have been the greatest of rivals since 1946. Tenyears later one finds that element of competition as great as ever with official announcements regarding the latest sales of DC-6Bsand DC-7s, and Super Constellations series 1049G and 1649A to a large number of major airlines throughout the Westernworld. By the end of 1955 about 450 DC-6 series (including theDC-6B and DC-6 A Liftmaster Freighter series) were in opera- tion by 13 American and 18 other airlines outside the U.S.A.About one hundred DC-6Bs are still to be delivered to several airlines, whilst most of the 200-odd ordered progressively since1951 have been delivered and are in service at the time of writing, a total of about 30 of the freighter version known as the DC-6Aare flying and on order for Slick Airways Inc., Flying Tiger Line Inc., American Airlines Inc., K.L.M., P.A.A., Sabena and Cana-dian Pacific Airlines. The total number of commercial DC-6As delivered to date is 24 in addition to which it is believed about 200of the military versions of the type have been supplied to the U.S.A.F. and U.S. Navy. Service designations are C-118 andR6D-1 respectively. Original design of the DC-6 was begun late in the war years,primarily for a commercial transport, but existing conditions prevented any production for commercial use taking place at that time. Instead, a prototype was built as a military transport forthe U.S.A.A.F., was designated the XC-112 (C.N.42881), and made its first flight on February 15, 1946, with test pilots JohnF. Martin and Geo. Jansen at the controls (the same Douglas pilots, incidentally, who flew the second prototype SkymasterDC-4A on its first flight early in 1942). Following successful flight trials and C.A.A. type certification of the second prototypebuilt (c.n.42854 NX90701), deliveries of the commercial DC-6 began early in 1947, with the first production aircraft going con-currently to United Airlines and American Airlines, since these two companies were the first to order this type. Later deliverieswere made to Braniff, Delta, National and P.A.A.-Grace, whilst the first aircraft supplied to a foreign airline went to Sabena, whobought three. Other early buyers were K.L.M. (7), S.A.S. (13), Aerolinas Argentina (6), Philippine Airlines (5), B.C.P.A. (4),C.M.A. (Mexico) 3, and L.A.I. (Italy) 3. Several of these air- lines subsequently took delivery of additional DC-6s and DC-6Bs.American and United Airlines were by far the largest original customers, the former purchasing 50 and the latter 45 DC-6srespectively. These two airlines, together with P.A.A., also have the largest DC-6B fleets flying today. P.A.A. operate a total of45 DC-6Bs, which they call "Super Sixes." The older DC-4 having completed over a billion miles offlying (mostly during the war), it was natural that a great deal of the vast operating experience derived from this thoroughlyproven airframe was built into the new larger, more powerful and luxurious DC-6. In exterior appearance both types aregreatly similar: the DC-6's fuselage is 7ft longer than that of the DC-4 and is fully pressurized. The standard DC-6 is some24,900 lb heavier in laden weight—although this figure is increased to 37,000 lb in the case of the latest DC-6B series. Span for bothtypes is 117ft, but the wing of the DC-6 being slightly modified. The most recognizable exterior feature of the DC-6 is, of course,its square-shaped windows, in contrast to the port-hole type familiar in the case of the DC-4. The fuselage is a semi-monocoque struc-ture of traverse frames and longitudinal stringers with an Alcad sheet skin. Thewing centre-section has three spars which pass through the fuselage and are perma-nently attached to it, whereas the two inter sections are single-spar units. Both centreand outer sections have firmer ribs, span- wise stringers and Alcad covering.N.A.C.A.-type slotted flaps extend along the trailing edge of the wing from fuselageto aileron, both ailerons and flaps being single-span structures with metal covering.Engine nacelles are all carried in the centre section. Fin and tailplane are two-sparAlcan-covered structures; die rudder is a single-spar unit with fabric covering, asare the elevators. The retractable under- carriage has twin wheels on a single shock-strut, thesa retracting forward into the inboard engine nacelles and being enclosedby twin doors. The single nosewheel is fully steerable and retracts forward into the nose. Seen here at Santa Monica is N.37507 (C.N.42872) "Mainliner Portland." one of the earliest DC-6s for United Airlines. This air- craft, like a number of others that have been flying with United and American Airlines since 1947, has logged about 30fl00 airframe hours.
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