FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1958
1958 - 0564.PDF
580 FLIGHT ORIGINS OF THE MODERN AIRLINER . . . root and nine per cent at the tip. This thin section, which wasmade possible by the multi-cellular form of construction, helped to keep the centre-section below the cabin floor. By forestallinga general aerodynamic trend, it was to be an important reason for the long competitive life of the DC-2/DC-3 series. The DC-2had a cruising speed at 8,000ft of about 170 m.p.h. on 50 per cent of take-off power and was about ten miles per hour faster than theBoeing 247D. It was also longer-ranged, offering a maximum practical stage-length of about 1,000 miles as against 750 milesfor the Boeing. The DC-2 could carry its capacity payload for about 500 miles. As soon as the DC-2 was established in service its out-standing qualities became apparent. The type sold rapidly and American Airlines and five other U.S. domestic operatorsfollowed T.W.A.'s lead and bought DC-2s. Abroad, K.L.M. and Swissair were among the first purchasers. They werefollowed by seven other foreign airlines. K.L.M. used the DC-2 for its services between Europe and the Far East. The perform-ance potentialities of the DC-2 and, to a lesser extent, of the Boeing 247D — actually the first 247D — were dramaticallydemonstrated when an aircraft of each type took part in the historic MacRobertson Race from England to Australia inOctober 1934. The two "sedate commercial transports" gave performances almost as spectacular as those of the specially-builtracing aircraft with which they were in competition. The DC-2 flew from Mildenhall to Melbourne in an elapsed time of 3f dayswhich compared with just under three days taken by the winning de Havilland Comet racer. By the end of 1934 Douglas were producing ten DC-2s a month,and the hundredth was delivered to American Airlines on June 5, 1935. A total of 220 of these aircraft was built (160 for the air-lines) before the type was succeeded in production by the larger DC-3 in 1936. The initial development of the DC-1 and DC-2series is said to have cost rather more than $300,000 (£60,000). Production aircraft were sold at $65,000 (£13,000) each and break-even on the project is believed to have been reached after 75 aircraft had been built. Low as the prime cost of the DC-2 seemstoday, it was an expensive aeroplane compared with the Fokker and Ford Trimotors of the previous era, which had cost between$35,000 and $38,000 (£7,000-£7,600) each. While Boeing and Douglas were engaged in their competitivestruggle over the first generation of "modern" transports, a third contender appeared on the scene. In the second half of 1933, soonafter the Boeing 247 had entered service and the DC-1 had flown, the Lockheed Aircraft Company at Burbank in the Los Angelesarea started building their L-10 Electra. The Electra first flew on February 23, 1934, and quickly proved itself to be a worthycontemporary of the DC-2. It had an initial gross weight of 9,000 lb with accommodation for eight passengers and was there-fore a size smaller than the Boeing 247 and considerably smaller than the DC-2. At this stage in air transport development such asmall vehicle was still attractive for scheduled operations because of its low aircraft-mile costs, and the Electra was sold to manycommercial operators. The first Electras went to Northwest Air- ways and the second batch to Pan-American. About 150 werebuilt, together with 114 L-12s, 112 L-14s and 624 L-18s (the majority of which were supplied to the Services). All these typesderived from the original L-10 design and had passenger capacities of up to 14, or 21 in high-density layouts. Production was at arate of 35 aircraft per month by 1939. The Electra was of the sarne all-metal (24S light aUoy) stressed-skin construction as the Boeing and Douglas and, like them, was a cantilever low-wing monoplane with a rounded-section fuselageand with the passengers accommodated in two rows each side of The DC-3, which first flew in late 1935, "was to bring air transport through its most critical formative years." First flown in February 1934, the Lockheed Electra "quickly proved itself to be a worthy contemporary of the DC-2." a central aisle. The wing structure, however, featured a one-sparmethod of construction—a type which has proved less satisfactory from the fatigue-resistance aspect than the Douglas multi-spars. Adesign innovation was the adoption of duplicated vertical surfaces mounted at the tips of the tailplane. This arrangement started afashion in design to which Lockheed adhered right down to their Constellation series with its triple fins and rudders. By now as a matter of course, the Electra and the designswhich evolved from it had flaps, variable-pitch propellers and retractable undercarriages. These Lockheed aircraft were ratherfaster than their Boeing and Douglas contemporaries; and the Lockheed 14, which flew for the first time oh July 29, 1937, wasparticularly notable because it introduced the highly effective Fowler area-increasing flaps, which have since been widely used.This type of flap had been first tried in 1927 and was demon- strated on a Pitcairn design in the Guggenheim International SafeAircraft Competition of 1929. These flaps in the L-14 made possible a wing loading of 32 lb/sq ft while holding down thestalling speed to 69 m.pji. The Lockheed 14 was the first aircraft in airline service to have two-speed superchargers, featheringpropellers and under-floor freight holds—developments which were to become standard features of subsequent types. The type14 was later "stretched"—by lengthening the fuselage to take another row of seats—into the L-18 Lodestar, which first flew onSeptember 21, 1939. Tracing the story of the Electra and its successors has broughtthis account chronologically past what was perhaps the most significant of its milestones. This was the appearance of thefamous DC-3, undoubtedly the most successful airliner which has so far been produced. The DC-3 was the logical development ofits predecessor, the DC-2. Early in 1935 discussions started between Douglas and one oftheir leading DC-2 customers, American Airlines, about a scaled- up version of the earlier aeroplane to be used as a sleeper trans-port on the transcontinental routes in succession to the Curtiss Condor biplanes then in service. It was to provide sleepingaccommodation for 14 passengers. Work started on the first DST ("Douglas Sleeper Transport," later to become famous asdie "Day Plane" DC-3) in mid-1935 and the prototype flew for the first time on December 22 of the same year. Closely similar to the DC-2, being built of the same materialsand employing basically the same structure, the DC-3 retained the multi-spar wing and tail, and this form of construction was—fortuitously—to play an important part in the airframe's outstand- ing fatigue-resistant and fail-safe qualities. Individual DC-3s wereto fly as much as 50,000 hours without major rebuild and thus give evidence of a durability which more recent designs find ithard to rival. The wing area of the DC-3 was increased about five per cent over that of the DC-2 and die span was raised from85ft to 95ft by the addition of new and pointed tip sections. The wing section thus remained NACA 2215 at the root and becameNACA 2206 at the tip. Wing loading went up from 19 to 24 lb/sq ft. The widened and lengthened fuselage would take 21day passengers arranged two-abreas**on one side of a 19in aisle and in single seats on the other with seats 21in wide. Even withtwo-and-one seating die passenger was offered substantially more space than in the DC-2, the internal section of the cabin being7ft 8in wide by 6ft 6in high. An unexpected aerodynamic advan- tage of the larger fuselage was that it had a slightly better dragcoefficient than diat of the DC-2. Replacing the 700 h.p. Cyclones of the DC-2 with Cyclones orTwin Wasps of 1,000/1,200 h.p., enabled die loaded weight to be raised initially to 24,000 1b and later, particularly in militaryservice, to much higher figures. The higher engine powers were largely made possible by the rapid improvement in fuels, whichcontributed much to engine development during diis period. The result of these changes was an aeroplane which had no con-temporary rival and which established new standards of operation wherever it was used. According to Dr .Warner, its operating costper seat-mile represented an improvement of no less than 25 per cent on diat of the Boeing 247D. The first DC-3 (a DST sleeper version) was delivered toAmerican Airlines on July 11,1936, and other U.S. operators also soon ordered the type. The DC-3 covered die 2,600 miles from
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
