DC-2
The 1930s saw great leaps in commercial aviation. Improvements in the understanding of aerodynamics, industrial techniques and engine technology drove significant technical enhancements, while increased competition among the airlines provided the impetus for bigger and faster aircraft that could carry passengers in much greater comfort. These commercial pressures were nowhere more acute than on coast-to-coast services across the United States. Air travel remained the preserve of the rich, and airlines were always looking to shave time of the journey while simultaneously improving the customer experience. Boeing had already developed the 247 in response to these requirements, reserving the first 60 production aircraft for its partial subsidiary, United, and denying the type to competitor airlines. Transcontinental & Western Air (TWA) therefore approached Douglas to produce a specification for a three engine, 12-passenger monoplane with performance and comfort levels equal or superior to the 247. Douglas instead proposed a twin-engine design, the DC-1, featuring an innovative wing structure, the centre section of which sat beneath the cabin floor giving passengers the ability to move around the cabin without having to negotiate the wing spar. TWA signed a contract on 20 September 1932 for a single proof-of-concept aircraft, with options for an additional 60. The DC-1 made its first flight nine months later. Early trials proved the basic design, but TWA wanted greater passenger capacity so Douglas stretched the fuselage and gave the aircraft a new designation, DC-2. Discussions on production rights were held with several overseas manufacturers and this led to the assembly of 39 DC-2s in Holland and 5 in Japan. Plans for license construction by Airspeed in the UK, under the designation A.S.23, were abandoned.
First flight: 1 Jul 33 (c/n 1137, X223Y)
Production: 199 (of which 39 were shipped to Fokker and 5 to Nakajima for assembly)
First delivery: 15 Sep 33, to TWA (c/n 1137, R223Y)
Last delivery: 28 Sep 39, to US Army Air Corps (c/n 2092, 38-535)
Variants: DC-1 - proof-of-concept 12-passenger airliner, powered by 2 Wright Cyclone SGR-1820-F3 radials (1 built);
DC-2 - production version powered by Wright Cyclones (sub-types vary) with stretched fuselage, detail improvements and seating for 14 passengers (156 built, including 3 for the USAAC as XC-32 and YC-34 and 5 for the US Navy as R2D-1; first flight 11 May 34);
DC-2A - DC-2 powered by Pratt & Whitney R-1690 Hornet radials (2 built);
DC-2B (unofficial designation) - DC-2 powered by Bristol Pegasus VI radials (2 built, for LOT);
C-33 - DC-2 for the USAAC with large cargo door and enlarged vertical tail (1 built, subsequently redesignated C-38);
C-39 - C-33 with centre-section, tail unit and undercarriage from the DC-3 (35 built, often referred to “DC-2½”);
C-41 - C-39 equipped as 14-seat staff transport and powered by Pratt & Whitney R-1830-21 Twin Wasps (1 built);
C-42 - C-39 equipped as VIP transport (1 built).
Commercial DC-2s impressed into USAAC service were given the designation C-32A.
DC-3
In 1934, American Airlines approached Douglas to produce a sleeper transport that combined the performance of the DC-2 with the space and comfort of the Curtiss Condor bi-planes it was then using on its transcontinental services. Despite having only flown for the first time a year earlier, the Condor was slow and technologically obsolete: the southern route flown by American on its coast-to-coast services took longer than the more direct route flown by Transcontinental & Western, and only the superior comfort of the Condor’s sleeper service allowed American to remain competitive. Douglas was sceptical about the size of the market for such an aircraft, especially in light of the DC-2’s success and the growing daytime air transport market, but was persuaded by American’s chairman, Cyrus R. Smith, to begin work. The initial concept had been to undertake a fairly simple development of the DC-2 but studies led to a major redesign featuring a wider, longer fuselage, a new wing and tail section, as well as a strengthened undercarriage. The resulting Douglas Sleeper Transport (DST) was an instant success, prompting Douglas to cease DC-2 production in favour of the DST and its day transport equivalent, the DC-3. American’s NC16002 Flagship Illinois undertook the first commercial flight, from Midway to Newark on 25 June 1936. By the time the United States entered World War II, 430 DST/DC-3s had been delivered and, of the 322 aircraft operated by domestic airlines at the time, 260 were DSTs or DC-3s. Huge numbers for the American military followed with production eventually running to over 11,000 units. Large numbers declared surplus at the end of the War were made available to airlines to restart commercial services, and the DC-3 remains in commercial and military service in significant numbers more than 80 years since its first flight. In total, well over 900 DC-3s survive, of which more than half are active or on display.
First flight: 17 Dec 35 (c/n 1496, X14988)
Production: 11,139, comprising 10,654 by Douglas (960 at Santa Monica, CA, 4,285 at Long Beach, CA, and 5,409 at Oklahoma City, OK) and 485 in Japan (414 by Showa Hikoki Kogyo at Showa and 71 by Nakajima). An additional 4,860 DC-3s were built under licence in the Soviet Union (as the PS-84 and Li-2) at Moscow-Khimki, Tashkent-Vostochny, Kazan-Borisoglobeskoye and Komsomolsk-Dzyomgi. These aircraft are outside the scope of this publication.
First delivery: 11 Jun 36, to American Airlines (c/n 1495, NC16001)
Last delivery: 6 May 46, to Navigaçao Aerea Brasileira (c/n 42980, PP-NAM)
Principal variants: DST/DC-3 - developed and enlarged version of the DC-2 powered by 2 Wright SGR-1820-G5 Cyclones, with accommodation for up to 14 sleeper or 28 day passengers, (21 DST and 266 DC-3 built, at Santa Monica);
DST-A/DC-3A - DST/DC-3 developed for United and powered by Pratt & Whitney R-1830 Twin Wasps (19 DST-A and 114 DC-3A built, at Santa Monica);
DC-3B - DST/DC-3 developed for TWA and powered by uprated Cyclones (10 built, at Santa Monica)
DC-3D - post-war civil version, built from C-117A parts and powered by Twin Wasps (28 built, at Oklahoma City)
C-41A - DC-3 with 23-seat interior for USAAC (1 built, at Santa Monica)
C-47 Skytrain/Dakota I - military transport version of the DC-3A with large cargo door, accommodation for up to 27 troops or 10,000 lbs of cargo (965 built, at Long Beach);
C-47A/Dakota III - C-47 with 24-volt electrical system (2,954 built at Long Beach and 2,300 at Oklahoma City; 81 Long Beach and 157 Oklahoma City-built aircraft were transferred to the US Navy as R4D-5 and redesignated C-47H in 1962);
C-47B/Dakota IV - C-47A with additional fuel tanks and high-altitude turbo-chargers (300 built at Long Beach and 2,931 at Oklahoma City; 150 Oklahoma City-built aircraft were transferred to the US Navy as R4D-6, becoming C-47J in 1962; many C-47Bs subsequently had their turbo-chargers removed and were redesignated C-47D);
TC-47B - navigation transport version of C-47B (133 built at Oklahoma City, 41 of which were transferred to the US Navy as R4D-7, becoming TC-47K in 1962);
C-53 Skytrooper/Dakota II - troop transport version of the DC-3A with accommodation for 28 troops (219 built, at Santa Monica; 20 were transferred to the US Navy as R4D-3);
C-53C - C-53 with large cargo door (17 built, at Santa Monica);
C-53D - C-53C with 24-volt electrical system (159 built, at Santa Monica)
C-117A - Staff transport version with 21-seat airline-style interior, based on the C-47B but with the cargo door and strengthened floor omitted (17 built, at Oklahoma City)
R4D-1 - US Navy version of C-47 (66 built, at Long Beach)
149 commercial DC-3s impressed into USAAC service prior to delivery were given the designation C-48/A/C, C-49/A/B/C/ D/J/K, C-50/A/B/C/D, C-51, C-52/A/B/C and C-68. Impressments into US Navy service were made under the designation R4D-2 and R4D-4.
Conversions include: DC-3C - 21 C-47A/B re-manufactured by Douglas in 1946 for commercial operators (this designation was also applied generically to any surplus military DC-3 civilianised at the end of World War II, but is not used for this purpose in this publication);
DC-3S (or Super DC-3) - modernised version of the DC-3 with stretched fuselage with accommodation for up to 30 passengers, redesigned tail and revised wing, intended to be a new-build venture, but no orders received (105 converted, 100 of which were delivered to the US Navy as R4D-8, becoming C-117D in 1962; first flight 23 Jun 49);
AC-47D - 25 C-47Ds modified by Hayes Industries for airways calibration; 23 survivors redesigned EC-47D in Jan66;
FC-47D Spooky - approximately 50 C-47Ds modified as gunships, re-designated AC-47D in Jan66.
Turbine conversions: Mamba Dakota - Dakota IV re-engined with Armstrong-Siddeley Mamba engines (1 converted at Bitteswell, UK; first flight 27 Aug 49);
Dart Dakota - Dakota IV modified by Rolls-Royce for testing of Dart engines for the Vickers Viscount (1 converted at Hucknall, UK; first flight 15 Mar 50) plus two modified by Field Aviation for British European Airways cargo operations;
Turbo Three - 1 C-53 and 1 DC-3S re-engined by Conroy at Santa Barbara, CA, with Dart 7s (first flight 13 May 69);
Tri-Turbo Three - Turbo Three further modified with 3 Pratt & Whitney PT6A-45 turboprops (1 converted, by Specialised Aircraft Co at Camarillo, CA; first flight 2 Nov 77);
Turbo Express - re-engined version powered by 2 Pratt & Whitney PT6A-45R turboprops and the first to feature stretched fuselage to account for shift in the centre of gravity (1 converted, by USAC at Burbank, CA);
DC-3-65TP - re-engined version with PT6A-65s (4 converted, by Aero Modifications International (AMI) at Waco, TX; first flight 01 Aug 86). Programme subsequently sold in South Africa where the South African Air Force modified 31 aircraft as C-47TPs at Snake Valley and Cape Town-Ysterplaat. Wonderair converted 3 at Pretoria-Wonderboom from kits provided by AMI. A fourth conversion was completed by Professional Aviation as a Jetprop DC-3 and the conversion is now being marketed in the US by Preferred Airparts as the Preferred Turbine 3;
BT-67 - re-engined and modernised version, powered by 2 Pratt & Whitney PT6A-67R turboprops (72 conversions completed by Basler at Oshkosh, WI or in train; conversions continue at the rate of one every 18 months or so).