The Douglas C-47 Dakota
The "Douglas DC-3" airliner was a milestone of aviation, the basis for the introduction of practical commercial airline service in the 1930s. It achieved another major distinction in military service as the "C-47 Dakota" transport. General Dwight Eisenhower described the C-47 as one of the four machines that won World War II, along with the bulldozer, 6x6 truck, and the landing craft. This document provides a history and description of the C-47.
Origins: Douglas DC-1 / DC-2 / DC-3
In the early 1930s, Boeing introduced a landmark aircraft, the Boeing "Model 247", that did much to advance the state of the art of commercial airliner technology. The Boeing 247 entered service with United Air Lines. In 1932 Trans World Airways (TWA), bumped by Boeing to second priority behind United for delivery of Model 247s, contacted Douglas Aircraft to obtain a comparable airliner.
Donald Douglas SR put his crew to work on the project, and on 1 July 1933 the "DC-1 (Douglas Commercial 1)" took to the air for the first time. The DC-1 was a low-wing monoplane, with a capacity of 12 passengers, and twin Wright Cyclone R-1820 air-cooled radial engines driving three-bladed propellers. The TWA request had specified three engines, but Douglas managed to convince TWA's technical advisor, Charles Lindberg, that two would do the job.
The DC-1 was an all-metal aircraft, except for some fabric-covered control surfaces; and it was a "taildragger", with the main gear partially retracting forward into the engine nacelles, and a nonretractable tailwheel. It was effectively a prototype and only one was ever built. It was used by TWA for promotional flights and eventually ended its days in Spain.
The production aircraft was the "DC-2". It had the same general configuration as the DC-1, but it was stretched to carry 14 passengers and had more powerful Cyclone engines. It also added rubber pneumatic de-icing boots to the leading edges of all flight surfaces. TWA ordered an initial batch of 25 DC-2s. The DC-2 first flew on 11 May 1934, and entered TWA service a week later. It proved to be a popular aircraft, with several hundred built in all, and laid the groundwork for a derivative that would become truly famous, one that would reduce the groundbreaking Boeing Model 247 to relative obscurity.
In 1934, American Airlines (AA) was considering a US transcontinental air service. Given the flight speeds of the time, that implied passenger sleeping facilities on the aircraft, and so AA asked Douglas to build an enlarged version of the DC-2 that could accommodate sleeping berths.
Douglas was scrambling to meet orders for the DC-2 at the time and was reluctant to move off in another direction, but the company took the contract. Douglas developed a new version of the DC-2 that had greater wingspan, enlarged tail, longer fuselage, and fuselage width increased by 66 centimeters (26 inches). The new aircraft could accommodate 16 sleeping berths, or 28 seats. Fitted with berths, it was known as the "Douglas Sleeper Transport (DST)". Fitted with seats, it was known as the "DC-3". This document will refer to the type as the DC-3 for simplicity, though production totals include some DSTs.
The first DC-3 flew on 17 December 1935, the 32nd anniversary of the Wright Brothers' first powered flight. The first production aircraft was handed over to AA in June 1936 to begin flight services between New York and Chicago. Intercontinental services began in September 1936.
Initial production versions of the DC-3 used Wright R-1820-G5 Cyclone engines with 685 kW (920 HP) each. The DC-3A featured Pratt & Whitney (P&W) R-1830 Twin Wasp radial engines with 746 kW (1,000 HP) each, and the DC-3B featured Wright R-1820-G-102 Cyclones with 820 kW (1,100 HP) each. The DC-3 quickly eclipsed the DC-2. By the time the United States entered World War II in December 1941, 430 DC-3s had been delivered, and that was only the beginning.
Douglas C-47 Dakota Origins
The US Navy was the first American military service to buy a Douglas Commercial transport, with the Navy purchasing a single DC-2 in 1934 and designating it the "R2D". The service later bought four more DC-2s as "R2D-1s".
In 1936, the US Army Air Corps (USAAC) service ordered a single DC-2 for evaluation purposes. This aircraft was designated "XC-32". The favorable evaluation of the XC-32 led to an order for two "YC-34s", featuring minor changes as specified by the USAAC, and then 18 "C-33s", which had a taller tailfin and a cargo door.
One of the C-33s was refitted with a DC-3 tail for evaluation purposes and redesignated "C-38". This evaluation led to a USAAC order for 35 "C-39s", which featured additional DC-3 components, such as landing gear and uprated Wright R-1820-55 Cyclone engines. The first C-39 went into service in 1939.
A few C-39s were modified to other configurations. One was fitted in production with Pratt & Whitney R-1830-21 Twin Wasps and designated "C-41". Another C-39 was similarly fitted in production with uprated Wright R-1820-53 Cyclones and designated "C-42", with two more C-39s converted in the field to C-42 standards.
The USAAC impressed 24 DC-2s into service in 1942, giving them the designation "C-32A". The DC-2 variants in military service had active lives early in the war, with some serving in the US evacuation from the Philippines to Australia in December 1941.
|MILITARY DC-2 SUMMARY TABLE|
|YC-34||2||Army||Minor Changes From Production DC-2.|
|C-33||18||Army||Added Cargo Door And Taller Tailfin.|
|C-38||-||Army||C-33 Fitted With DC-3 Tail For Evaluation.|
|C-39||35||Army||DC-2 With DC-3 Tail, Landing Gear, Etc.|
|C-41||-||Army||C-39 Refitted With P&W Twin Wasp Engines.|
|C-42||-||Army||3 C-39s Fitted With Uprated Cyclones.|
|C-32A||-||Army||24 DC-2s Pressed Into Service During WWII.|
The DC-2's military service paralleled its civilian history, for though the C-32s and other variants of the type were good aircraft in their own right, their main importance was to pave the way for an even better machine. Given favorable impressions of the DC-2, the USAAC was clearly interested in the improved DC-3.
Development of the C-41 variant of the DC-2 for the Army had proven some of the modifications required for a militarized DC-3, and in 1940 the USAAC awarded initial contracts to Douglas for the delivery of such an aircraft. Two main variants were ordered, including the "C-53 Skytrooper" paratroop transport, of which more is said in the next section, and more significantly the "C-47 Skytrain". Douglas was heavily committed to the production of the DB-7 bomber, predecessor to the A-20 Havoc, at the company's Santa Monica, California, plant, so a new production facility was opened at Long Beach, California.
In late 1941, the first C-53s were delivered to the Army Air Forces (which had superseded the Air Corps in June), and were followed by the first C-47s in early 1942. The initial production version was simply referred to as the "C-47", and 953 were built. The basic configuration of the C-47 was much like that of the DC-3, but the engines were uprated to supercharged P&W R-1830-92 Twin Wasps with 784 kW (1,050 HP) each; the span was increased by 15 centimeters (6 inches); the fuel tanks were rearranged; the floor was reinforced to handle heavy cargoes; and a navigation astrodome was added behind the cockpit.
The most visible change was fit of a double cargo door into the rear left side of the fuselage, with a passenger door nested inside the right half of the cargo door. In a sense, the cargo doors were the aircraft's worst feature. They worked as specified, but since the C-47 was originally designed as a commercial transport, it was not optimized for loading cargo as a aircraft with nose or tail doors would have been. Getting large cargoes in and out of a C-47 could be time-consuming and frustrating; a jeep could be driven up a ramp into the aircraft, but it had to be manhandled around to fit inside the fuselage. Although the C-47 would become arguably the most famous cargolifter of all time, it was strictly an improvisation in that role.
The interior could be set up to handle cargo, paratroops, or casualty stretchers. In the cargo role, the interior was fitted with pulleys for moving up to a total of 2,720 kilograms (6,000 pounds) of cargo. For paratroop operations, the interior was fitted with 28 fold-down bucket seats hinged to the the walls. In the medical evacuation ("medevac") role, the interior was fitted with accommodations for 18 stretchers and three medics. Six parachute containers could be attached to racks under the fuselage and released for airdrop supply missions.
Douglas C-47 Development and Service
With the entry of America into the war in December 1941, USAAF demands for the C-47 skyrocketed. Civilian DC-3s were pressed into military service, and airliners in production were diverted to the USAAF, where they would would be given a bewildering list of different designations, including "C-48", "C-49", "C-50", "C-51", "C-52", "C-68", and "C-84", most of which had a number of subvariants as well. There seems to have been few differences between these machines.
However, even if the military had snapped up every DC-3 built to that time, it wouldn't have come close to meeting demand, and Douglas set up a second production line in Tulsa, Oklahoma. The first production model rolled out of the Tulsa plant was designated "C-47A", which differed from the original C-47 mainly in having a 24 volt DC instead of a 12 volt DC electrical system. Tulsa eventually built 2,099 C-47As, while Long Beach built another 2,832.
|DOUGLAS C-47A DAKOTA|
|Wingspan||29 meters||95.14 feet|
|Wing area||91.69 sq meters||987 sq feet|
|Length||19.60 meters||64.30 feet|
|Height||5.16 meters||16.93 feet|
|Empty weight||7,700 kilograms||17,000 pounds|
|MTO weight||11,800 kilograms||26,000 pounds|
|Max speed||370 kmh||229.91 mph|
|Max cruise speed||298 kmh||185.17 mph|
|Service ceiling||7,070 meters||23,200 feet|
|Range||2,410 kilometers||1,500 miles|
|Engine type||P&W R-1830-92 Twin Wasps|
|No. of Engines||2|
The last major production model was the "C-47B", which had still further uprated P&W R-1830-90 or R-1830-90B Twin Wasp engines with two-stage superchargers for high-altitude operation. This requirement apparently surfaced because of the need to fly supplies from India to China over the Himalayas, or the "Hump" as it was called. Tulsa built 2,808 C-47Bs, plus 133 "TC-47B" navigational trainers. Long Beach built 300 C-47Bs as well. In practice, the C-47B wasn't entirely satisfactory, with the Curtis C-46 becoming the champion of the Hump flights, and many C-47Bs were converted to the "C-47D" variant by removal of the high-altitude blower system.
About 219 of the specialized C-53 Skytrooper paratroop carrier version were also built. They lacked the double doors and reinforced floor, and were fitted with metal seats for 28 paratroopers and an attachment point for a combat glider tow rope. As mentioned, C-53 deliveries preceded deliveries of the C-47, and it was closer in configuration to the original DC-3 than the C-47.
A single "XC-53A" was built as a prototype. It was followed by eight winterized "C-53Bs", with additional fuel capacity; then a batch of 17 "C-53Cs" with a larger passenger door; and finally about 159 "C-53Ds" with a 24-volt DC electrical system. The glider tow attachment later became standard in C-47 production.
The USAAF also ordered a batch of military passenger transport variants of the DC-3 and gave them the designation "C-117". The C-117 had DC-3 style airliner fit and various small features added from current C-47 production, but only one C-117A and sixteen C-117Bs from the order for 131 were actually built, with production terminated by the end of the war in the Pacific.
Two particularly interesting C-47 conversions were the "XC-47C" floatplane and the "XCG-17" heavy cargo glider. The XC-47C had a pair of big Edo Model 78 floats, with each float having front and back retractable wheels and a 1,140 liter (300 US gallon) internal fuel tank. A number of such conversions were made in the field, and interestingly one of these aircraft has survived to the present.
The single XCG-17 made was modified from a stock C-47 to meet a requirement for a heavy cargo glider. Early tests were performed on a C-47 performing "deadstick" landings, and then the engines were pulled out and the nacelles faired over. The nacelles were not removed since the USAAF wanted to be able to reconvert the gliders back into powered C-47s if the need arose. The XCG-17 had an excellent glide ratio, a tribute to the DC-3's clean design, but the Air Force did not go ahead with the concept.
About 600 C-47s and C-53s from the total production were obtained by the US Navy and Marine Corps under the designation "R4D", with variant designations as follows:
The Navy and Marine Corps also flew a number of specialized modifications of stock C-47s and C-53s:
- R4D-4Q, R4D-5Q, & R4D-6Q: Radar countermeasures aircraft.
- R4D-5E & R4D-6E: Specialized electronic mission aircraft.
- R4D-5L & R4D-6L: Winterized aircraft, usually fitted with skis.
- R4D-5R & R4D-6R: Cargo variants modified for passenger service.
- R4D-5S & R4D-6S: Air-sea warfare trainers.
- R4D-5T & R4D-6T: Navigational trainers.
- R4D-5Z & R4D-6Z: VIP transports.
The British were particularly enthusiastic users of the DC-3 and its variants. A few commercial DC-2s and DC-3s were purchased or pressed into military service early in the war, and eventually were given the name "Dakota". This eventually became, more or less, the accepted name for all military DC-3 versions, though the US name of "Gooney Bird" was a strong competitor.
The British eventually received over 1,900 more Dakotas from total production through Lend-Lease, including:
- Over 50 "Dakota Mark Is", equivalent to the C-47.
- About 9 "Dakota Mark IIs", equivalent to the C-53.
- 962 "Dakota Mark IIIs", equivalent to the C-47A.
- 896 Dakota Mark IVs, equivalent to the C-47B.
Roughly 200 Dakotas of various types were passed on to the Royal Canadian Air Force (RCAF), which put them to good use. The different versions of the DC-3 in Allied military service will all be generally referred to as "C-47s" in the rest of this document, though as the discussion in this section shows, this is an oversimplification.
Soviet Lisunov LI-2 / Japanese Showa L2D
The Soviets manufactured almost three thousand DC-3 variants under license. They were built under the direction of Boris Lisunov, who had acquired his education in putting together the aircraft at the Douglas Santa Monica plant during a stint there from 1936 through 1939. The type went into production as the "PS-84", meaning "Passenger Aircraft from State Factory (GAZ) 84", and was in principle to be used as a civilian airliner by Aeroflot. After the Nazi invasion of June 1941, GAZ-84 relocated to Tashkent in Central Asia, and the aircraft acquired the military designation "Li-2".
Although the Soviet plan had been to avoid changes in the design, many tweaky modifications were incorporated in the Lisunov-built machines. The Li-2s featured:
- A slightly smaller span.
- Provisions for ski landing gear.
- Structural reinforcement and thicker skin for vulnerable sections of the airframe.
- Some rearrangements of windows.
- The main passenger door on the right.
- Soviet-built radial engines. Sources differ maddeningly on exactly which engines, but one prominent powerplant was the Shvetsov ASh-62, a 9 cylinder radial with 746 kW (1,000 HP). Apparently, the power ratings of Soviet engine fits to the Li-2 lagged those of Western C-47s and the Li-2's performance lagged accordingly.
Li-2 variants included:
- Li-2P: Basic civil passenger model.
- Li-2G: Basic civil cargo hauler, with reinforced floor and tie-downs, plus cargo doors on the left.
- Li-2PG: Civil convertible passenger-cargo version.
- Li-2T: Militarized Li-2G, with a capacity of 20 troops or 15 stretchers along with the crew of four. Some were fitted with a dorsal turret with either a ShKAS 7.62 millimeter (0.30 caliber) or UBT 12.7 millimeter (0.50 caliber) machine gun, and a ShKAS machine gun could be fitted to a flexible mount on each side of the aircraft. Bomb racks could be fitted under the fuselage, with typical carriage consisting of four FAB-250 250 kilogram (550 pound) bombs; and six RS-82 82 millimeter (3.2 inch) unguided rockets could be carried under each outer wing.
- Li-2D: Paratrooper version of the Li-2T, with a glider tow hook and paratrooper kit. Late models had a glazed front left crew door with a bulged window to allow observation of parachute drops. A long-range "Li-2DB" variant was built, with additional fuel tanks.
- Li-2R: Survey or "reconnaissance" version, with bulged windows behind the cockpit.
- Li-2V: Postwar version with turbocharged engines, used for Artic meteorological work.
In the postwar period, the Li-2 was given the NATO codename "Cab". The career of the DC-3 / C-47 wearing the Red Star remains very obscure in the West and such details as are available tend towards the contrary and untrustworthy. Hopefully more and better information will be available in the future.
Very surprisingly, DC-3s were also built in Japan during the war. Two Japanese trading firms, Mitsui and Far Eastern Trading, bought a total of 20 Douglas-built DC-3s, which went into service with Dai Nippon Air Lines and served through the war.
In 1938, Mitsui went on to obtain a manufacturing license for $90,000 USD in 1938, not bothering to tell Douglas that they were doing so at the request of the Imperial Japanese Navy. Mitsui obtained all specifications, and then also bought two unassembled DC-3s from Douglas as manufacturing pattern machines. Mitsui arranged delivery of the unassembled machines to the Showa company, which was to cooperate with Nakajima for manufacture.
The two unassembled DC-3s were put together by Showa and delivered in October 1939 and April 1940, with the designation "L2D1". In the meantime, Showa and Nakajima had been working to modify the design to use 764 kW (1,000 HP) Mitsubishi Kinsei 43 radials in place of the US-built engines. This resulted in the first Japanese production variant, the "L2D2". Nakajima built 71 of this model, delivering the last in November 1942, when the company got out the business of building DC-3 clones.
However, Showa remained in the trade, and in fact the Imperial Japanese Navy selected the type as their standard transport aircraft. Showa delivered their first L2D2 in March 1941, quickly moving on to improved variants.
The "L2D2-1" was a cargo hauler, with a reinforced floor and cargo doors on the left side of the rear fuselage. The "L2D3" was an improved passenger version, with Kinsei 51 radials providing 970 kW (1,300 HP) each and cockpit windows distinctively extended back along the fuselage. An equivalent cargo version, the "L2D3-1", was also built. Both these variants were later built with improved Kinsei 53 engines, also with 970 kW (1,300 HP), and designated "L2D3a" and "L2D3-1a" respectively.
The "L2D4" was an armed variant, with a top gun position mounting a single 13 millimeter gun, and a single 7.9 millimeter gun firing from a hatch on each side of the aircraft. The "L2D4-1" was the cargo transport equivalent. Neither went beyond prototypes. The last in the series, the "L2D5", was basically an L2D4 that was designed to be built with as much non-strategic materials (wood and steel version aircraft alloys) as possible and powered by Kinsei 62 radials, with 1,165 kW (1,560 HP) each, but the prototype was not completed before the end of the Pacific War.
Showa built a total of 416 L2Ds, in addition to the 71 built by Nakajima. The L2D was codenamed "Tabby" by the Allies. It created a degree of confusion that apparently led to some deadly "friendly fire" incidents.