History of the DC3

When United Airlines ordered the Boeing Model 247, the revolutionary all-metal monoplane promptly rendered all other airliners obsolete and threatened the economic survival of many of United's competitors. Worried about losing business to United and unable to purchase the new Boeing, Transcontinental and Western Air inc. (TWA) decided to come up with a better aircraft. TWA's vice president of Engineering, Jack Frye, sent a letter to various aircraft manufacturers requesting proposals for a new airliner. One of the recipients of Frye's letter was Donald Douglas who received it on August 2, 1932. The letter (which Douglas was to later call "the birth certificate of the DC ships") said that TWA wanted to buy at least 10 tri-motor aircraft capable of carrying 12 passengers and 2 crew. It had to have a range of at least 1,000 miles at a top speed of 185 mph and be able to take off fully loaded on 2 of the 3 engines. It also asked that if the Douglas Aircraft Company was interested in the project, how long would it be before a prototype would be ready for service tests. Interestingly, no mention was made of cost.

Photo by Gavin Conroy

Until then, Douglas had specialised in military aircraft but he decided the opportunity was worth the risk of moving into the commercial market. He also knew that if he were to secure a contract, his designers would have to come up with a proposal as soon as possible. Only one week later, 2 company engineers travelled to TWA's New York office armed with plans for a luxurious new twin-engine aircraft. Once there, the plans were shown to Frye and TWA's president, Richard Robbins. Both Frye and Robbins were impressed with the initial proposal but before any formal contract was issued, they asked their technical advisor, Charles Lindberg, to inspect the plans. Lindberg thought the proposed aircraft showed promise but voiced concerns that it had only 2 engines instead of the 3 requested. He was insistent that it had to be able to take off and climb to 8,000 feet in the event of an engine failure; if this could be achieved then TWA would buy the aircraft. After some hasty "on the spot" calculations by the Douglas engineers, it was decided that this was possible and a deal was struck. Work began on the Douglas Commercial Model 1 (DC-1) shortly afterwards and following extensive design work and rigorous testing, it was rolled out of the hangar on June 22, 1933. At the time, it was the largest land based twin-engine monoplane ever built in the United States.

The DC-1 was of all metal construction with a streamlined fuselage sitting on top of exceptionally strong monocoque construction cantilevered wings. The 710 hp Wright SRG-1820-F3 engines were enclosed in streamlined NACA (the forerunner of NASA) designed nacelles that not only reduced drag but also helped with engine cooling. Hydraulically operated main gear was located in the engine nacelles and retracted to about half the diameter of the wheels. This was mainly for safety reasons, as the partially exposed wheels would help cushion the impact of a wheels-up landing. Variable pitch Hamilton Standard propellers and split trailing edge flaps assisted with takeoff and landing, the flaps also acting as a form of speed brake helping reduce the landing speed to 58 mph. A great deal of attention had been paid to passenger comfort, a detail often overlooked in previous airliners. Comfortable reclining seating mounted on anti-vibration rubber pads was provided for 12 passengers as well as a kitchen and practical washroom/toilet. Because the cabin floor was fitted to the top of the wing centre section there was no structural member intruding into the cabin, allowing more freedom of movement inside the aircraft. Extensive soundproofing led to interior noise levels that were considerably lower than any other airliner of the time. A thermostatically controlled steam boiler mounted on the engine exhaust kept the interior temperature at a comfortable 21° centigrade with the cabin air being changed every 60 seconds. In addition, self-adjustable fresh air vents were installed next to each seat. Of course, all these creature comforts would be of little consequence if the DC-1 were not structurally sound, a problem that plagued some previous airliners. Because of the lack of any sophisticated stress testing facilities and limited knowledge in all metal aircraft design, Douglas designers chose to use materials that were far stronger than necessary in many aspects of construction. The end result being that the DC-1 was not only very safe, but also extremely strong.

Photo by Bob Leask

Photo by Colin Hunter

At exactly 12:36 pm on July 1, 1933 the DC-1's wheels left the ground for the first time, marking the beginning of the end for the wood, fabric and wire airliner era. Further flight-testing followed, including the all-important single engine test (which was successful), before the DC-1 was delivered to TWA on September 13, 1933. It was not long before TWA realised that the DC-1 showed great promise and offered a chance to recapture the commercial airline market so they promptly placed an order for 20 DC-1s. The airline also requested that the aircraft incorporate several improvements that they felt were necessary. To meet TWA's requirements, Douglas decided that rather than trying to modify the existing design, it would be better to come up with a new aircraft based on the DC-1. Consequently, on May 11, 1934, the DC-2 made its first flight and was delivered to TWA 3 days later. To the casual observer, the DC-2 looked very similar to the DC-1. However, due to the availability of more powerful 855 hp Wright SRG-1820-FS2 engines, the fuselage had been lengthened by 2 feet allowing for an extra 2 passengers to be carried. The lengthening of the fuselage also altered the aircraft's centre of gravity so the position of the wings was moved rearward to compensate. Like its predecessor, the DC-2 set new levels of passenger comfort and service, including the introduction (by TWA) of the first "in-flight" movies. When compared to all other contemporary aircraft, the DC-2 was the safest, most comfortable and fastest airliner in the sky. It went on to establish 19 United States speed and distance records in its first 6 months of operation before receiving the Collier trophy for "outstanding achievements in flight" in 1935. Such was the success of the DC-2 that many airlines both in the United States and abroad rushed to place orders for the aircraft. In addition to the flood of orders for the DC-2, manufacturing rights were sold to Fokker in Holland and Nakajima Hikoki KK in Japan. A single DC-2 ended up in Russia where the design was copied, slightly altered and put into production (without a licence) as the ANT-35. A KLM Royal Dutch Airlines DC-2 (PH-AJU) was to achieve worldwide fame when, in October 1934, it was entered in the London to Melbourne air race. It followed KLM's regular 9,000-mile commercial route which was 1,000 miles longer than the official race route, made every scheduled passenger stop en-route (even turning back once to pick up a stranded passenger) and finished second, only 34 minutes flying time behind the winning custom built de Havilland "Comet" racing plane.

In an attempt to recoup some of the money that was being lost by their older aircraft, American Airlines experimentally installed sleeping berths on a Ford Trimotor. Much to their surprise it was found that some people welcomed the chance to sleep on long haul transcontinental flights, even on the slow and noisy Ford. The airline figured that if they could incorporate sleeping facilities on a more modern aircraft they would get an edge over other carriers. Cyrus Rowlett Smith, the president of American Airlines and William Littlewood, vice president of engineering, decided that the DC-2 would be ideal except they were too narrow to accommodate comfortable berths. As a result, Littlewood and his engineers drew up sketches of a larger DC-2 that incorporated the changes they wanted and then set about trying to convince Douglas on the viability of the project. Douglas was initially reluctant to commit to the idea as sales of the DC-2 were progressing well with at least 90 orders waiting to be filled and to build the modified aircraft that American wanted would involve extensive disruption to DC-2 production. Following a lengthy long distance phone call from Smith, Douglas was finally persuaded but still remained sceptical. After months of design, construction and testing, the Douglas Sleeper Transport (DST) was rolled out of the factory on December 14, 1935. Although based on (and bearing a strong resemblance to) the DC-2, the DST was essentially a completely new aircraft. The fuselage was of almost circular cross section and both longer and wider than the DC-2s. It comprised a 55 cubic foot baggage/mail hold to the rear of the cockpit with a private "Sky Room" (sometimes called the "Honeymoon Hut") for VIP passengers immediately behind this. The main passenger compartment was divided into 8 sections, each containing 2 seats that converted into the lower berths with the upper berths folding down from the ceiling. A toilet and dressing rooms were located at the rear as well as kitchen facilities capable of serving hot meals, a first on an American airliner. New sound proofing material was used to line the cabin walls, reducing the interior noise levels to less than that of a railroad car.

Photo by Alex Mitchell

Littlewood's original plan had suggested that the wingspan of the DST be increased by using a DC-2 wing with 5 foot wing-tip extensions added. Subsequent wind tunnel tests discovered that this idea resulted in a wing that was unstable to the point of being dangerous and did not provide sufficient lift. After many different designs had been tested, a completely new cantilevered wing with a narrower airfoil was used. As with the DC-1 and DC-2, the wings were exceptionally strong but in the case of the DST, a built in flexibility allowed them to "flap" by up to 5º in flight (many first time DST passengers had to be reassured by the crew that this was completely normal). The long-screw trailing edge flaps of the DC-2 were replaced by hydraulically operated ones and a new hydraulic pump was installed that could raise or lower the landing gear in 7 seconds instead of the 1 minute it took in the DC-2. As with its predecessors, the main gear didn't retract completely and was located in the engine nacelles behind the new 1,000 hp Wright SGR-1820-G2 powerplants. For added safety, the main gear was held in the up position by hydraulic back pressure meaning that if the system lost pressure, gravity would cause the gear to drop and lock into position. Further visible (and not so visible) changes included a larger tail surface, Hamilton Standard Hydromatic constant-speed variable-pitch propellers and an autopilot system. On December 17, 1935 the DST made its first flight with pilot Carl Cover at the controls and Frank Collbohm as co-pilot. The aircraft lifted off from Clover field, Santa Monica and was airborne for an hour and a half. The flight was described as "very routine", so routine in fact, that no Douglas executives took the time to watch it and no photographs of the event were taken. Further test flights followed and apart from the addition of a small dorsal fin to the tail to improve directional stability, no major problems arose.

As well as the sleeper version, specifications were also drawn up for a "Day-plane" capable of carrying 24 passengers in 8 rows of 3 seats (2 on one side of the aisle and 1 on the other). It was soon found that more baggage space would be needed to cope with the extra seating so the first row of seats was removed and the baggage hold bulkhead was move rearwards, reducing the passenger capacity to 21. It was in this configuration that the aircraft was developed as the DC-3. The removal of the Sky Room on later DC-3s allowed for additional cargo space and extra seating to be installed, bringing the total number of passengers carried to 28. Because of the ability to carry twice as many passengers as the DC-2 with only a 3 percent increase in operating costs, most airlines opted for the more profitable DC-3 over the DST with only 38 of the latter being built. Orders for the DC-3 (and, to a much lesser extent, the DST) began flooding in with American Airlines taking delivery of the first DST on April 29, 1936 followed later in the same year by the DC-3. By the end of 1936, orders for 100 aircraft had been placed by several airlines. The DC-3 was a hit with the aviation industry, earning praise as it surpassed even the DC-2 with its combination of speed, comfort and safety. Airlines worldwide were clamouring to get hold of the aircraft so in order to keep up with demand, Douglas sold manufacturing rights to Holland, Japan and Russia. Fokker was to construct the DC-3 in Holland but this never eventuated, leaving Japan and Russia as the only foreign manufacturers of the aircraft. The Japanese built the DC-3 as the Showa L2D while Russian built aircraft were initially designated the PS-84 before becoming the Lisunov Li-2 on September 17, 1942.

Photo by Craig Brankin

Photo courtesy RNZAF Kiwi Blue Parachute Display Team

The start of World War 2 led to large orders being placed by the military of various nations. The basic DC-3 design was modified for military service with the addition of an extra 6 inches to the wingspan, strengthening of the floor and rear of the fuselage and the fitting of a larger cargo-loading door. The original Wright engines were replaced with more powerful 1,200 hp Pratt and Whitney R-1830-92 Twin Wasps and a revised fuel system was installed. Put into service as a military transport and troop carrier, the aircraft received the designation C-47 with the US Army Air Force (and R4D in the US Navy). Further adaptations and modifications of the C-47 led to a plethora of different designations and suffixes such as the C-53 (a dedicated 28 seat troop transport) and C-117 (21 seat staff transport) to name just a couple. The Royal Air Force also operated the C-47 were it was given the name Dakota, this name also being adopted for the aircraft by many other Commonwealth nations. In addition to the C-47's official names, it also picked up various nicknames like "Skytrain", "Skytrooper", "Doug", "Dak" and (perhaps the most well known) "Gooney Bird".

The Royal New Zealand Air Force received a total of 49 Dakotas (comprising C-47s, C-47As and C-47Bs) between 1943 and 1945. The aircraft were the first transport type to be used by the air force and were intended to support RNZAF units in the Pacific. They equipped Nos. 40 and 41 Squadrons as well as No. 1 (Transport) OTU (Operational Training Unit) and saw service in many parts of the Pacific theatre during World War 2. At the end of the war, the RNZAF Dakota squadrons were called on to assist in the repatriation of released prisoners of war from Singapore and New Zealand servicemen from the Pacific. Aircraft of 41 Squadron also began operating a courier service between Whenuapai, Japan and England before being transferred to Malaya in 1950 for use in anti-terrorist operations. Prior to being disbanded in 1947, 40 Squadron was used for civilian domestic air services. Many of the squadron's aircraft and crews went on to work for the newly formed National Airways Corporation (NAC). The RNZAF finally retired its last remaining 6 Dakotas in June 1977.

Photo by Craig Justo

Photo by Craig Justo

Production of the DC-3/C-47 finished in 1945, shortly after the end of World War 2. By this stage, a total of 10,926 aircraft had been built, 10,123 of which were for the military. Unlike many thousands of wartime aircraft, most surplus C-47s managed to escape being reduced to scrap metal with many being used for various commercial applications from passenger services to freight carrying and even crop dusting and top dressing. Still more remained on air force inventories and were used on a regular basis. Prior to their retirement from USAF service in 1975, the C-47 was again to gain fame, this time in the Vietnam War as the AC-47D "Spooky" gunship. Nicknamed "Puff the magic dragon" (after the song of the same name), the AC-47D was fitted with three 7.62mm MXU-470A gattling miniguns firing out of the side of the aircraft. The first 2 went into service in December 1964 with a total of 25 eventually being used. The AC-47D proved very effective, however combat duties began to take their toll on the aircraft so the survivors were phased out of service in 1969 and replaced with the Lockheed AC-130 Spectre gunship.

Although the basic design of the aircraft is now almost 70 years old, hundreds of DC-3s and C-47s remain in military, commercial and private use worldwide. Many have been modernised to extend their capabilities, the most common modifications being the fitting of turboprop engines, lengthening of the fuselage and installation of new avionics and interior fittings. It is perhaps a tribute to the versatility and dependability of the DC-3 that so many remain in use today and give every intention of being around for the foreseeable future.

Photo by Gavin Conroy

Text © 2002 Stuart Russell.
"Classic Aircraft of New Zealand"