In service the Curtiss C-46 Commando proved reliable and able to carry much greater loads than the Douglas C-47 Skytrain, and the large-diameter cabin allowed awkward items to be carried. The cabin floor was strengthened to allow the airlift of light vehicles and artillery, The C-46 entered service in mid-1942 and was used initially on local duties, Its operations were soon extended to cover the South Atlantic routes supplying the Allied troops in North Africa but it was in Europe and the Far East that the aircraft was used extensively, its most famous route being over the ‘Hump’ between India and China. This consisted of mountainous passes and treacherous makeshift airfields, the cargoes often consisting of ammunition and fuel.
Originally designed in 1936 as the CW-20 (a 36-passenger pressured airliner), the twin-engine Curtiss C-46 Commando entered service in 1942 after undergoing extensive modifications for military service. These included the installation of a large cargo door, a strengthened floor, and folding troop seats. It was capable of carrying up to 50 troops, 33 wounded soldiers, and up to 10,000 lb of cargo. These characteristics, combined with its excellent climbing ability, made it ideally suited for flying over the Himalayas (“the Hump”) from India to China. A total of 3,341 were produced.
In common with its more prolific contemporary, the Douglas C-47, the Curtiss C-46 Commando was derived from a design initially developed for the civil market. Work on the Curtiss CW-20 began in 1937 when Chief Engineer George A. Page was instructed to develop a 24-34 passenger commercial airliner with a gross weight of 36,000 lbs (16329 kg) and powered by two l,600 hp (1193 kW) Pratt & Whitney R-2800 Double Wasp engines. The cabin was to be pressurised for above-the-weather operations and was to be capable of accommodating 20 sleeping berths. The latter, arranged across the width of the aircraft, dictated a wide cabin while, to overcome the drag that would have been induced by a completely circular fuselage of adequate diameter, the fuselage was designed as two segments intersecting at a common chord which effectively became the floor line. As a result the cabin was particularly capacious and, in addition to the 2,300 cubic ft (65.13 cubic m) of space in the upper segment, there was a usable volume of 455 cubic ft (12.88 cubic m) below the floor.
The prototype was built at St Louis, Missouri and powered by two 1,600 hp (1193 kW) Wright Cyclone 586-C14-BA2 engines rather than the planned Double Wasps, was first flown by Eddie Allen on 26 March 1940. Fairing plates were introduced to smooth out the join between the two fuselage segments and a twin-finned tail unit was fitted. The latter was replaced subsequently by a large single fin, presumably to correct low-speed asymmetric handling problems, and the machine was redesignated CW-20A. It was later purchased by the US Army to become the sole Curtiss C-55, and was sold to BOAC in November 1941. In the 24-seat configuration with long-range tanks it was used on long-haul routes and to link Malta with Gibraltar in 1942. It was broken up at Filton, Bristol in October 1943.
The deterioration of the situation in Europe resulted in increasing awareness of the inevitability of US entry into the war, and in September 1940 large orders were placed for fighters, bombers and transports, including 200 of a military version of the CW-20, which was designated C-46. The first 25 aircraft, built at Buffalo, New York, differed in detail from the CW-20, having fewer cabin windows and dispensing with the fuselage-join fairing plates. These had offered little aerodynamic advantage, while conferring a weight penalty of 275 lbs (125 kg) and adding to the manufacturing process. Cabin pressurisation was not included and the engines were replaced by 2,000 hp (1491 kW) Pratt & Whitney R-2800-43s.
This initial production version was followed by the C-46A which had double cargo doors, a strengthened floor and a hydraulic cargo-loading winch; 40 folding seats were fitted. The engines were 2,000 hp (1492 kW) R-2800-51s, early aircraft having three-bladed Hamilton propellers which were superseded by four-bladed Curtiss electrically-operated propellers. Production reached 1,041 at Buffalo and 10 at St Louis before production was transferred to a government-owned factory at Louisville, Kentucky where 439 were manufactured before the programme was returned to St Louis. Higgins Aircraft Inc. (A Division of Higgins Industries Inc.) of New Orleans completed two of a contract for 500 C-46As before the order was cancelled on 17 August 1944. The company owned by Andrew J. Higgins had a worldwide reputation in the building of boats prior to the government contract to construct aircraft.
The first aircraft built after the return to St Louis was the sole XC-46B with water-injected 2,100 hp (1566 kW) R-2800-34W engines and a more conventional ‘stepped’ windscreen. Meanwhile, at Buffalo, Curtiss had begun production of 1,410 C-46Ds, equivalent to C-46As but with a revised nose and doors for paratroop operations, and equipped to carry 50 men. Also produced at Buffalo were 234 C-46Fs, with R-2800-75 engines and blunt wing-tips, and a single C-46G with R-2800-34W engines and which was later to become the XC-113, a test-bed for the Curtiss TG-100 turboprop engine. The C-46G had a single cargo door, as did the St Louis-built C-46E which also featured the stepped windscreen of the XC-46B, and R-2800-75 engines driving three-blade Hamilton propellers. Only 17 were built of a contract for 550 which was cancelled after VE-Day.
The CW-20 would have been only a marginal commercial proposition in cargo configuration as, although by comparison with the Douglas DC-3 it offered twice the cabin volume, a 25 per cent increase in fuel capacity and a 45 per cent increase in gross weight, these favourable features were offset by 50 per cent greater fuel consumption and the fact that, at a gross weight of 40,000 lbs (18144 kg) the cabin could not be filled unless cargo density was less than 4.5 lb/cubic ft (16.02 kg/cubic m), a relatively low figure.
In service use, however, the C-46 was cleared to operate at a military overload weight of 50,675 lbs (22986 kg), allowing almost 6,000 lbs (2722 kg) more payload to be carried, and the cabin capacity became a considerable asset. The first of the US Army’s C-46s was rolled out at Buffalo in May 1942 and delivered on 12 July. Some of the earliest deliveries were to Air Transport Command’s Caribbean Wing (Eastern Air Lines’ Military Transport Division, formed on 1 September 1942). This used some of the first aircraft from the line to build up operational expertise, flying a military service from Miami to Middleton, Pennsylvania, commencing on 1 October, and then from Miami to Natal, Brazil, from February 1943. As the transfer of men and equipment to North Africa built up, C-46s were introduced to the South Atlantic ferry route, from Natal to Accra, Gold Coast, via Ascension Island, until sufficient Douglas C-54s became available in 1944.
Some of the early training was also carried out by the airlines, notably Northwest and Western, and USAAF schools included No. 2 OTU at Homestead, Florida and No. 3 OTU, initially at Rosecrans, St Joseph, Missouri, soon transferred to Reno, Nevada, where the local terrain was more similar to that which very many C-46 crews were to experience with the India-China Wing, flying over the ‘Hump’. These operations took place in arduous conditions, involving take-offs from primitive airfields, climbing in the vicinity of the base to more than 20,000 ft (6095 m) often on instruments in icing and turbulence, to cross mountain ranges that lay across the track while carrying hazardous cargoes, including fuel and ammunition.Burma Hump
The Curtiss C-46 Commando is best known as the mainstay of the massive air transport supply effort undertaken from the Assam region of India to supply friendly forces in south-west China. Flying the ‘Hump’, as this treacherous crossing of the Himalayan mountains became known, was a task fraught with peril for the men and C-46s of Colonel Edward H. Alexander’s India-China Wing of ATC (Air Transport Command). The aircraft were loaded and flown under the most primitive conditions, their fuel pumped by hand from drums, the Assam airfields largely unpaved and transformed into quagmire by monsoons which poured down half the year. On the 500 mile (805 km) Assam-Chunking route, C-46s had to haul cargo over ridgelines looming at 12,000 to 14,000 ft (3660 to 4265 m), even though ice began to form on the wings at 10,000 ft (3050 m). In August 1942, using a few C-47s, the USAAF had been able to transport only 170,000 lbs (77110 kg) of cargo over the India-China route but by December 1943, with many C-46s now starting to take over the route as well, the figure rose to 25.18 million lbs (11.42 million kg). Short on spare parts, flying in unbearable wet and cold with minimal navigation aids, taking off at maximum overload weight, the C-46 crews were a lifeline to Chiang Kai-shek’s Chinese forces and General Claire Chennault’s 14th Air Force at a time when the Japanese were active all around. During one of these flights Captain Wally A. Gayda shot down at close range a Japanese fighter, apparently a Nakajima Ki-43, by firing a Browning automatic rifle through his C-46 front cabin window and killing the pilot.
Span: 108 ft. 0 in.
Length: 76 ft. 4 in.
Height: 22 ft. 0 in.
Weight: 51,000 lbs. max.
Engines: Two Pratt & Whitney R-2800s of 2,000 hp ea.
Maximum speed: 245 mph.
Cruising speed: 175 mph.
Range: 1,200 miles
Service Ceiling: 27,600 ft.