The Curtiss C-46 Commando was one of the most important US transport aircraft of the Second World War, and survived to see service in Korea and Vietnam.
The C-46 was originally developed as the Curtiss CW-20, which was to be a twin engined civil transport aircraft intended to complete with the Boeing 247 and Douglas DC-2. Work began in 1935 and by 1936 it had been decided to produce a 36 seat passenger aircraft with a pressurized cockpit and cabin, and space for 8,200lb of
cargo. The new design had streamlined looking fuselage, with the cockpit windows built into the lines of the fuselage, avoiding the ‘stepped’ design of contemporary aircraft. The fuselage cross section was unusual, with two overlapping circular sections which met at the cabin floor level. On the CW-20T prototype the ‘crease’ where these two circular tubes met was faired over, but on most production aircraft it was left exposed, giving the aircraft a figure 8 cross section. The prototype was powered by two Wright R-2600 Twin Cyclone engines, each producing 1,700hp at take off. The prototype was built with twin fins and rudders on the tail. Work on the aircraft progressed fairly slowly, and the first prototype didn’t make its maiden flight until 26 March 1940. This aircraft was then given a new tail, with a single fin and rudder and a low mounted straight horizontal tail, and this modified design was used the production versions.
The new aircraft almost immediately attracted the interest of the USAAF, which purchased 46 in July 1940, giving them the designation C-46. In June 1941 they also purchased the modified prototype, briefly using it as the C-55 before returning it to Curtiss. The C-46 used a similar tail to the modified prototype, with a level horizontal surface and a single fin and rudder. Production of the C-46 quickly increased in scale, and 3,182 examples of the C-46 and similar Navy R5C were delivered between 1942 and 1945.
The C-46 was one of the few aircraft to fly in just about every theatre of the war, although it is most famous for its role on the ‘hump’, flying supplies into China. Although it soon became a reliable aircraft, it was rather rushed into production, so a number of flaws had to be fixed after the aircraft entered service – by November 1943 a rather impressive list of 721 modifications had been issued! The C-46 was also often used at the limits of its range and capabilities, when tended to exaggerate the impact of any flaws.
The ‘hump’ route from India and Burma into China had to be used after the advancing Japanese cut the existing ground routes when they captured Lashio, Burma in April 1942. Many different types of aircraft were used on this route, but the C-46 was one of the most successful. It had better high altitude performance than the Douglas C-47 Dakota, which was essential when flying over the Himalayas. This was one of the most dangerous transport routes of the Second World War – a 500 mile trip over 22,000ft high mountains, often in terrible weather, and well within the range of Japanese fighters.
The airlift began on 8 May 1942. The C-47 was soon found lacking, so the bulk of the work had to be carried out by the C-46 and the Consolidated C-87 Liberator Express. A target of 7,500 tons of supplies per month was set, but in December 1942 only 1,227 tons were carried, and the original target wasn’t met until October 1943. From 1 December 1942 the operation was led by the Air Transport Command of the USAAF. The scale of the operation increased massively in 1943 and by December 11,000 men were working on the hump. As a result of this effort the amount of cargo being lifted into China continued to rise, reaching 4,450 tons in August 1943, 12,590 tons in December 1943, 19,050 tons in July 1944, 32,000 tons in December 1944 and 71,042 tons by July 1945, by which point 23,000 men were involved in the operation.
The C-46s were sometimes withdrawn from the hump to support ground operations in China and Burma. Merrill’s Marauders and Wingate’s Chindits were amongst the beneficiaries of this. In November 1944 the C-46 was used to fly 18,000 Chinese troops to Kunming to protect the area against a Japanese thrust.
The ‘hump’ took a terrible toll on the aircraft involved, with nearly 1,000 lost on the route, which remained in operation until 30 November 1945. After the war the C-46 was also used to fly 47,000 US troops from around the theatre to Karachi ready for them to be flown home.
The aircraft’s long range also meant that it was better suited to conditions in the Pacific, where there were often large gaps between island airfields. The Marines also used it in the Pacific, as the R5C-1.
From 1942 the C-46 was used to fly a regular ferry route between Natal in Brazil and Accra in Ghana. This duty lasted until November 1944 when the C-46 was replaced by the Douglas C-54 Skymaster.
The C-46 arrived late in the European theatre of operations, entering serving in March 1945, just in time to take part in the massive airborne operations that supported the crossing of the Rhine.
After the war the C-46 remained in service with the USAAF, while many aircraft passed into other hands. The US Combat Cargo Command used the C-46 during the Korean War, where it was actually used on both sides – all C-46s in China at the end of the war had been purchased by Chiang Kai-shek, and many captured by the Communists.
The C-46 was used by the 1st Air Commando Group on counter insurgency operations in Southeast Asia during the 1960s, so the Second World War transport saw limited use in Vietnam.
The C-46 was also used by Japan, India, South Korea, Japan, Bolivia, Cuba, the Dominican Republic, Peru, Mexico, Brazil, Egypt and Israel. After the war many were converted into civilian transports (mainly for freight rather than passengers), and saw use by at least 350 different commercial operators!
The first order was for 46 Curtiss C-46s, to be built in the Curtiss plant at Buffalo. These used the new tail developed on the prototype. The fairing over the crease in the side of the fuselage was removed as it was found to have no aerodynamic benefit. The number of windows was reduced to four on the port side and five on the starboard side. The cabin pressurization was abandoned – it wasn’t seen as necessary in a military transport. It was powered by two 2,000hp Pratt & Whitney R-2800-43 engines driving four bladed electric Curtiss propellers. They could carry 50 troops, 33 litter patients and four attendants or 10,000lb of cargo. The first C-46 was finished in May 1942 and delivered in July 1942. However only 25 of the original 46 aircraft were delivered as the C-46, with the remaining twenty one completed as the improved C-46A.
The C-46A introduced a number of major improvements. The main floor was reinforced to allow it to carry 15,000lb of cargo, and a double door added on the port rear of the cabin. This was an upward hinged cargo door 8ft wide by 6ft 6.5in tall, with two smaller downward hinged doors built into it for passenger access. Smaller vehicles such as jeeps could be driven straight into the C-46A
Early examples used the same engine as the C-46, but this was later replaced by the similar 2,000hp Pratt & Whitney R-2800-51. These aircraft produced the same maximum power as the -43, but were better at high altitude, and played a major part in allowing the C-46A to operate over the ‘hump’, flying across the Himalayas from India to China. Forty folding troops seats were installed, with twenty on each side of the fuselage.
The C-46A was produced in large quantities, with 1,039 built at Curtiss’s Buffalo plant and 438 at a new Curtiss plant at Louisville. Two were built at St. Louis, where the prototype had been built. An order for 500 was placed with the Aircraft Division of the Higgins Boat Company at New Orleans but only two of these were completed.
The XC-46B was the designation given to a single C-46A (43-46953) that was modified in 1944 to give it a stepped windshield of the type used on most contemporary bombers and transport aircraft. It was also given more powerful 2,100hp R-2800-34W engines with water-injection to give it extra take-off power.
This designation was probably given to an aircraft that was instead completed as the first C-46G, before becoming the prototype XC-113. It may also have been allocated to another conversion carried out at St. Louis.
The C-46D was the second major version of the aircraft, with a total of 1,410 built, all at Buffalo. The main difference between the C-46A and the C-46D was the addition of an extra door on the starboard side of the fuselage. This allowed paratroops to exit from both sides of the aircraft at the same time, doubling the rate at which they could drop, and thus halving the distance covered by the aircraft during the drop. Most of the C-46Ds were used as personnel transports.
The C-46E was a minor variant, with only seventeen produced. It had the same fuselage as the C-46A, so without the extra cargo door of the C-46D, and the stepped windscreen of the XC-46B, which was believed to give better visibility for the crew. They were powered by the R-2800-75 engine while drove a three bladed Hamilton Standard propeller.
All seventeen were produced at St Louis and given 1943 serial numbers, although they were delivered in July-August 1945. A total of 550 were ordered, but the rest were cancelled after VJ Day. The type had been intended for lend lease use. After the war all seventeen aircraft were purchased by Earl F. Slick of San Antonio, Texas, who used them for four Slick Airways, which became a major airfreight firm and survived until 1966.
The C-46F was produced at Buffalo. It used the standard smooth nose, but with the R-2800-75 engines of the C-46E. It also had cargo doors on both sides of the fuselage like the C-46D. The C-46F also has squared wing tips and used three blade propellers. A total of 400 were ordered, but only 234 were completed before VJ Day and the rest of the order was then cancelled.
The C-46G was to have been the first major production version to used the stepped windscreen of the XC-46B and C-46E. It was to have the double cargo doors used on the C-46D and C-46F, and the square wing tips of the C-46F. A total of 400 were ordered, to follow the C-46F onto the production line at Buffalo, but only one was completed. This single aircraft was then flown to Columbus, where it became the XC-113 and was used to test a turbo-prop engine.
The C-46G would have been a version with a dual tail wheel and more powerful engines. 300 were ordered but the type was cancelled after VJ Day. One C-46A was converted to the C-46H standard after the war.
The C-46J was probably the designation given to an improved version of the C-46E that wasn’t ordered into production.
The XV-46K of late 1945 would have been powered by two 2,500hp Wright R-3350-BD engines, but none were produced. However the same engine was used on the XC-46L
The XC-46L was also powered by the 2,500hp Wright R-3350-BD engine, but this time three were completed, and delivered to the USAAF in 1945. The aircraft’s top speed rose to 284mph with the new engines.
The C-55 was the designation given to the original prototype after it was given the modified tail.
The C-113 was the designation given to the C-46G after it had been converted into a test bed for the General Electric TG-100 propeller-turbine.
The R5C-1 was the designation given to 160 C-46As that went to the US Marine corps in a number of batches from 1944. Most of these aircraft were used to support the island hopping campaign in the Pacific, and some remained in service after the war.
Engine: Two Pratt & Whitney R-2800-51 radial engines
Power: 2,000hp each
Span: 108ft 0in
Length: 76ft 4in
Height: 21ft 9in
Empty weight: 30,000lb
Maximum take-off weight: 45,000lb
Max speed: 270mph at 15,000ft
Cruising speed: 173mph
Service ceiling: 24,500ft
Range: 3,150 miles at 173mph