The prototype was powered by two 1.700 hp Wright Cyclones and was aimed at the 24 to 34 seat market (while also able to reconfigure into 20 sleepers). The width of the fuselage was presumably such as would permit the berths fitted across its width and still leave room for a corridor ! In order to be able to pressurize the cabin, the designers had to strengthen the fuselage and this led to a circular cross-section for the fuselage. To have used one complete circle for the fuselage would have led to immense dimensions and too much drag. This was solved by the "double bubble" design and led to the typical shape of the C-46.
The upper segment, the cabin, proved to be cavernous for those days...
Compared to the Douglas DC-3, the CW-20 offered approximately 45 % higher gross weigth, while the fuel capacity of the Curtis Wright CW-20 was 25 % greater. Unfortunately, the fuel consumption was 50 % more and thus it fell short in the aim to increase the range of the airliner. The premier routes were the long haul transcontinental services and with the large capacity, strong performance of the engines and the ability to climb over the weather, the CW-20 must have been aimed at that market. But the lack of range was crucial.
In fact, the high fuel consumption severly limited the maximum payload and thus the large volume could not be put to optimum use by cargo operators ! But anyway, the air cargo and mail tonnage available in pre-WWII days could not support all-cargo operations in aircraft the size of the CW-20.
Curtiss was famous for its fighter designs for the US Navy as well as the Army Air Corps, starting with the P-36 in 1935 and continuing through to the P-40. The CW-20 was by far the largest project Curtiss had ever undertaken.
The prototype, registered as NX-19436, was first flown on 26 March 1940. It initially had a twin-tail configuration, but within a year this was modified to the familiar single tail layout.
By the middle of 1940, the war situation in Europe had deteriorated and the US military foresaw the involvement of the USA in what was to become World War 2. An unprecedented large amount of transport aircraft were ordered: 200 C-46s and 545 C-47s. Other types ordered in large numbers included A-20, B-24, B-26, P-38, P-40 and AT-6.
The US Army Air Corps was renamed US Army Air Force (USAAF) on 20 June 1941.
Adapting the CW-20 to military service as the C-46 Commando needed few changes. The first 25 aircraft, designated C-46, were built essentially to the original specifications. The Pratt & Whitney R-2800 engines were replaced by Wright Double Cyclones and plans to provide pressurization were abandoned, as well as a number of minor changes (like less cabin windows). Deliveries after the initial 25 were more adapted to the military role, like fitted with double cargo doors, a strengthened floor and hydraulically operated cargo handling winch. Forty folding seats took care of the seating in the C-46A.
The US entered the war on December 7th, 1941.
The C-46s and the C-47s were used on short and medium routes. The war effort required more orders and thus an order for 150 C-46As was placed for the USAAF and 120 C-46As for the US Navy in June 1942. Followed in October by another order for 200 more. Some examples were modified on the production line to C-46D standard. The next order was for a 1.000 aircraft and these were followed by a further 2.250 C-46s in late 1943 and 1944. But after V-E Day (May 7th, 1945) cancellations were put in effect.
The airlift from India to China, the socalled "Flying the Hump" operation, was the real hour of glory for the Curtiss C-46 Commando. In Feb. 1942 President Roosevelt ordered General Arnold to open a supply line across the Himalayas in support of General Chiang Kai-Shek (and his air adviser Claire L. Chennault) at a time when the Japanese offensive was at its peak. Rangoon fell in March 1942 and this cut off the supply via the Burma road. The initial 26 aircraft for this project were 10 ex-airline DC-3s and some C-53s. The flights were started in late 1942 by the China National Aviation Corporation (CNAC) and the USAAF. By December of that year some 62 DC-3s of various types were involved, but already 15 had been destroyed. Conditions were poor at the airfields serving the China airlift, in september 1942, e.g. fuel was still being pumped by hand from drums.
It was quite natural that the Chinese Air Force was to receive some C-46s and some 20 were left behind under Lend-Lease agreement. In fact, some C-46Es awaiting delivery in Tennessee, were picked up by Slick Airways and operated with the blue and white rudder striped with the Chinese Air Force markings.
One C-46 was delivered to the Russian Air Force. No production C-46s were supplied to the RAF, but the original CW-20 prototype was purchased by the USAAF and supplied to Britain in 1942; BOAC used it for 18 months or so, mainly for flights to Lisbon, but it was broken up in late 1943.
Records showed an abnormal number of explosions (31 between May 1943 and May 1945) in C-46s and this was attributed to the payload (gasoline drums, unpressurized cabin, high altitudes.. a leaky drum and a spark from the electrical system: a deadly combination). But after the war it was discovered that the unvented wing structure of the C-46 was the problem. Fuel leaking in the wing had nowhere to drain. A spark or static discharge led to the inevitable explosion. All C-46s certificated after the war were required to have a wing vent modification incorporated.
After the war, Curtiss proposed civilian developments of the C-46 and Eastern Air Lines ordered a number of CW-20Es late in 1945. The order was however cancelled and further C-46 developments were ceased by Curtiss.
The C-47 benefitted from its excellent reputation during the war, but also from the DC-3 pre-war days with the airlines. The surplus C-46s were picked up by entrepeneurs who sought to make money flying cargo on a non-scheduled basis. Capitol, Flying Tigers and World Airways were among them.
In many South American countries, surface transport is hindered by the nature of the terrain: Amazone jungle, the Andes, extensive swamplands. The C-46 became a common sight in countries like Bolivia, Peru, Brazil, Argentina and Chile. A workhorse like the C-46 could be put to good use there, mostly carrying cargo of all sorts.
The CIA was an avid user of the C-46. It played a role in many operations. Cuba and the "Bay of Pigs" fiasco was one. The CIA's "Liberation Air Force" for Cuba was stationed (clandestine) at "Happy Valley" in Nicaragua, consisting of five C-46s, as well as other types (C-54, B-26). In the process, Southern Air Transport was bought (consisting of only 1 C-46 at that time) in the early 1960s. The CIA had much use for aircraft in various roles and ended up owning its own airline: Civil Air Transport (CAT). A respectable airline opened many doors and provided a good cover. It was renamed Air America in 1959. And it even made money ! The holding company named Pacific Corporation, owned by the CIA, was stationed in Delaware. Many people involved did not know they worked, in a way, for the CIA, as it also operated as a normal commercial airline. By comparision, during the 1960s when Flying Tigers (at that time the largest US transport company) operated 28 planes and had 2.000 employees, and Air America had more than 150 planes and 8.000 employees ! Southern Air Transport played a similar role for the CIA and there were more. War surplus aircraft provided a good start, required little funding and the specifications fitted the covert operations like a glove. Quite a few pilots operating missions for the CIA, had their hands on the controls of a C-46 over the Himalayas. Air America used the C-46 in Vietnam, on routes between Saigon and Da Nang, but also during the last months of the Vietnam War with markings of the ICCS ("I Can't Control Shit") for the International Control Commission, to control the peace agreement. Quite a few C-46s disappeared without a trace while in use with the CIA.
The structural life of the C-46 was determined for some 50.000 hrs, but many did not get that far due to corrosion problems (particularly in the tail unit). The Hamilton engine replacements and overhauls have become expensive and time-consuming (the typical 1.450 hrs between overhaul on the R-2800 compare poorly with the 8.000 hrs and up on jet engines). The Hamilton 3-bladed props, installed to overcome the problems with the 4-bladed electrical Curtiss props, have become a rare commodity.
41-5159 through 41-5183, 41-5184 through 41-5204, 41-12280 through 41-12433, 41-24640 through 41-24775.
42-3564 through 42-3683, 42-60942 through 42-61091, 42-96529 through 42-96707 and many nonsequentially assigned serial numbers in the 42-96700 series, 42-96800 series, 42-101000 series, 42-101100 series, 42-101200 series, 42-107200 series, 42-107300 series.
43-46955 through 43-47304, 43-47315 through 43-47402, 43-46953 and 43-46954, 43-47305 through 43-47314, 43-43339 through 43-43340 (43-43341 through 43-43838 was cancelled).
44-77295 through 44-78544.
C-46A: Wright R-2800-51 (2000 horsepower), single cargodoors, strengthened floor, cargo door on port side, folding seats for 50 troops
TC-46A: At least 3 C-46As were converted to crew trainers (42-96605, 42-96756, 42-107320)
EC-46A: Given to Japanese Air Self Defense Force. C-46A modified for airways calibration.
XC-46A: C-46A 43-46956 was temporarily used for development tests. It was reverted back to C-46 status after completion of the tests.
XC-46B: C-46A 43-46963 was outfitted with a stepped windscreen and 2.100 horsepower R-2800-34W engines; see photo right.
XC-46C: Two C-46As fitted with Rocket Assisted Take Off (RATO) gear.
C-46D: Specialized troop carrier version of C-46 with a modified door (for paratroop dropping). More than 1.400 of this model Commando were purchased.
TC-46D: 15 C-46Ds were converted to crew trainers.
C-46E: 17 C-46Ds were modified with single cargo door, 3-bladed propellors, stepped windscreen and R-2800-75, 2.000 horsepower engines
C-46F: Same as C-46D, but powered with R-2800-75 engines (234 were bought)
C-46G: Same as C-46F, but with single cargo door and 2.100 horsepower R-2800-34 engines. Only 44-78945 was built in this configuration and it was eventually converted to XC-113, to test the Curtiss-Wright TG-100 (later T31-GE-3) gas turbine engine.
C-46H: More powerful version of C-46F, with twin tail wheels. 300 were ordered and later cancelled. One C-46A (42-107294) was modified to this standard after the war.
C-46J: Designation given to a planned, but never ordered, update to C-46E.
XC-46K: Projected as a conversion of C-46F, powered by R-3350-BD, 2.500 horsepower engines.
XC-46L: Reportedly 3 C-46As were modified with the 2.500 horsepower, R-3350-BD engines and used as flying testbeds.
ZC-46E: Created by redesignating the C-46E in 1946.
Cruising Speed: 236 mph (378 km/h)
Engines: 2 Pratt & Whitney R2800-34 Double Wasp radials Service Ceiling: 24.500 ft
Range: 3.150 miles (5.040 kms)
Physical characteristics: Wingspan: 108 ft (32,93 m)
Length: 76 ft, 4 in (23,26 m)
Height: 21 ft, 9 in (6,62 m)
Empty weight: 30.000 pounds (13.608 kgs)
Gross weight: 45.000 pounds (20.412 kgs)
Max. payload: 15.000 pounds (6.804 kgs) or 50 passengers
Credit:for the above information goes to:
Curtiss C-46 Commando , by John M.Davis, Harold G. Martin, John A. Whittle (published by Air-Britain)
Wings of the CIA , by Frederic Lert
The 'C'-Planes, US Cargo Aircraft 1925- to the Present , by Bill Holder & Scott Vadnais
And these links for more info on those brave people crossing the Himalayas:
Dirk Septer writes about 757 flights across the "Hump"
Official Home Page for the China National Aviation Corporation (CNAC)