Curtiss C-46 Commando
The Curtiss C-46 Commando was a twin-engine heavy-lift transport aircraft developed by the Curtiss-Wright Corporation for the United States Army Air Forces during World War II.[1] Originally conceived in 1936 as the CW-20, a 36-passenger pressurized commercial airliner to compete with the Douglas DC-4, the design was militarized in response to wartime needs, featuring a distinctive double-lobe fuselage cross-section that allowed a reinforced cargo floor to span between the engines for efficient loading of troops or supplies.[2] The prototype first flew on March 26, 1940, and the production C-46 entered service in 1942 as the largest and heaviest twin-engine aircraft operated by the U.S. military at the time, capable of carrying up to 50 troops, 33 litter patients, or approximately 15,000 pounds of cargo.[3] Over 3,181 units were built between 1942 and 1947, primarily at Curtiss-Wright's Buffalo, New York, factory, making it one of the most produced U.S. transport aircraft of the era.[4] Development of the C-46 accelerated amid the U.S. entry into World War II, with initial military orders placed in 1940 for the XC-46 prototype, which incorporated modifications like large clamshell cargo doors, a strengthened structure, and folding seats to meet transport requirements.[5] Despite early challenges, including engine reliability issues with the Pratt & Whitney R-2800 Double Wasp radials and production delays due to the aircraft's complexity, the C-46 proved invaluable for long-range operations, particularly in high-altitude environments where its powerful engines and robust design excelled.[6] Key variants included the C-46A with improved cargo handling and the C-46D/F models featuring unpressurized cabins and enhanced cold-weather performance for specific theaters.[7] In terms of specifications, the C-46 had a wingspan of 108 feet, a length of 76 feet 4 inches, and a height of 21 feet 9 inches, powered by two 18-cylinder air-cooled Pratt & Whitney R-2800-51 engines each producing 2,000 horsepower.[4] It achieved a maximum speed of 270 miles per hour, a cruising speed of 150 knots (173 mph), and a range of up to 1,200 miles with a full payload, with an empty weight of about 31,000 pounds and a maximum takeoff weight of 48,000 pounds in military configuration.[7] The aircraft's four-person crew typically included a pilot, copilot, navigator, and radio operator, and it featured advanced features for its time, such as conventional tailwheel landing gear and provisions for defensive armament like .50-caliber machine guns in some variants.[8] Operationally, the C-46 played a pivotal role in World War II, most famously ferrying supplies over "The Hump"—the treacherous Himalayan route from India to China—where it delivered critical cargo to Allied forces fighting Japanese occupation, logging millions of ton-miles despite harsh weather and mechanical risks.[7] Post-war, surplus C-46s served in the Korean War for troop and supply transport, and some were used by the U.S. Air Force and continue to be used by civilian operators in remote cargo roles as of 2025, including in rescue missions and firefighting, underscoring its enduring versatility as a rugged workhorse aircraft.[2][9]Design and development
Origins and requirements
In the mid-1930s, the U.S. Army Air Corps sought a modern twin-engine transport aircraft to replace its aging fleet of Douglas C-33 and C-34 cargo planes, which were conversions of the DC-2 airliner and increasingly inadequate for emerging long-range needs.[7] In 1937, the Army issued a specification for a new transport capable of carrying a 20,000-pound payload over 4,000 miles while operating above 25,000 feet to evade weather and enemy defenses, though no manufacturer could fully meet these demanding requirements at the time.[1] Curtiss-Wright responded by initiating development of the CW-20 in 1937 as a pressurized civilian airliner aimed at high-altitude routes, drawing initial design influences from the company's earlier Curtiss AT-32 twin-engine transport and the pioneering pressurized cabin of Lockheed's XC-35.[1] Trans World Airlines (TWA) expressed early interest in the CW-20 for its potential to enable faster, weather-avoiding transcontinental flights, viewing it as a "super-DC-3" with capacity for 36 passengers at altitudes over 20,000 feet.[1] However, TWA ultimately selected the Boeing 307 Stratoliner, leaving Curtiss-Wright to pivot toward military applications as tensions escalated in Europe.[1] The CW-20 prototype, designated CW-20T for its transport configuration, incorporated a distinctive double-lobe fuselage to accommodate pressurization and maximize cargo volume, aligning closely with the Army's 1937 needs despite the civilian origins.[7] In September 1940, the Army Air Corps ordered 46 C-46 variants to evaluate and initiate production of its potential as a military transport, marking the transition from commercial concept to the C-46 Commando.[4][10] This contract emphasized the aircraft's ability to handle heavy payloads at high altitudes, setting the stage for rapid production amid World War II demands.[7]Design evolution
The Curtiss-Wright CW-20 project originated in 1937 as a private venture to develop a pressurized, high-altitude civilian airliner capable of carrying 34 passengers, designed by chief engineer George A. Page Jr. to compete with emerging transcontinental routes.[11][12] Between 1938 and 1939, extensive wind tunnel testing of scale models was performed at the Guggenheim Aeronautical Laboratories at the California Institute of Technology, optimizing the low-wing configuration for aerodynamic efficiency and resulting in a notably sleek nose section and an enlarged, circular fuselage cross-section to accommodate up to 40-50 passengers or equivalent cargo volume while supporting pressurization.[6][13] The CW-20T prototype, constructed with a strengthened fuselage for potential cabin pressurization, completed its maiden flight on March 26, 1940, from Buffalo, New York, powered by two 1,700 horsepower Wright R-2600 Twin Cyclone radial engines.[11][13] As World War II escalated, the U.S. Army Air Forces evaluated the prototype—redesignated XC-55 in 1941—for military transport potential, prompting its conversion to the C-46 designation under a contract for initial production models.[14][1] Key modifications for military adaptation included replacing the original engines with more powerful twin Pratt & Whitney R-2800-51 Double Wasp radials, each rated at 2,000 horsepower, to enhance high-altitude performance over mountainous terrain.[13][4] The planned pressurization system, intended to maintain a 10,000-foot cabin altitude at 25,000 feet, encountered significant reliability challenges during ground testing and early flight trials, including leaks and control complexities, leading to its abandonment in favor of unpressurized designs to accelerate wartime production.[6][8] To facilitate cargo operations, the civilian airliner layout evolved with the addition of large side cargo doors, reinforced flooring capable of supporting heavy loads, and provisions for rapid reconfiguration between passenger and freight roles in the C-46A variant.[4][15]Production history
Production of the Curtiss C-46 Commando began at Curtiss-Wright's primary facility in Buffalo, New York, with the first aircraft rolling out in May 1942 and delivery to the U.S. Army Air Forces occurring on July 12, 1942.[5] Initial output was modest as the company ramped up from the CW-20 prototype design, but by late 1944, the Buffalo plant achieved a peak production rate of 200 aircraft per month to meet urgent wartime demands. Manufacturing expanded to additional Curtiss-operated sites, including St. Louis, Missouri, and a government-owned plant in Louisville, Kentucky, while Higgins Industries in New Orleans handled subcontracting for components like wing panels, assembling a small number of complete airframes.[1] A total of 3,181 C-46s were ultimately produced across all variants and facilities before the program concluded, with the majority built during World War II to support transport operations.[4] Wartime production faced significant hurdles, including material shortages that affected aluminum and other strategic resources essential for airframe construction, as well as supply chain disruptions common to the broader U.S. aircraft industry.[16] Labor issues compounded these problems, with strikes at Curtiss-Wright plants—such as a welders' walkout in St. Louis in September 1943 and a broader dispute resolved in December 1943—halting assembly lines and delaying deliveries.[17][18] Production C-46s were powered by Pratt & Whitney R-2800 Double Wasp radials (2,000 hp each), a change from the prototype's Wright R-2600 Twin Cyclones (1,700 hp), to improve high-altitude performance. High demand for the R-2800 in other aircraft like the P-47 Thunderbolt contributed to production challenges.[6] Following Japan's surrender in August 1945, production halted abruptly that year, with remaining contracts fulfilled through minimal postwar orders for specialized variants.[12] The resulting surplus of military C-46s facilitated conversions for civilian applications, including passenger and cargo configurations operated by airlines such as Eastern Air Lines and Flying Tigers, extending the type's service life into the commercial sector.[19]Technical description
Airframe and structure
The Curtiss C-46 Commando's fuselage was constructed as an all-metal semi-monocoque structure using aluminum alloys, consisting of four main sections joined by bulkheads and longerons for enhanced rigidity and load distribution.[20][21] This design incorporated a distinctive "double-bubble" or figure-eight cross-section, where the upper lobe accommodated passengers or cargo and the lower provided additional volume for freight, with the cabin floor serving as a common pressure bulkhead in the original pressurized concept. Although production military variants were typically unpressurized to reduce weight and complexity, the airframe retained structural capability for cabin pressurization.[8] The wings featured a high-aspect-ratio configuration optimized for efficient long-range transport, with a span of 108 feet (32.92 meters) and a total area of 1,360 square feet (126 square meters).[3] They utilized NACA 23017 airfoil sections at the root transitioning to NACA 4410.5 at the tips, supported by a three-spar center section integrated with the fuselage for load sharing. The wing design included provisions for internal cargo storage, allowing for flexible loading of pallets and equipment without external protrusions.[21] Key structural features for cargo handling included reinforced flooring capable of supporting a 15,000-pound payload, distributed across the main deck with tie-down points for securing loads.[12] Access was provided via large clamshell cargo doors measuring approximately 9 feet by 6 feet on the port side, facilitating rapid loading and unloading of bulky items such as jeeps or supplies.[22] The aircraft employed a tricycle landing gear arrangement with twin wheels on each main strut and a single nose wheel, retracting inward into the fuselage and engine nacelles for a streamlined profile.[7] Overall dimensions comprised a length of 76 feet 4 inches (23.27 meters), height of 21 feet 9 inches (6.63 meters), emphasizing the C-46's role as a robust heavy-lift transport.[3] The airframe's integration with twin radial engines required reinforced nacelle mounts to handle vibrational and thrust loads.[21]Engines and systems
The Curtiss C-46 Commando was powered by two Pratt & Whitney R-2800 radial engines, each delivering 2,000 horsepower.[7] These 18-cylinder, air-cooled Double Wasp engines, typically the R-2800-51 variant in later models, drove three-bladed Hamilton Standard propellers in early models and four-bladed Curtiss Electric propellers in later production, with a diameter of approximately 15 feet, providing reliable thrust for heavy-lift operations despite the aircraft's high fuel consumption.[4][23][5] Although designed with a cabin pressurization system derived from the original CW-20 airliner concept, most wartime C-46 production models omitted full pressurization due to manufacturing priorities, relying instead on oxygen masks for crew and passengers at high altitudes.[6] Where implemented, the system utilized engine-driven compressors to maintain cabin pressure.[4] The aircraft featured pneumatic de-icing boots on the leading edges of the wings, tail surfaces, and propellers, inflated by engine bleed air to break away accumulated ice during flight in adverse weather.[24] Fuel was stored in wing tanks with a total capacity of 2,780 US gallons, distributed across multiple cells for balanced weight distribution and long-range missions, supplemented by optional fuselage tanks for extended operations.[24] The electrical system employed 28V DC generators driven by the engines, powering essential avionics, lighting, and accessories through a bus configuration that included battery backup for engine starts and emergency operations.[6] Hydraulic systems, operating at pressures of 1,050 to 1,350 psi in the main circuit and 750 to 1,050 psi in the auxiliary, actuated the landing gear, wing flaps (extendable to 35 degrees), brakes, and cowl flaps via engine-driven pumps and reservoirs.[24] For navigation and communication, the C-46 incorporated basic radio sets including VHF communication and navigation receivers, often supplemented by an autopilot for heading and altitude hold during long-haul flights.[6] High-altitude oxygen systems provided individual masks and regulators for the crew and up to 40 passengers, critical for over-the-Hump routes exceeding 15,000 feet where thin air posed physiological risks.[24]Performance characteristics
The Curtiss C-46 Commando demonstrated robust performance for its era as a twin-engine transport, powered by two Pratt & Whitney R-2800 radial engines each producing up to 2,000 horsepower, enabling it to outperform contemporaries like the Douglas C-47 in high-altitude operations.[25] Its maximum speed reached 270 mph at 15,000 feet, while the typical cruise speed was approximately 200 mph, allowing efficient long-distance hauling under load.[25] The service ceiling stood at 27,600 feet, with a rate of climb of 1,040 feet per minute, facilitating operations over challenging terrain such as the Himalayan "Hump" routes.[25] Key operational metrics included a range of 1,200 miles when carrying a full payload of around 15,000 pounds, though ferry range extended to nearly 3,000 miles with minimal load and maximum fuel.[25][26] Takeoff performance required approximately 2,950 feet for ground roll under standard conditions, with the aircraft's empty weight at 32,579 pounds and maximum takeoff weight up to 49,300 pounds.[27][25] Stall speed was around 80 mph indicated airspeed under typical loaded conditions, emphasizing the need for precise speed management during approach.[28] In terms of handling, the C-46 exhibited stability in turbulent conditions owing to its deep, pressurized fuselage design, which contributed to a smooth ride at altitude.[26] However, it was prone to Dutch roll oscillations without a yaw damper, a characteristic addressed in later modifications through control surface enhancements like feel-tabs on the elevator and rudder.[29] This instability at low speeds and during ground operations demanded skilled piloting, particularly in crosswinds or asymmetric power scenarios.[30]| Performance Parameter | Value |
|---|---|
| Maximum Speed | 270 mph at 15,000 ft[25] |
| Cruise Speed | 200 mph[25] |
| Service Ceiling | 27,600 ft[25] |
| Rate of Climb | 1,040 ft/min[25] |
| Range (with payload) | 1,200 miles[25] |
| Ferry Range | ~3,000 miles[26] |
| Empty Weight | 32,579 lb[25] |
| Max Takeoff Weight | 49,300 lb[25] |
| Stall Speed (approx.) | 80 mph IAS[28] |
Variants
Military variants
The military variants of the Curtiss C-46 Commando were primarily developed for the United States Army Air Forces (USAAF) as a twin-engine heavy transport capable of carrying troops, cargo, or medical evacuations over long distances and challenging terrain. Derived from the CW-20 airliner design, these variants featured Pratt & Whitney R-2800 Double Wasp radial engines, a low-wing configuration, and a distinctive double-bubble fuselage for increased cargo volume. Key adaptations included reinforced floors for heavy loads, large access doors, and high-altitude modifications to address early pressurization and icing issues encountered in operations. The XC-46 served as the prototype for military evaluation, powered by two 2,000 hp R-2800-4 engines; it underwent testing to validate the design for troop and cargo transport roles before production began. The C-46A was the first major production model, introduced in March 1943, with R-2800-51 engines rated at 2,000 hp each, a large cargo door on the left side of the fuselage, a strengthened floor, and provisions for 40 folding troop seats or 33 litters with attendants; it could carry up to 10,000 pounds of cargo and had a crew of four (pilot, co-pilot, engineer, radio operator). A total of 1,490 C-46As were built, including 160 for the US Navy and Marine Corps as R5C-1, making it a cornerstone of USAAF logistics.[31] The C-46D, entering service in April 1944, incorporated carburetor anti-icing, carburetor heating, cabin heaters, and a single cargo door optimized for high-altitude performance; equipped with carbureted R-2800-51 engines, it was specifically tailored for "Hump" operations over the Himalayas, with 1,410 units produced.[31] Later models addressed ongoing improvements in reliability and load-handling. The C-46E featured a stepped windscreen for better visibility, more powerful R-2800-75 engines (2,000 hp), cabin heating enhancements, and strengthened floors; 17 were built in 1945. The C-46F added a rounded nose and dual cargo doors for easier loading, retaining R-2800-51 engines, with 234 produced in late 1945 to support postwar logistics. The C-46G was similar to the F but with a single cargo door and upgraded R-2800-34 engines (2,100 hp); just one example (44-78945) was completed, later converted for engine testing as the XC-113 turboprop testbed.[32] For naval service, the R5C-1 was the US Navy and Marine Corps designation for a C-46A adaptation, featuring the same R-2800-51 engines and a gross weight of 45,000 pounds, capable of transporting 40 troops or 33 litters; 160 were built and delivered between 1943 and 1944, with three additional C-46F evaluations as R5C-2 in 1945, emphasizing its role as a heavy hauler superior to the C-47 in range and capacity. Three R5C-1s were evaluated as R5C-2. Postwar, some C-46s were redesignated UC-46 for utility transport duties in the US Air Force, involving minor modifications for general support roles such as paratroop drops and cargo hauling. Limited adaptations included trainer configurations designated TC-46, with at least 13 conversions for crew training.[32] Across variants, engine choices focused on double-row radials for reliability, with cargo configurations varying from side-loading doors to tropical kits for equatorial operations, enabling the Commando to haul up to 15,000 pounds in optimized setups.| Variant | Engines | Key Modifications | Number Built | Primary Role |
|---|---|---|---|---|
| XC-46 | 2 × R-2800-4 (2,000 hp) | Prototype testing; basic military configuration | 1 | Evaluation |
| C-46A | 2 × R-2800-51 (2,000 hp) | Large side cargo door, reinforced floor, 40 seats | 1,490 | Troop/cargo transport |
| C-46D | 2 × R-2800-51 (carbureted, 2,000 hp) | Anti-icing, cabin heat, single door | 1,410 | High-altitude supply (Hump) |
| C-46E | 2 × R-2800-75 (2,000 hp) | Stepped windscreen, strengthened floors, improved heating | 17 | Enhanced transport |
| C-46F | 2 × R-2800-51 (2,000 hp) | Dual cargo doors, rounded nose | 234 | Late-war logistics |
| C-46G | 2 × R-2800-34 (2,100 hp) | Single door variant of F | 1 | Testbed precursor (XC-113) |
| R5C-1 | 2 × R-2800-51 (2,000 hp) | Naval adaptation of C-46A, retractable gear into nacelles | 160 | Marine/Navy transport |
| UC-46 | Varied (R-2800 series) | Utility conversions for postwar USAF | Unspecified conversions | General utility |
| TC-46 | Varied (R-2800 series) | Trainer conversions | At least 13 | Crew training |