The Curtiss C-46 Commando

The Curtiss C-46 Commando was a twin-engine cargolifter used primarily by the US Army Air Forces (USAAF) in World War II, although it saw action with other services during the war, and in later conflicts. The C-46 remains largely forgotten, since it was overshadowed by the much more famous Douglas C-47 Dakota transport. This document provides a history and description of the Commando.

Curtiss Commando Origins

The Curtiss Commando began life as a design for a 36-seat commercial airliner with a pressurized cabin, designated the "CW-20", with development initiated by Curtiss in 1936 under an engineering team led by chief designer George W. Page. The CW-20 was intended to provide a larger, more capable competitor to the Douglas DC-3, which was then entering service.

The CW-20 featured a roomy "double bubble" fuselage, with a cross-section in the form of two circle segments mated together, top and bottom. This configuration provided large internal volume and the structural strength to support pressurization. The junction between the small segment and the larger top segment was faired over to improve aerodynamics. The CW-20 also featured a low wing with twin radial engines, fully retractable taildragger landing gear, and a twin tailfins. The cockpit windscreen was flush with the fuselage contour, giving the aircraft a whale-like appearance.

The first "CW-20T" prototype was built at the Curtiss plant in Saint Louis, Missouri, and performed its initial flight on 26 March 1940, with Edmund T. "Eddie" Allen at the controls. Although Pratt & Whitney (P&W) R-2800 Double Wasp two-row air-cooled 18-cylinder radials were planned for the aircraft in production, the CW-20T was powered by two Wright R-2600 Cyclone engines with 1,194 kW (1,600 HP) each. Curtiss made a public announcement about their new airliner on 11 April 1940, giving it the name of "Substratosphere Transport", which was blessedly forgotten.

Flight tests quickly showed that the twin-fin tail left much to be desired, and it was replaced by a conventional tail arrangement with a single tailfin. The modified aircraft, now known as the "CW-20A", was demonstrated to airlines, and there were some interest in the type.

However, in September 1940 the US Army Air Corps (USAAC), implementing an increasingly frantic program to prepare for war, ordered 200 modified "CW-20Bs" with the military designation of "C-46". Production began at the Curtiss plant in Buffalo, New York, with the first "Commando" delivered to the US Army Air Forces (which had superseded the Air Corps in the meantime) on 12 July 1942. Many more would follow. With a war on, Curtiss focused on military production, and commercial production was out of the question for the duration.

Incidentally, the CW-20A prototype was pressed into service by the USAAF as the "C-55" on 20 June 1941. It only served with the military for three months, then being sold to the British Overseas Airway Corporation (BOAC), which operated it as the "Saint Louis". It was scrapped in October 1943.

The Curtiss C-46 Commando at war

The initial C-46 was an interim production type, rolled off the manufacturing line while Curtiss changed the design to fully meet USAAF specifications. The 26th aircraft delivered was the first full-specification "C-46A" or "CW-20B". Major changes in the C-46A relative to the CW-20A prototype included:

• Engine fit reverted to the planned Pratt & Whitney Double Wasp engines, with the R-2800-34 variant delivering 1,567 kW (2,100 HP) each, and driving four-bladed Curtiss electrically-operated propellers.
• The fairings between the top and bottom fuselage halves were deleted, as flight tests showed they provided no improvement in performance.
• Cabin pressurization was eliminated, the number of passenger windows was reduced, and 40 fold-down seats were fitted along the cabin walls.
• A cargo floor was installed, and a large cargo door was fitted on the left side of the rear fuselage. A passenger door was fitted into the cargo door.

In addition to 40 troops, loads for the C-46A included 33 stretchers with attendants, or 4,550 kilograms (10,000 pounds) of cargo. The Commando was the largest twin-engine aircraft operated by the USAAF, and it fact its wingspan was 1.2 meters (4 feet) longer than that of a Boeing B-17 Flying Fortress. The Commando's fully loaded weight was almost twice as much as C-47's.

The USAAF was enthusiastic about the Commando, and a total of 1,479 C-46s and C-46As were built by Curtiss in plants at Buffalo (1,039 "C-46A-CU" Commandos), Saint Louis (two "C-46A-CS" Commandos), and Louisville, Kentucky (438 "C-46A-CK" Commandos). They were flown by the US Army Air Transport Command, Air Service Command, and Troop Carrier Command. About 40 C-46As were passed on to the US Marine Corps with the designation "R5C-1", and some of these aircraft were later passed on to the US Naval Air Transport Command in turn.

Demand for the type was so great that the USAAF placed an order for 500 C-46A Commandos with Higgins Industries, famed for construction of landing craft and torpedo boats, but only two "C-46A-HI" Commandos were actually built by Higgins, being delivered in October 1944.

The Commando initially went into service on the South Atlantic ferry route, and would also participate as a glider tug in the Rhine crossings in March 1945. However, due to its long range, it was primarily used in the Pacific and China-Burma-India (CBI) theaters, becoming the primary cargolifter for ferrying supplies from India to China over "the Hump", the Himalaya Mountains, after the Japanese shut down the Burma Road in 1943. Commandos of Colonel Edward H. Alexander's "India-China Wing" of the USAAF Air Transport Command flew from primitive airstrips in the Indian state of Assam, climbing with overload cargoes to clear ridges from 3.7 to 4.3 kilometers (12,000 to 14,000 feet) high, to land at Chunking and drop off their loads for USAAF General Claire Chennault's 14th Air Force and Nationalist Chinese forces.

The loss rate of the C-46 was high and it had a mixed reputation with aircrews. Partly the problem was the fact that environment was very harsh, operating conditions were difficult, and Japanese fighters occasionally attacked the Commandos. During one attack, Captain Wally A. Gayda shoved a Browning Automatic Rifle out one of the forward cabin windows and shot down the attacker.

However, stories still circulate that the C-46 also suffered from a large number of engineering and manufacturing faults, in particular a leaky hydraulic system. Crews were said to take a barrel of hydraulic fluid along on flights to make sure that the hydraulic systems were topped off before they were used. There was also apparently a fuel leak problem that took a long time to work out, with aircraft being lost in midair explosions at a steady rate until it was.

It doesn't appear that the C-46 was an inherently bad aircraft, it was just rushed into service without the level of qualification that it would have been run through in peacetime, and it took a lot of work to get the bugs fixed. The aircraft's detractors called it the "Curtiss Calamity" and the "Leaky Tiki", though it was also more affectionately named "Dumbo", after the flying baby elephant in Walt Disney's 1941 animated movie.

Curtiss Commando Variants

There were a number of Commando variants, but only two were produced in numbers besides the C-46A:

• The only real difference of the "CW-20B-2" or "C-46D" from the C-46A was that the C-46D had double instead of single cargo doors. 1,410 of the variant were built by Curtiss at the Buffalo plant.
• The "CW-20B-4" or "C-46F" had a single door on both sides and squared-off wingtips, with 234 built by Curtiss at the Buffalo plant.

Minor variants included:

• The "CW-20B-1" or "XC-46B" was an experimental conversion of a Louisville-built C-46A that featured a "stepped" windscreen rather than the normal flush windscreen, giving the aircraft the look of a pregnant C-47 Dakota. It also featured P&W R-2800-34W engines with water injection for takeoff power boost.
• The "CW-20B-3" or "C-46E" featured R-2800-75 Double Wasps, the stepped windscreen of the XC-46B, and three-bladed Hamilton Standard propellers. While only 17 C-46Es were built, the three-bladed propeller was retrofitted to other Commando variants in the field, as it was more reliable than the Curtiss propeller, which had a nasty tendency to revert to fine pitch on its own.
• The single "CW-20B-5" or "C-46G" had the stepped windscreen and squared-off wingtips. It was later modified to evaluate the General Electric TG-100 turboprop, with the turboprop mounted in the right nacelle and the left nacelle retaining the P&W R-2800-34W radial engine. The modified C-46G was redesignated "XC-46C" and then "XC-113".
• Several variants were never completed. The "C-46H" was to have twin tailwheels; the "C-46J" was to be another stepped-windscreen variant; and the "XC-46K" was to be powered by Wright R-3350 radials. Three "XC-46L" conversions with the Wright radials were actually performed. In addition, late in the war Curtiss put together a mockup of an updated commercial version of the aircraft, the "CW-20E", but although there was airline interest, the type was never produced.

Pictures of Commandos show some of them fitted with a radio-compass loop antenna behind the cockpit, which would be a valuable piece of gear for Asian operations over long distances and in monsoon weather, but it is unclear if this was associated with a particular variant, with specific factory blocks, or was a field fit. Total Commando production came to 3,140 aircraft.

Curtiss Commando Postwar Service

Although large numbers of surplus Commandos were sold to civilian operators in the rapid military wind-down after World War II, the C-46 remained in US military service in good quantities well into the 1950s. Some were adapted as "TC-46D" trainers for the US Air Force (USAF), which the USAAF became in 1947.

The outbreak of the Korean War caught the US unprepared and scrambling for resources. C-46s were pulled out of mothballs or even bought back from commercial operators, and put into round-the-clock use with the USAF Combat Cargo Command hauling supplies from Japan to Korea, as well as participating in paratrooper drops. Commandos were still in US military service in the 1960s, and were used by the USAF 1st Air Commando Group for jungle supply drops and deliveries during the early part of the Vietnam War. The last Commandos were retired from USAF service in 1968.

Civilian Commandos were put to plenty of good use, generally as air freighters, though some were converted to an airliner configuration with proper passenger accommodations. Even as late as 1980, 300 or more Commandos were still operating.

Only a few dozen are still flying now. In the United States, two C-46Fs have been obtained by the Commemorative Air Force (CAF) and make appearances at airshows. One is painted silver with USAAF markings and is named "China Doll", though the CAF earlier flew it in Nationalist Chinese markings as "Humpty Dumpty". The other is painted camouflage green on top and light blue on the bottom and is named "Tinker Bell".

Footnote: The Curtiss C-76 Caravan

While the USAAF was awarding contracts to Curtiss to bring the C-46 Commando into operation, the service was hedging their bets by ordering a second transport from Curtiss, the "CW-27" or "C-76 Caravan". The Caravan was to be made as much as possible of wood in case supplies of light alloys dried up.

The USAAF placed an order for 11 "YC-76" pre-production aircraft in 1941, with the first performing its initial flight on 1 January 1943. The Caravan was smaller than the Commando and of different configuration, with a shoulder-mounted wing, a stepped-up cockpit, and retractable tricycle landing gear. It was powered by twin P&W R-1830-92 Twin Wasp radials with 895 kW (1,200 HP) each, and could carry 23 people, including the crew.

The evaluation was successful, and Curtiss went on to produce five "C-76" initial production aircraft, plus nine "YC-76A" modified service evaluation aircraft. These were delivered in 1943, but by that time there was no reason to think the Caravan would be needed, and large production orders with both Curtiss and Higgins Industries were cancelled.

Curtiss C-46 Commando - Comments

The C-46 remains a somewhat obscure aircraft, and information on it is both scarce and somewhat contradictory. Sources are particularly divided on its reputation, with many citing its lack of reliability. That wouldn't be too surprising given that Curtiss products were not exactly at the top of the class of American aircraft used in World War II.

However, the long service history seems to hint that the aircraft was regarded as both capable and satisfactory, at least after Curtiss hammered the worst bugs out, and one pilot who flew it during the Korean War, Lieutenant Spencer Grant, praised its reliability and capability highly, concluding: "In my opinion, the C-47 always got top billing, but the C-46 was twice the aircraft."

Author: Greg Goebel