Curtiss C-46 Commando

https://en.wikipedia.org/wiki/Curtiss_C-46_Commando

The Curtiss C-46 Commando is a transport aircraft derived from the Curtiss CW-20
pressurised high-altitude airliner design. Early press reports used the name
'Condor III' but the Commando name was in use by early 1942 in company
publicity. It was used as a military transport during World War II by the United
States Army Air Forces and also the U.S. Navy/Marine Corps, which used the
designation R5C. The C-46 served in a similar role to its Douglas-built
counterpart, the C-47 Skytrain, but it was not as extensively produced as the
latter.

After World War II, a few surplus C-46 aircraft were briefly used in their
originally designated role as passenger airliners, but the glut of surplus C-47s
dominated the marketplace and the C-46 was soon relegated to primarily cargo
duty. The type continued in U. S. Air Force service in a secondary role until
1968. The C-46 continues in operation as a rugged cargo transport for Arctic and
remote locations with its service life extended into the 21st century.

The prototype for what would become the C-46, the Curtiss CW-20, was designed in
1937 by George A. Page Jr., the chief aircraft designer at Curtiss-Wright. The
CW-20 was a private venture intended to compete with the four-engined Douglas
DC-4 and Boeing Stratoliner by the introduction of a new standard in pressurized
airliners. The CW-20 had a patented fuselage conventionally referred to as a
"figure-eight" (or "double-bubble") which enabled it to better withstand the
pressure differential at high altitudes. This was done by having the sides of
the fuselage creased at the level of the floor that not only separated the two
portions but shared in the stress of each, rather than just supporting itself.
The main spar of the wing could pass through the bottom section which was mainly
intended for cargo without intruding on the passenger upper compartment. A
decision to utilize a twin-engine design instead of a four-engine configuration
was considered viable if sufficiently powerful engines were available, allowing
for lower operating costs and a less complex structure.

Engineering work involved a three-year commitment from the company and
incorporated an extensive amount of wind tunnel testing at the California
Institute of Technology (Caltech). The resultant design was a large but
aerodynamically "sleek" airliner, incorporating the cockpit in a streamlined
glazed "dome". The engines featured a unique nacelle tunnel cowl where air was
ducted in and expelled through the bottom of the cowl, reducing turbulent
airflow and induced drag across the upper wing surface. After a mockup was
constructed in 1938, Curtiss-Wright exhibited the innovative project as a
display in the 1939 New York World's Fair.

A total of 200 C-46As in two initial batches were ordered in 1940, although only
two were actually delivered by December 7, 1941. At this time, one other
important change was made; more powerful 2,000 hp Pratt & Whitney R-2800 Double
Wasp engines replaced the two Wright Twin Cyclones. By November 1943, 721
modifications had been made to production models, although many were minor, such
as fuel system changes and fewer cabin windows were also adopted. Subsequent
military contracts for the C-46A extended the production run to 1,454 examples,
40 of which were destined for the U.S. Marine Corps, to be designated R5C-1. The
military model was fitted with double cargo doors, a strengthened floor and a
hydraulically operated cargo handling winch; 40 folding seats were the sole
passenger accommodation for what was essentially a cargo hauler. Tests indicated
that the production C-46 was capable of carrying a substantial payload, and it
could fly well on one engine. When empty, the aircraft could even climb on one
engine at 200–300 ft per minute.

The final large production-run C-46D arrived in 1944–45, and featured single
doors to facilitate paratroop drops; production totaled 1,430 aircraft. Although
a one-off XC-46B experimented with a stepped windscreen and uprated powerplants,
a small run of 17 C-46Es had many of the same features as the XC-46B along with
three-bladed Hamilton-Standard propellers replacing the standard
Curtiss-Electric four-bladed units. A last contract for 234 C-46Fs reverted to
the earlier cockpit shape but introduced square wingtips. A sole C-46G had the
stepped windscreen and square wingtips but the end of the war resulted in the
cancellation of any additional orders for the type.


Role
Military transport aircraft

National origin
United States

Manufacturer
Curtiss-Wright

First flight
26 March 1940

Introduction
1941

Status
Active in limited civilian use

Primary users
United States Army Air Forces
United States Air Force
United States Marine Corps
United States Navy

Produced
1940–1945

Number built
3,181

Pacific Theater

Most famous for its operations in the China-Burma-India theater (CBI) and the
Far East, the Commando was a workhorse in flying over "The Hump" (as the
Himalaya Mountains were nicknamed by Allied airmen), transporting desperately
needed supplies to troops in China from bases in India. A variety of transports
had been employed in the campaign, but only the C-46 was able to handle the wide
range of adverse conditions encountered by the USAAF. Unpredictably violent
weather, heavy cargo loads, high mountain terrain, and poorly equipped and
frequently flooded airfields proved a considerable challenge to the transport
aircraft then in service, along with a host of engineering and maintenance
nightmares due to a shortage of trained air and ground personnel.

Europe

Although not built in the same quantities as its more famous wartime compatriot,
the C-47 Skytrain, the C-46 nevertheless played a significant role in wartime
operations, although the aircraft was not deployed in numbers to the European
theater until March 1945. It augmented USAAF Troop Carrier Command in time to
drop paratroopers in an offensive to cross the Rhine River in Germany (Operation
Varsity).

Despite its obvious and valuable utility, the C-46 remained a maintenance
nightmare throughout its AAF career. The official history of the Army Air Forces
summarized its shortcomings:

"But from first to last, the Commando remained a headache. It could be kept
flying only at the cost of thousands of extra man-hours for maintenance and
modification. Although Curtiss-Wright reported the accumulation by November 1943
of the astounding total of 721 required changes in production models, the plane
continued to be what maintenance crews around the world aptly described as a
"plumber's nightmare." Worse still, the plane was a killer. In the experienced
hands of Eastern Air Lines and along a route that provided more favorable flying
conditions than were confronted by military crews in Africa and on the Hump
route into China, the plane did well enough. Indeed, Eastern Air Lines lost only
one C-46 in more than two years of operation. But among the ATC pilots the
Commando was known, with good reason, as the "flying coffin." From May 1943 to
March 1945, Air Transport Command received reports of thirty-one instances in
which C-46s caught fire or exploded in the air. Still others were listed merely
as "missing in flight," and it is a safe assumption that many of these exploded,
went down in flames, or crashed as the result of vapor lock, carburetor icing,
or other defects.

Postwar

Overall, the C-46 had been successful in its primary role as a wartime cargo
transport, and had benefited from a series of improvements. Like the C-47/DC-3,
the C-46 seemed destined for a useful career as a postwar civilian passenger
airliner, and was considered for that purpose by Eastern Airlines. However, the
high operating costs of the C-46 (up to 50% greater than the C-47), soon caused
most operators to change their minds. Consequently, most postwar C-46 operations
were limited to commercial cargo transport, and then only for certain routes.
One of the C-46's major drawbacks was the prodigious fuel consumption of its
powerful 2,000 hp engines, which used fuel at a much higher rate than the
C-47/DC-3. Maintenance was also more intensive and costlier. Despite these
disadvantages, surplus C-46s were used by some air carriers, including Capitol,
Flying Tigers, Civil Air Transport (CAT) and World Airways to both carry cargo
and passengers. Many other small carriers also eventually operated the type on
both scheduled and non-scheduled routes. The C-46 became a common sight in South
America, and was widely used in Bolivia, Peru, Brazil, Argentina and Chile,
especially in mountainous areas (where a good climb rate and high service
ceiling were required) or to overfly deep jungle terrain where ground transport
was impracticable.

Specifications (C-46A)

General characteristics
Crew: 4
Capacity:
40 troops or
30 stretcher patients or
15,000 lb (6,800 kg) cargo

Length: 76 ft 4 in (23.27 m)
Wingspan: 108 ft 0 in (32.91 m)
Height: 21 ft 9 in (6.62 m)
Wing area: 1,360 ft2 (126.3 m2)
Empty weight: 30,669 lb (14,700 kg)
Max. takeoff weight: 45,000 lb (20,412 kg)
Powerplant: 2 × Pratt & Whitney R-2800-51 two-row 18-cylinder radial engines,
2,000 hp (1,492 kW) each

Performance
Maximum speed: 270 mph (235 knots, 435 km/h) at 15,000 ft (4,600 m)
Cruise speed: 173 mph (150 knots, 278 km/h)
Range: 3,150 mi (2,739 nmi, 5,069 km at 173 mph (278 km/h))
Service ceiling: 24,500 ft (7,468 m)
Rate of climb: 1,175 ft/min (6.0 m/s)




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