The introduction of the all-metal twin-engined monoplane in the 1930's, e.g., the Boeing 247 and the Douglas DC-1, DC-2 and DC-3, permitted U.S. commercial airlines to make a profit by transporting people in addition to airmail. [In U.S. Navy (USN) service, the DC-2 was designated R2D, q.v., and the DC-3 was designated R4D, q.v.] In 1935, the Aeroplane Division of the Curtiss-Wright Corporation in Buffalo, New York, began design studies for a new transport, designated Model CW-20, intended to compete with the DC-3. The design was finalized in 1936 and when compared to the DC-3, (1) it had 40 percent more passenger capacity allowing 24- to 34-seats or 20-berths, (2) was to be pressurized giving it the ability to fly above the weather, (3) had an area beneath the cabin floor to carry baggage or cargo, a novel feature at the time, (4) more powerful engines and (5) a greater fuel capacity.
A unique feature of the CW-20 was the design of the fuselage. Since the aircraft was to be pressurized, the fuselage had to be circular to provide structural strength but a fuselage that was a complete circle would have increased the frontal area resulting in increased drag. Curtiss-Wright solved this problem by designing a fuselage that consisted of two circular segments intersecting at a common point; from the front, it looked like an inverted number 8. The point where the two segments met was the cablin floor and this is what allowed the cargo area beneath the floor. The nose of the aircraft was well streamlined; this was accomplished by aligning the cockpit windows with the fuselage contours instead of using a stepped windshield design of the DC-3 and other contemporary aircraft.
The original prototype was designated Model CW-20T because of its two fins and rudders. This aircraft was an all metal twin-engined low-wing monoplane with a retractable landing gear; the main landing gear retracted into the engine nacelles and the tail wheel retracted into the fuselage. The ailerons were metal framed and covered with fabric. Although the production models were to be pressurized, this equipment was not fitted on the prototype. At the time it made its first flight on 26 March 1940, the CW-20T was the largest twin-engined transport in the world. During testing, the two fins and rudders were replaced by a single unit and the aircraft was again redesignated the CW-20. The prototype was purchased by the U.S. Army Air Forces (USAAF) in June 1941 and designated C-55-CS. In September 1941, it was returned to Curtiss and sold to British Overseas Airways Corporation (BOAC), registered G-AGDI, and converted to a 24-seat transport. The CW-20 was flown to Prestwick, Scotland in November 1941 and began flying long haul routes and the route from Gibraltar to Malta until being scrapped in October 1943.
When the U.S. military buildup began in 1940, the U.S. Army Air Corps (USAAC), which was superseded by the USAAF on 20 June 1941, began purchasing transport aircraft in large numbers. On 13 September 1940, the USAAC ordered 46 CW-20As designated C-46-CU; the last 21 were delivered as Model CW-20Bs, designated C-46A-1-CU, described below. None of the C-46's purchased by the U.S. military were pressurized. The CW-20A/C-46-CUs were designed as troop transports for 50 troops, or 33 litter patients and four attendants, but they could also carry up to 10,000 pounds (4,536 kg) of cargo. A crew of four, pilot, co-pilot, navigator and radio operator, could be accommodated.
The CW-20B/C-46A was the first militarized version of this aircraft. The C-46A had a reinforced floor to accommodate 15,000 pounds (6,804 kg) of cargo; a large two-segment cargo door on the port side aft of the wing opening outward and upward that measured 78.5 inches (199.4 cm) high forward, 66.5 inches (168.9 cm) aft and 95.5 (252.7 cm) inches wide; and 2,000 hp (1,491 kW) Pratt & Whitney R-2800-51 18-cylinder, twin-row, air-cooled, radial engines driving Curtiss Electric four-bladed constant-speed full-feathering propellers. A total of 1,481 C-46As were built; Curtiss built 1,039 C-46A-CUs at their Buffalo, New York plant; 438 C-46A-CKs at their plant in Louisville, Kentucky; and two C-46A-CS s at the St. Louis, Missouri plant; and Higgins Aircraft Inc. built two C-46A-HIs at their New Orleans, Louisiana plant.
The C-46As experienced three main problems: (1) the Curtiss propeller had a habit of moving into fine pitch because of corrosion, (2) vapor lock of the engines at high altitude when switching fuel tanks, and (3) the hydraulic system was very complex and required considerable maintenance.
Another 1,662 Commandos were delivered to the USAAF as the C-46D, C-46E, C-46F and C-46G.
R5C-1: A total of 160 C-46As delivered to the USMC starting in February 1943. This included 92 C-46A-CUs and 68 C-46A-CKs of various blocks.
R5C-1T: At least one USN aircraft converted for training at Naval Air Station (NAS) Memphis, Tennessee ca. 1954.
R5C-1Z: At least one USMC aircraft converted to a VIP transport in 1946.
All 160 R5C-1's ordered by the USN were delivered to the USMC; the first aircraft was delivered on 25 February 1943 but deliveries were slow and by December 1943, only 30 Commandos had been received. The first two squadrons were equipped with R5C-1's in August 1944 and by the end of the war, six squadrons were flying these aircraft, i.e.:
- Marine Transport Squadron Two Hundred Fifty Two (VMR-252) had been in existence since the 1920's under various designations and had moved to Marine Corps Air Station (MCAS) Ewa, Oahu, Territory of Hawaii in 1941. Equipped with R5C-1's in August 1944, the squadron flew supply and evacuation missions in support of the invasions of the Marshall Islands; Saipan (15-10N 145-45E), Tinian (15-00N 145-38E) and Guam (13-28N 144-47E) Islands in the Mariana Islands; and Iwo Jima in the Volcano Islands (24-47N 144-20E). The squadron moved to Kwajalein Island, Kwajalein Atoll, Marshall Islands (9-05N 167-20E) in March 1945 and began supporting the campaign on Okinawa in the Ryukyu Islands (26-30N 128-00E).
- VMR-952 moved to MCAS Ewa in February 1944 and after being equipped with R5C-1's in August 1944, moved to Emirau Island, St. Matthias Group, Bismarck Archipelago (1-40S 150-00E) at the end of the month to support the invasion of Peleliu Island, Palau Islands (7-01N 134-15E) by escorting tactical aircraft and evacuating wounded. By November 1944, the squadron's area of operations included Tarawa Atoll in the Gilbert Islands (1-25N 173-00E); Ulithi Atoll, Caroline Islands (9-58N 139-40E); and Saipan, Tinian and Guam Islands in the Mariana Islands. VMR-952 transferred to Guam in December 1944 and began supply and medical evacuation missions which continued until the end of the war.
- In August 1944, VMR-953 arrived at MCAS Ewa from the U.S. and was equipped with R5C-1's. The squadron began flying missions from Ewa to various Pacific locations including Leyte Island in the Philippine Islands and Okinawa in the Ryukyu Islands until VJ Day.
- In February 1945, VMR-353 at Saipan began equipping with R5Cs. The squadron flew wounded from Iwo Jima and later Okinawa until the end of the war.
- The forward echelon of VMR-352 moved to MCAS Ewa from the U.S. in February 1945 and began operating these aircraft throughout the Pacific. The remainder of the squadron moved to Hawaii in July 1945.
- The last squadron to operate the R5C was VMR-253 on Guam. They began equipping with the Commando in March 1945 and used the aircraft in supply and evacuation missions until the end of the war.
After World War II, the USMC
operated these aircraft for several years and a few USN support squadrons
were also equipped with the R5C. Ten R5C-1's were delivered to the U.S.
Coast Guard (USCG) and based at Coast Guard Air Station (CGAS) Elizabeth
City, North Carolina to support the Coast Guards Aircraft Repair and Supply
Center. These aircraft were used for logistic and personnel transportation
to Coast Guard facilities in the U.S. and overseas. The last USCG R5C-1
was struck from the inventory in 1950.
Wing Span: 108 feet 1 inch
Length: 76 feet 4 inches (23.27 meters)
Height: 21 feet 9 inches (6.63 meters)
Wing Area: 1,360 square feet (126.35 square meters)
Empty Weight: 30,241 pounds (13,717 kg)
Gross Weight: 46,000 pounds (20,865 kg)
Fuel Capacity: 1,400 U.S. gallons (5,300 liters) plus 1,600 U.S. gallons (6,057 liters) in cabin tanks
Maximum Speed: 230 mph at 16,000 feet (370.1 km/h at 4,877 meters)
Cruising Speed: 173 mph (278.4 km/h)
Rate of climb: 830 feet (253 meters) per minute
Service Ceiling: 24,500 feet (7,468 meters)
Combat Radius: 1,960 miles at 121 mph at 1,500 feet (3,154 km at 194.7 km/h at 457.2 meters)
Maximum cruising range: 3,150 miles at 173 mph (5,069 km at 278.4 km/h)