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| Top: Douglas C-74 Globemaster (serial number 42-65404) Bottom: C-74 Globemaster (serial number 42-65402) in flight |
When the US entered World War II after the Japanese attack on Pearl Harbor in December 1941, the US Army Air Force, sensing grievous losses of Allied merchant ships to U-boats and Focke-Wulf Fw 200 patrol bombers, but also facing the arduous task of capturing Japanese-controlled island chains in the western Pacific to help stem Japanese aggression in the Pacific, stressed the need for a large transport aircraft to carry huge payloads over long distances to war zones in Europe and the Pacific. In January 1942, Douglas commenced design studies for a heavy-lift transport aircraft designated the Model 415, which had a wingspan of 207 feet (63.14 meters), a bug-eye cockpit, and four Pratt & Whitney R-4360 Wasp Major radial engines. The initial Model 415 design would have carried two T9E1 tanks, two 105 mm howitzers, two angle dozers, or three disassembled P-40 Warhawk fighters. The US Army Air Force, however, judged the Model 415 too expensive to procure in quantity, so in February Douglas offered a revised long-range transport design, the Model 415A. The Model 415A design spanned 173 feet (52.84 meters), weighed 33 percent less when fully loaded and used four Wright R-3350 Duplex Cyclones; an alternate layout was conceived with six radial engines (possibly the Pratt & Whitney R-2800 Double Wasp). The USAAF approved the Model 415A design because of the lower unit cost compared to the original Model 415, and in March 1942 Douglas began the process of freezing the Model 415A design, now formally designated C-74; a contract was signed on June 25 for 50 aircraft and one static test article. By April 1943 the C-74 design process was finalized when the R-4360 was substituted for the R-3350, and in early March 1944 manufacture of the first C-74 airframes began at a new Douglas factory in Long Beach. Due to development of the XB-42 Mixmaster tactical bomber and XB-43 Jetmaster prototype jet bomber as well as production of the A-26 Invader attack aircraft, it was not until September 5, 1945 that the C-74 Globemaster made its first flight, by which time World War II was over. The end of the war also meant that the production contract was reduced to the 14 aircraft that left the assembly line. The C-74 was the biggest American landplane to enter production at the time of its first flight, and it had maximum weight of 172,000 lb (78,000 kg), with the ability to carry 125 soldiers or 48,150 lb (21,840 kg) of cargo over a range of 3,400 miles (5,500 km). Eleven C-74s were delivered to the Air Transport Command (later renamed the Military Air Transport Service in 1948) beginning in 1946, and they played a role in airlifting supplies and transporting wounded servicemen during the 1948 Berlin Airlift and the Korean War. The C-74 was subsequently retired from service in 1959, although a few aircraft served with civilian customers for years until 1969. In an interesting footnote, Douglas proposed an airliner version of the C-74 to carry 108 passengers, the DC-7 (not to be confused with the Douglas DC-7 airliner of the 1950s), in response to a requirement by Pan American World Airways. However, the DC-7 was cancelled in 1946 because of rising development costs.
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| Top: Desktop model of the C-124 Globemaster II Bottom: C-124A Globemaster II (serial number 49-241) unloading military equipment at an airbase in South Korea, early 1950s |
After World War II, Douglas conceived several proposals for large military transport aircraft to utilize features of the C-74 Globemaster within an airframe that could haul heavy military equipment. The first two design studies, the Models 1036 and 1040 conceived in June 1946, were high-wing designs with deep, rectangular-sided fuselages and rear opening clamshell doors beneath an extended upper fuselage. The Model 1036 had a wingspan of 172 feet 3 in (62.50 meters), while the Model 1040 spanned 208 feet 9 in (63.63 meters). These proposals were followed in 1947 by the Model 1105, which came in two variants, the 164 foot (50 meter) span Model 1105A-T with two vertical stabilizers and four R-4360s driving two pusher propellers and the conventional 209 foot (63.7 meter) span Model 1105A-C. In the end, Douglas opted for progressive development of the C-74, envisaging several C-74 derivatives with rear ramps, turboprop engines, or bigger fuselages ('XC-74X', Model 1040, Model 1041, Model 1106, Model 1110, Model 1113, Model 1114, Model 1119, Model 1122, Model 1128, and Model 1129). By November 1947, the ultimate progressive C-74 development, the Model 1129, which had a deeper fuselage and bow doors as well as conventional cockpit, was submitted to the Air Force and approved for full-scale development, receiving the designation C-124 and the official name Globemaster II. The fifth C-74 airframe (serial number 42-65406) was used in the construction of the C-124 prototype, which first flew on November 27, 1949. The first production C-124 was delivered the US Air Force on April 23, 1950, and a total of 448 C-124s were built, serving USAF strategic airlift needs during the Korean and Vietnam Wars. Two C-124 variants were built, the baseline C-124A (Model 1196) and the C-124C (Model 1317) with uprated Wasp Majors, new propellers, and a few other minor changes; the C-124B (Model 1197) would have had revised R-4360s but did not reach the hardware phase. The C-124 also was used to transport Thor intermediate-range ballistic missiles to England, and it also was involved in Operation Deep Freeze to supply US military bases in Antarctica.
Douglas YC-124B Globemaster II
In the early 1950s, Douglas began to investigate fitting the C-124 Globemaster II with turboprops, and two turboprop-powered C-124 variants were conceived, the Model 1182 with four Pratt & Whitney T34 turboprops and the Model 1183 with four Allison T40s. Three variants of the Model 1183 were devised, the Model 1183B and Model 1183E tankers, and the Model 1183D transport. The Model 1182, for its part, was originally designated YC-127, but was later redesignated YC-124B. Besides the turboprops, the YC-124B had a pressurized cockpit, the vertical stabilizer's fabric surface made from metal, and larger horizontal stabilizers. The first flight of the YC-124B took place in February 1954, and test flights showed it to have greater airspeed than the baseline C-124. However, the main drawback with the YC-124B was that its turboprop engines only operated efficiently at high altitude, but also its range being half of the C-124C at 12,000 feet (3,691 meters) and the cabin being unpressurized. Douglas proposed a tanker version of the Model 1182 as the KC-124B, to replace the KC-97s in service with the US Air Force because the KC-97 was slower than the B-36 and B-47 but also the upcoming B-52 Stratofortress, but the KC-124B never progressed beyond the drawing board.
References:
Berlin, E., 2000. Air Force Legends Number 206: Douglas C-124 Globemaster II. Simi Valley: Steve Ginter.
Cox, G., and Kaston, C., 2019. American Secret Projects 2: U.S. Airlifters 1941 to 1961. Manchester, UK: Crécy Publishing.
Williams, N., 2020. Air Force Legends Number 223: Douglas C-74 Globemaster. Simi Valley: Steve Ginter.
