The Douglas Globemaster & Cargomaster Transports

After World War II, Douglas Aircraft provided a series of heavy transports for the US Air Force. While the Douglas "Globemaster" piston transport was only built in small numbers, it led to the improved "Globemaster II", which was an airlift workhorse well into the Vietnam War. Douglas also built a large turboprop transport, the "Cargomaster", that served in the 1960s. This document provides a short history of the Globemaster, Globemaster II, and Cargomaster.

In early 1942, the Douglas Aircraft Company began design studies of a new heavy, long-range four engine transport aircraft, with the company designation of "Model 415", with an eye towards logistical support of operations in the Pacific theater. The work led to a formal US Army Air Forces (USAAF) contract in June 1942, specifying delivery of 50 of the transports. The aircraft was given the military designation of "C-74 Globemaster".

Although the design was as straightforward as possible to ensure that the aircraft could be put into production rapidly, the USAAF wanted Douglas to give higher priority to the A-26 Invader medium bomber, and the first C-74 wasn't rolled out until July 1945. It didn't perform its first flight until a few weeks after the end of the war, on 5 September 1945. At the time, it was the biggest land-based transport aircraft in the world.

The C-74 was basically a scaled-up DC-4 / C-54, with a low wing, four engines, conventional tail, and tricycle landing gear with twin wheels on each unit. The engines were Pratt & Whitney (P&W) R-4360-27 Wasp Major 28-cylinder four-row air-cooled radials with 2,238 kW (3,000 HP) each, driving fully reversible Curtiss electric propellers to permit shorter landings and improved taxi maneuverability. The wings featured a sophisticated arrangement of flaps to permit shorter takeoffs.

The C-74 had a crew of five, including copilot, pilot, radio operator, navigator, and flight engineer. Crew rest quarters were included for long-duration missions. Passageways were provided in the wing to permit the flight engineer to perform servicing and repairs while the machine was in flight.

One unusual feature of initial-build Globemasters was that the pilot and copilot sat in individual "blister" or "bug-eye" type canopies to give them maximum all-round visibility. Since this scheme also complicated interactions between the two men, it was changed to a more conventional cockpit arrangement. Which aircraft had the bug-eye cockpit scheme and which did not; when it was implemented; and whether the conventional cockpit scheme was retrofitted to early aircraft is unclear.

The C-74 could carry 125 fully-equipped troops, 115 litter patients with their medical attendants, or up to 22,675 kilograms (50,000 pounds) of cargo. The cargo bay had twin hoists that could be moved on a rail up and down the bay. They could be used to drop a removeable belly section to ease loading of cargoes, reducing the need for specialized cargo handling equipment.

Douglas began discussions with Pan American World Airways in 1944 for sale of an airliner version of the C-74 for commercial service after the war. The "civilian" C-74 was to be designated the "DC-7", though Pan Am called it the "Clipper Type 9". Pan Am ordered 26 DC-7s in June 1944, but the price kept climbing and the order was cancelled in October 1945. Similarly, although the USAAF contract had specified fifty C-74s, the order was cut back at the end of the war, and only fourteen C-74s were built. There was no "XC-74" prototype or "YC-74" evaluation aircraft as such. One of the 14 crashed in flight testing in August 1948 and another was a static test article that was tested to destruction.

The small numbers of C-74s built meant that the aircraft's service was limited, but it did give the US Air Force (USAF, as the USAAF had become in 1947) experience with the operation and usefulness of large transport aircraft.

The C-74 did achieve distinction during the Berlin Airlift in 1948. On 24 June of that year, the Soviets closed all land routes into the divided city of Berlin, Germany. The next day the USAF began "Operation Vittles", a massive airlift operation to keep the city supplied.

One Globemaster, the 13th built, arrived at Frankfurt Rhein-Main Airfield on 14 August to join in the airlift. The C-74 proved a very useful asset, hauling large quantities of supplies and often performing several trips in a day. On 18 September, the C-74 flew a total of six round trips. The single C-74 was instrumental in helping build Tegel Airfield in the French sector of Berlin, hauling in heavy construction equipment that had been dismantled into components. The aircraft operated as part of the airlift for six weeks, but it was simply too heavy for the Berlin runways. There are also stories that the Soviets complained that it might be used as a bomber because of its hoist well in the belly.

With the small number of C-74s in service, maintenance was an increasing headache as time went on and spares became harder to obtain, forcing the type's withdrawal from service. The last C-74 was finally retired from USAF service on 31 March 1956.

Douglas C-124 Globemaster II

The Air Force found the C-74 a very capable and useful aircraft, and began to consider acquiring much larger numbers of an improved version proposed by Douglas. The result was the "C-124 Globemaster II".

The C-124 used the same wings, tail, and engines as the C-74, but featured a new and enlarged fuselage, as well as stronger landing gear to handle higher weights. It was powered by four P&W R-4360-63A radial engines, with 2,835 kW (3,800 HP) each.

The "YC-124" prototype, rebuilt from a C-74, performed its initial flight on 27 November 1949. The Globemaster II had "clamshell" doors in the nose with hydraulically-activated loading ramps. The cargo bay, which was 23.5 meters (77 feet) long, featured the overhead hoist and removeable belly section of the C-74. Each hoist had a load capacity of 7,250 kilograms (16,000 pounds).

The C-124 could carry most Army field vehicles without requiring that they be dismantled. It could lift 33.560 kilograms (74,000 pounds) of cargo. Its double-decked cabin could also be fitted with 200 seats for troops, or with 123 litters for casualty evacuation. Flight crew numbered six.

The first operational C-124 was delivered in May 1950. A total of 204 "C-124As" were built, to be followed by 243 "C-124Cs". A turboprop-powered "KC-124B" tanker variant was considered, which emerged as a single "YC-124B" transport prototype that flew in 1954.

The C-124C featured uprated engines, an AN/APS-42 weather radar with a distinctive nose "thimble" radome, and wingtip-mounted combustion heaters to provide cabin heating and wing de-icing. The radar was retrofitted to most C-124As; some sources claim the heaters were as well, but others say not. The last of 448 Globemaster IIs was rolled out in May 1955. At the type's peak in 1963, there were 377 C-124s in service with 20 transport squadrons.

The C-124 provided valuable service in both the Korean and Vietnam Wars, though by the Vietnam era it was regarded as too slow. It was given a variety of nicknames by its crews, such as "Old Shakey", the "Shakemaster", the "Aluminum Cloud", or "Aluminum Overcast". The Globemaster II also performed many other duties, including Antarctic resupply missions, refugee evacuation, and disaster relief. The type was finally replaced by the Lockheed C-5 Galaxy in 1970.

Douglas C-133 Cargomaster

The last of the big Douglas prop transports was the "C-133 Cargomaster", which was designed in response to the Air Force's 1952 "Logistic Carrier Support System SS402L" requirement, to carry outsize cargoes. Douglas began work on the type in early 1953, and was awarded a contract for twelve "C-133As" in 1954.

The first "C-133A" performed its initial flight on 23 April 1956. There was no formal prototype, with initial delivery to the USAF Military Air Transport Service (MATS) in August 1957. C-133As began international flight operations the next year, and quickly set several records for transport aircraft. By the time of the C-133A's operational introduction, the US was engaged in a frantic race to build ballistic missiles, and one of the primary roles of the C-133A turned out to be ferrying the missiles from the manufacturer to operational sites.

Conceptually, the C-133 looked much more like an elongated Lockheed C-130 Hercules than the C-74 and C-124. The Cargomaster had a high, straight wing, with main landing gear in fairings alongside the aircraft to ensure an unobstructed cargo bay. The cargo bay was 27.5 meters long and 3.7 meters high (90 feet by 12 feet), had a volume of 1,210 cubic meters (13,000 cubic feet), and was pressurized, heated, and ventilated.

Early production C-133As were powered by four P&W T34-P-3 turboprops with 4,476 kW (6,000 SHP) each, but later machines were fitted with T34-P-7WA turboprops with 4,849 kW (6,500 SHP) each and water-methanol injection for boost power, The aircraft had a crew of four, and could carry 50,000 kilograms (110,000 pounds) of cargo, or a fully-assembled Jupiter, Thor, or Atlas ballistic missile. 200 airline-type seats could also be fitted, at least in principle.

The Cargomaster could be loaded through a side door on the right side of the aircraft, or a rear door. The first 32 C-133As had a two-section rear door that opened up and down, with the bottom section forming a loading ramp, while the last three had side-opening "clamshell" doors that extended the cargo bay by 90 centimeters (3 feet), allowing the aircraft to carry an assembled Titan missile.

The 35 C-133As were followed by 15 "C-133Bs", with the clamshell doors and uprated Pratt & Whitney T34-P-9W turboprops with 5,595 kW (7,500 HP) each. The last Cargomaster was rolled out in April 1961.

The C-133 served through the 1960s. It was a very big aircraft that gave the Air Force a very useful heavy-lift capability, but it was not very successful. The turboprop engines were unreliable, leading to poor flight availability rates, and they also caused excessive vibration, It had a number of other problems as well, some of which led to disastrous accidents and groundings. It was never used as a troop transport and it appears to have been generally disliked or even feared by anyone who had anything to do with it. Airframe fatigue problems finally led to the Cargomaster's withdrawal from service in 1971, to the relief of all concerned.

It was replaced by the Lockheed C-5 Galaxy , which ironically would also suffer from premature fatigue problems. A handful of C-133s remained in commercial service for a few years after the type's withdrawal from military service.

Author: Greg Goebel