<p>In 1947 Douglas proposed to the Army Air Force (about to become the blue-suited Air Force) that it should develop a version of the C-74 Globemaster I with a fuselage designed for heavy cargo operations, instead of being modified from a commercial passenger carrier. After some discussion this was agreed; in fact, the resulting aircraft promised to do a far bigger job even than the C-74. Money was tight, but funds were found for a single aircraft, to be designated C-124A Globemaster II. This aircraft, 48-795, was preceded by the fifth C-74 (42-65406), which, partly at company expense, was rebuilt at Long Beach as the YC-124 prototype.
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<p>The fact that a C-74 could be rebuilt into the YC-124 shows the basic similarity. The fuselage, however, was completely new. As it was unpressurized, the fuselage no longer had to be of substantially circular cross-section, and the fuselage was almost doubled in depth, so that over most of its length the structure was 13 ft (3.9 m) wide and 13 ft (3.9 m) high. The forward section, however, was made even deeper still. The entire underside of the nose was occupied by a huge entry ramp, with left and right clamshell doors opening sideways and upwards to leave an opening 11 ft 8 in (3.5 m) high and 11 ft 4 in (3.4 m) wide, through which vehicles could drive straight on to the main deck. The latter was larger than in the C-74, the length being increased to 77 ft (23.4 m) and the height to 13 ft (3.9 m). This increased internal usable volume to more than 10,000 cu ft (28,317 m<su>3</su>), almost certainly more than in any other aircraft then built except the Hughes Hercules flying-boat. The cargo hoist and travelling cranes of the C-74 were retained.
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<p>The only other significant changes were to strengthen the landing gears for the increased gross weight of 175,000 lb (79,380 kg) and to relocate the relief crew compartment, with galley, toilet and bunks for six, at the rear of the flight deck on the upper level. In the C-74 these facilities had been on the lower floor under the flight deck. There was initially no change in maximum payload or fuel capacity, and the YC-124 was at first less powerful than the standard C-74 with 3,000-hp (2,238-kW) R-4360-35 engines, driving Hamilton Standard four-bladed propellers. It made its maiden flight on 27 November 1949. Later, this aircraft was re-engined with 3,500-hp (2,671-kW) R-4360-49 engines, and finally with 3,800-hp (2,834-kW) R-4360-35As with water injection.
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<p>Beyond doubt this cavernous monster was impressive, and before the YC flew the USAF had increased its order. In fact, ultimately it bought no fewer than 447 Globemaster IIs, beginning with 204 C-124As. These were powered by 3,800-hp (2,834-kW) R-4360-20W engines driving three-bladed reversing Curtiss propellers of 16-ft 7-in (5-m) diameter. With Douglas Model Number 1129A, they differed from the YC only in detail, and in being delivered with structural beams and floor panels to convert the interior into a double-deck aircraft. In this configuration 200 troop seats could be fitted; alternatively, the C-124 could be equipped with pillars to hold 136 (later revised to 127) stretchers, plus seats for 52 sitting patients and attendants. In this ambulance role the Globemaster II played an important role in bringing back casualties from the Korean War, but lack of pressurization restricted cruising height to 10,000 ft (3,048 m), a typical speed being 230 mph (370 km/h). With full payload of about 50,000 lb (22,680 kg), the combat radius was published at 1,000 miles (1,600 km), and range with 26,375 lb (11,963 kg) was about 3,000 miles (4,827 km).
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<p>The lead aircraft of the fifth production batch, 51-0072, was completed as the sole Douglas Model 1182E, ordered by the USAF as the YKC-124B, the prototype of a planned production tanker/transport with a pressurized fuselage and both flying boom and hose-drogue inflight-refueling installations. In the event this was cancelled, the only tanker adopted at that time being the TAC KB-50 and SAC KC-97, and the YKC-124B was cancelled. Instead, aircraft 51-0072 was taken over by USAF Air Research and Development Command as a major research vehicle to investigate the problems of turboprop propulsion, all tanker equipment being deleted. The new fuselage was retained, however, the undernose clamshell doors being deleted and the flight compartments pressurized for operation at over 30,000 ft (9,144 m). A major structural change was to strengthen the airframe for flight at indicated airspeeds increased by approximately 50 per cent, and the tail was redesigned with a horizontal surface of a high-speed aerofoil section and a fin and rudder increased in height.
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<p>Designated YC-124B, the turboprop aircraft was planned to solve many of the problems expected with the Douglas C-133 Cargomaster, and it was fitted with earlier versions of the engines planned for that aircraft, the Pratt & Whitney T34. The YC-124B made its first flight on 2 February 1954 powered by four 5,500-shp (4,103-kW) T34-1 engines, but subsequently received 6,000-shp (4,475-kW) T34-3 engines driving 18-ft (5.5-m) Curtiss Turbolectric propellers, the whole installation closely resembling that of the C-133. A further major change was that combustion heaters were fitted in streamlined pods on the wingtips to supply hot air to de-ice the leading edges of the wings and tail and, when necessary, to heat the flight compartment. This aircraft had a height increased from 48 ft 3in (14.7 m) to 51 ft 3 in (15.6 m), and a maximum take-off weight of 200,000 lb (90,720 kg).
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<p>When Douglas developed the C-124 it expected to make perhaps 50. The massive orders for 204 of the C-124A version stemmed entirely from the Korean War, and this conflict led to an improved version, the C-124C. With Douglas Model Number 1317, this incorporated all the experience gained with operating the A model, and also introduced several important modifications. The engines were Ford-built R-4360-63As, rated at 3,800 hp (2,834 kW) with water injection. The propellers remained three-bladed Curtiss, but with diameter increased from 16 ft 7 in (5.0 m) to 17 ft (5.1 m). Most important of all, fuel capacity was increased from 11,000 US gal (41,640 liters) to almost 14,000 US gal (55,000 liters), the maximum take-off weight having been permitted to rise to 194,500 lb (88,225 kg). The wingtip combustion heaters, used on the YC-124B, were adopted as standard. A further important upgrade was to fit APS-42 weather radar in a 'thimble' nose radome. The heaters and radar were subsequently retrofitted on most C-124As, eliminating the easy way of telling the two versions apart.
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<p>Douglas Long Beach handled the entire C-124 program with impressive speed, the first C-124A being delivered in May 1950, a month before the start of the Korean War, and the final C-124C being delivered in May 1955. The 447 production aircraft served with the USAF in every part of the world. As well as MATS (Military Air Transport Service) they served with SAC, TAC, Air Materiel Command and Far East Air Forces. One of their most urgent tasks was to fly nearly all the 60 SM-75 Thor IRBMs to RAF bases in England. At this time the bigger, faster and much more powerful C-133 was only just entering service, and the C-124s did a fine job trucking not just the 60 big missiles but also nearly 40,000 tons of supporting equipment, such as RP-1 and liquid-oxygen storage tanks, transporter/erectors and a vast amount of equipment to go into the site buildings. Transfer of the Globemaster IIs to the Air Force Reserve began in 1961. Globemasters served faithfully until the late 1960s, performing excellently on the air bridge to Southeast Asia. Only with the introduction to service of the Lockheed Galaxy could 'Old Shaky' retire gracefully, for it took an aircraft the size of the C-5 to replace the Globemaster's outsize load capacity. Ten Air National Guard units flew the type from January 1966, the 158th MAS/Georgia ANG giving up its Globemasters for Hercules in 1974 when the unit flew the last two USAF C-124s to the boneyard on 2 Sep[tember.
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<p>A single C-124C, 52-1069, was the testbed for the Pratt & Whitney YT57 turboprop. This huge engine, based on the J57 turbojet and rated at 15,000 shp (11,190 kW), drove a giant Hamilton Standard B48 four-bladed propeller with hollow steel blades. It was intended to power the four-engined Douglas C-132, cancelled in 1957. In the C-124C testbed it was mounted in the nose. In the years since then the Western world has failed to produce any shaft-drive engine in this power class.
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<hi style=hdr1>Specification</hi>
<hi style=hdr2>Douglas—C-124 Globemaster II</hi>
<list style=aflst>
<item><hi format=bold>Powerplant:</hi> four Pratt & Whitney R-4360-63A radial engines, each developing 3,500 hp (2,834 kW)
<item><hi format=bold>Dimensions:</hi> wing span 174 ft (53.07 m); length 130 ft 5 in (39.75 m); height 48 ft 3 in (14.72 m); wing area 250.6 sq ft (232.81 m)
<item><hi format=bold>Weights:</hi> empty 101,164 Ib (45,888 kg); maximum take-off 194,500 lb (88,224 kg)
<item><hi format=bold>Performance:</hi> maximum speed at sea level 270 mph (436 km/h); cruising speed 230 mph (370 km/h) at 10,000 ft (3,050 m); initial climb rate 625 ft (190 m) per minute; service ceiling 18,400 ft (5,610 m)
