In the latter half of 1935, even before the Douglas Sleeper Transport (DST) and DC-3 had flown, United Air Lines began discussions with the Douglas Airplane Company regarding a four-engined aircraft that could carry twice as many passengers as the DC-3 and had a range of 2,200 miles (3,541 km). [In U.S. Navy (USN) service, the DC-3 was designated R4D, q.v.] By February 1936, American, Eastern and Transcontinental & Western Airlines (TWA) and Pan American World Airways also showed a considerable interest and joined United in funding the project. A very revolutionary aircraft evolved as the design work progressed. The new aircraft, designated the Douglas Commercial Model Number 4 (DC-4), was large and capable of carrying 42 day passengers and 30 night passengers with full sleeping accommodations including a private bridal suite. Passenger amenities included electric shavers, hair curlers, wardrobes, washrooms and toilets. Technically, the aircraft had a tricycle landing gear, triple fins and rudders, power-boosted controls, an auxiliary power system and air conditioning. Although not fitted on the prototype, the production aircraft were to be fully pressurized. As the design progressed, Pan American and TWA became concerned about the complexity of the aircraft and withdrew their support and ordered the Boeing Model 307 Stratoliner.

The DC-4 made it=92s first flight on 7 June 1938, received it=92s Approved Type Certificate (ATC) on 5 May 1939 and was delivered to United Air Lines. United began testing and found that the aircraft did not possess any vices but it=92s performance did not meet expectations, the complexity of the systems resulted in considerable maintenance problems and the anticipated economies did not materialize; United rejected the aircraft and returned it to Douglas. The one and only DC-4, now designated DC-4E, E for experimental, was sold to Greater Japan Air Lines (Nippon Koku K.K.) in late 1939. After being flown for a short time, the Japanese reported that it had crashed in Tokyo Bay. Actually, the Japanese Navy had ordered the DC-4E to be secretly delivered to Nakajima Hikoki K.K.and disassembled for study. Nakajima built the first G5N1 Navy Experimental 13-Shi Attack Bomber Shinzan using the wing, engine installation and landing gear of the DC-4E; the fuselage was new. Unfortunately, the Japanese had based their design on an unsuccessful aircraft and the G5N was underpowered, complex and featured poor performance. Four G5N1's and two G5N2's were built; the G5N2's were used as freight transports during the war and were given the Allied Code Name Liz.

With the failure of the DC-4E, Douglas, supported by American, Eastern and United Air Lines, began work in 1939 on a new aircraft that was lighter, simpler, cheaper, easier to maintain with good operating economies. The DC-4E design was scrapped and a new aircraft, also designated DC-4, was designed. The =93new=94 DC-4 was a four-engined, all-metal, unpressurized, low-wing monoplane with a retractable tricycle landing gear, single vertical tail assembly, smaller wing and 25 percent lighter. The rudder and elevators were fabric covered. The aircraft was powered by four Pratt & Whitney R-2000 14-cylinder, twin-row, air-cooled radial engines with two-speed superchargers driving three-bladed Hamilton-Standard Hydromatic constant-speed full-feathering propellers. This aircraft could accommodate 40 passengers by day or 28 by night.

By 1941, orders for 61 DC-4's had been placed by U.S. airlines but none of them were ever delivered. The U.S. military began a buildup in 1940 and the U.S. War Department took over all production of the DC-4 on 28 June 1941 and allocated them to the U.S. Army Air Forces (USAAF) as C-54 Skymasters. (Other DC-4's were designated XC-114, XC-115 and YC-116 by the USAAF.) The military version had a crew of six, pilot, co-pilot, navigator, radio-operator and two relief crew. The crew compartment contained bunks, toilet, water tank and space for storing parachutes, life rafts, etc.

In order to avoid conflicting priorities, the USAAF was charged in 1941 with ordering all DC-4's for military service, whether they be for the USN or Lend Lease. By the end of World War II, a total of 1,163 DC-4's had been produced for the military and were in use by the USAAF, USN, and the Royal Air Force (RAF).

There was no prototype DC-4/C-54 built. The first 24 aircraft, equivalent to the civilian DC-4, were designated C-54-DO and this aircraft made it=92s first flight on 14 February 1942; all 24 were delivered to the USAAF. The next version was the C-54A and these aircraft were the first fully militarized version of the DC-4. The USN accepted their first C-54A, which they designated R4D-1, on 22 February 1943; the Navy accepted a total of 202 C-54/R4D=92s between February 1943 and October 1945.

In 1962, the U.S. Department of Defense adopted a new, standard designation system based on the U.S. Air Force (USAF) system that was to be applied to all military aircraft. The R5D-1's through -5 were redesignated C-54N through C-54T and a prefix, rather than a suffix letter was used for aircraft that had been modified. The old and new designations are listed below in the Production History section

PRODUCTION HISTORY

R5D-1: Fifty seven C-54A-DC=92s and -DO=92s ordered by the USAAF and transferred to the USN between February 1943 and September 1944. These aircraft, powered by four 1,350 hp (1,007 kW) Pratt & Whitney R-2000-7 engines, were built at the Douglas Aircraft Company plants in Chicago, Illinois (-DC) and Santa Monica, California (-DO). This was the first fully militarized DC-4 and had a reinforced cabin floor, two large cargo doors  measuring 94 x 67 inches (2.39 x 1.70 meters) on the port (left) side aft of the wing, a built-in twin-boom cargo-loading hoist and capacity to carry up to 50 passengers in canvas bucket seats or 32,500 pounds (14,742 kg) of cargo. This aircraft also had provisions to carry heavy equipment beneath the fuselage.

R5D-1C: A few R5D-1's re-equipped with the R5D-2 fuel system.

R5D-1F: At least one R5D-1 converted to a VIP transport with 16 to 20 seats; redesignated R5D-1Z in 1945.

R5D-1Z: R5D-1F redesignated in 1945; redesignated VC-54N in 1962.

R5D-2: Thirty C-54B-DC=92s and -DO=92s ordered by the USAAF and transferred to the USN between August 1944 and January 1945. These aircraft were identical to the R5D-1's except (1) two of the four auxiliary fuel tanks in the cabin were removed and replaced by integral fuel tanks in the outer wing panels; (2) the cargo-loading hoist was removed from the latter block of aircraft; and (3) removable stretcher fittings were provided along with individual oxygen outlets throughout the cabin. These aircraft were built at the Douglas Aircraft Company plants in Chicago, Illinois (-DC) and Santa Monica, California (-DO) and were redesignated C-54P in 1962.

R5D-2F: At least four R5D-2's converted to VIP transports with 22 seats or ten bunks; redesignated R5D-2Z in 1945.

R5D-2Z: R5D-2F=92s redesignated in 1945;  redesignated VC-54P in 1962.
R5D-3: Ninety five C-54D-DC=92s ordered by the USAAF and transferred to the USN between February and October 1945; another ten, which had been delivered to the Royal Air Force (RAF) under Lend-Lease, were assigned to the USN when the RAF returned them after World War II:  another 127 were canceled. These aircraft had the same fuel tank arrangement as the R5D-2 but were powered by four 1,350 hp (1,007 kW) Pratt & Whitney R-2000-11 engines. All were built at the Douglas Aircraft plant in Chicago, Illinois and were redesignated C-54Q in 1962.

R5D-3P: One R5D-3 converted for the U.S. Coast Guard (USCG) as a photographic survey aircraft. Redesignated RC-54V in 1962

R5D-3Z: At least two R5D-3's converted to VIP transports with 22 seats or 10 bunks; redesignated VC-54Q in 1962.

R5D-4: Twenty C-54E-DO=92s ordered by the USAAF and transferred to the USN between February and May 1945. The two cabin fuel tanks of the R5D-2 and -3 were removed and replaced by collapsible bag-type tanks in the inner wings resulting in an increased fuel capacity. These aircraft could be rapidly transformed from a cargo aircraft capable of handling 32,500 pounds (14,742 kg) of cargo to a transport carrying 50 troops in bucket canvas seats or 44 passengers in airline-type seats. All were built at the Douglas Aircraft Company plants in Santa Monica, California and were redesignated C-54R in 1962.

R5D-4R: At least 15 R4D-4's converted to passenger transports with airline type seats; redesignated C-54R in 1962.

R5D-5: Sixty R5D-2 and -3 aircraft re-engined with 1,450 hp (1,081 kW) Pratt & Whitney R-2000-9 engines and approximating the USAAF=92s C-54G-DO. Redesignated C-54S in 1962.

R5D-5R: A few R5D-5's with passenger interiors, nose radar and electronic auto pilot; redesignated C-54T in 1962.

R5D-5Z: A few R5D-5's with VIP interiors consisting of 22 seats or 10 bunks; redesignated VC-54S in 1962.

R5D-6: Designation reserved for USN version of the USAAF C-54J-DO VIP transport; the aircraft was never built.

VC-54N: The R5D-1Z redesignated in 1962.

C-54P: R5D-2's redesignated in 1962.

VC-54P: R5D-2Z=92s redesignated in 1962.

C-54Q: R5D-3's redesignated in 1962.

VC-54Q: R5D-3Z=92s redesignated in 1962.

C-54R: R5D-4R=92s redesignated in 1962.

C-54S: R5D-5's redesignated in 1962

VC-54S: R5D-5Z=92s redesignated in 1962.

C-54T: R5D-5R=92s redesignated in 1962.

EC-54U: Two USCG R5D-4's converted for electronic countermeasures (ECM) training and testing and redesignated in 1962.

RC-54V: USCG R5D-3P redesignated in 1962.

OPERATIONAL HISTORY

The primary user of the R4D=92s in the USN was the Naval Air Transport Service (NATS). NATS was established on 12 December 1941 under the Chief of Naval Operations (CNO) to provide rapid air delivery of critical equipment, spare parts, and specialist personnel to naval activities and fleet forces worldwide. To accomplish it=92s mission, NATS was authorized to establish three wings, the Pacific, West Coast and Atlantic Wings. NATS squadrons operating the R5D included:

- Transport Squadron One (VR-1) at NAS Patuxent River, Maryland, was tasked with operating over the North Atlantic and was the first squadron to be equipped with R5D-1's enabling them to operated a route from the U.S. to Prestwick, Scotland via Reykjavik, Iceland. VR-1 continued to operate a mix of Douglas R4D=92s, q.v., and R5D=92s until the end of the war.

- VR-3 at NAS Olathe, Kansas, tasked with operations in the U.S., primarily operated the R4D but also operated R5D=92s in limited numbers.

- VR-4 at Naval Auxiliary Air Station (NAAS) Oakland, California also operated R4D=92s and a few R5D=92s.

- VR-5 at NAS Seattle, Washington was tasked with flying between the U.S. and the Territory of Alaska and also operated R4D=92s and a few=20 R5D=92s.

- VR-11 at NAS Honolulu, Territory of Hawaii was the largest operator of the R5D. By the end of the war, VR-11 had 700 pilots, 89 R5D=92s, ten R4D=92= s and three other aircraft. A VR-11 flight passed through NAS Honolulu every hour, 24 hours a day, seven days a week.

- Air Transport Evacuation Squadron One (VRE-1) was formed from VR-11 at NAS Honolulu and moved to Agana Airfield, Guam, Mariana Islands (13-20N 144-47E).

- Utility Transport Squadron One (VRJ-1) was formed at NAS Pearl Harbor, Territory of Hawaii and moved to NAS Honolulu in June 1944. This squadron was tasked with providing VIP transport services and operated R5D=92s, Consolidated PB2Y Coronado=92s, q.v., and a Beech JRB Expeditor, q.v.

The U.S. Marine Corps (USMC) received at least one R5D-5 in 1943.

After World War II, other USN, USMC and USCG units transitioned to the R5D. In July 1948, NATS and the USAF=92s Air Transport Command (ATC) were disbanded and their transport squadrons were assigned to the newly activated Military Air Transport Service (MATS). Three USN R5D squadrons, VR3, VR-6 and VR-8 were assigned to the new command. On 27 October 1948, VR-6 and VR-8 were ordered to fly their 24 R5D=92s to Germany to support the Berlin Airlift; they continued operations to Berlin until 31 July 1949. On 1 December 1949, the Fleet Logistic Air Wing was established to provide cargo and passenger transport for the USN and three R5D units, VR-1, VR-5 and VR-21, were assigned to the new command.

R5D=92s were assigned to the USMC after the war as cargo and passenger transport. In 1950, two units, Marine Transport Squadron One Hundred Fifty Two (VMR-152) and VMR-352, were operating R5D=92s. VMR-152 had one  R5D-2 serving as a flying Tactical Air Direction Center during the Korean War.

The USCG operated 15 Skymasters, nine of which had been acquired from the USN and six from the USAF. The first six R5D-3's were acquired from the USN in 1945. In addition to logistical and transport duties, these aircraft were used for search and rescue (SAR), service with the International Ice Patrol, photographic mapping and electronic testing. The last USCG R5D/C-54 was disposed of in 1965.

The last Navy Skymaster, a C-54Q (former R5D-3) operated by the Navy Test Pilot School, was retired in 1974.

SPECIFICATIONS

Wing Span: 117 feet 6 inches (35.81 meters)
Length: 93 feet 11 inches (28.63 meters)
Height: 27 feet 6.3125 inches (8.39 meters)
Wing Area: 1,462 square feet (135.8 square meters)
Empty Weight
   R4D-1: 37,300 pounds (16,919 kg)
   R4D-2: 38,200 pounds (17,327 kg)
   R4D-3: 38,000 pounds (17,237 kg)
Gross Weight
   R4D-1: 68,000 pounds (30,844 kg)
   R4D-2, -3 and -4: 73,000 pounds (33,112 kg)
Fuel Capacity
   R4D-1: 3,620 U.S. gallons (13,703 liters)
   R4D-2: 3,720 U.S. gallons (14,082 liters)
   R4D-4: 3,540 U.S. gallons (13,400 liters)
Maximum Speed: 274 mph at 14,000 feet (441 km/h at 4,267 meters)
Cruising Speed: 239 mph at 15,200 feet (384.6 km/h at 4,633 meters)
Initial Rate of Climb: 1,070 ft/minute (326 meters/minute)
Service Ceiling: 22,500 feet (6,858 meters)
Maximum Range: 3,900 miles (6,276 km) with 5,400 pounds (2,449 kg) of cargo
Armament: None