The C-97 Stratofreighter, a four-engine strategic transport, was the AAF cargo/transport version of the B-29. An enlarged fuselage section was built on top of the B-29's lower fuselage, giving the aircraft its characteristic figure-eight cross section. The C-97 Stratofreighter design used the wing, tail, and engines of the B-29 on a new double-lobe body that provided the volume required to transport troops and cargo. In mid-1942 Boeing proposed a transport variant of the B-29, and the Air Force accepted the first prototype in 1944. Between 1943 and 1950, 97 Stratofreighters were ordered; the first flight occurred on Nov. 15 1944.
The C-97 formed the basis of the Boeing Stratocruiser commercial airliner of the 1950s The C-97 would serve as a satisfactory strategic transport, but achieve its greatest fame and value in its air-to-air refueling role as an aerial tanker. The tanker version (KC-97) was introduced in 1950 using the "flying boom" refueling system and all subsequent USAF contracts for C-97s were for tankers. In all, 890 aircraft were ordered, 97 C-97s and 816 KC-97s. Boeing also attempted to capitalize on its investment by introducing a civilian version dubbed the Model 377 Stratocruiser. Several dozen of these aircraft were ordered by various airlines, but Douglas and Lockheed captured the market, making the last airliners of the piston age.
In addition to the C-74, the Berlin Airlift served as a test for another giant aircraft. On May 1, 1949, SAC's Boeing YC-97A "Stratofreighter" arrived in Germany. Along with the airplane came one SAC aircrew, seven maintenance personnel, and over ten tons of specialized parts. Later, additional maintenance personnel and enough people to make up three full crews arrived. Service tests of the YC-97A proved somewhat anticlimactic. Initial assessment of the aircraft showed several problems, including the length of the fuselage, which caused both fatigue and confusion, and the difference in height between trucks and its the deck, which necessitated borrowing a conveyor belt from a German company. The YC-97A aircraft flew 23 missions, delivering 444.8 tons of cargo to Berlin. On May 24, however, engine problems forced it to make an emergency landing during which it blew four tires and caused sufficient damage to close Gatow's runway for over seven hours. The YC-97A remained at the British base until three new engines arrived on June 17. The aircraft then returned to the United States.
The "48 Group Program" then in effect for Fiscal Year (FY) 1949 included the delivery of fifty, four-engine Boeing C-97 "Stratofreighters" between July 1949 and March 1950, and if Congress approved the air force's proposed "57 Group Program," a further fifty-four C-97s would be purchased [a total of 97, rather than 104, were built].
The Military Air Transport Service (MATS) had researched aircraft development in the Aeromedical Evacuation [AE] role before its formal organization. On 1 June 1950, the new MATS C-97A Strato-freighter was introduced into the AE role. With its larger carrying capacity and pressurized cabin, the weekly C-97A flight replaced the four trips per week flown by the C-54.
In 1958 air transport modernization was not at the top of the Air Force's procurement list. Defense officials, however, did show a moderate commitment to the congressional recommendations. They made ongoing plans to retire the MATS piston-engined C-54 Skymaster and C-97 Stratofreighter aircraft and to introduce the C-133 Cargomaster, at that time the largest turboprop transport in the Air Force.
After 1956 USAF KC-97s were gradually replaced by KC-135 jet tankers, but some were modified for continued use in other roles. In 1964, selected aircraft were returned to a tanker configuration (KC-97L) primarily for the Air National Guard. Two jet engines were added to increase speed and altitude, making the tankers more compatible with high performance jet aircraft. The C-97 "Stratocruiser" participated in numerous missions including support of high-profile Southeast Asia operations. Although the last USAF C/KC-97 was retired in 1973, examples remaned in use with the AF Reserve and ANG as tankers or air-sea search and rescue aircraft.
The Boeing HC-97G Stratocruiser was especially modified in 1964 for rescue work and served in limited numbers as an interim aircraft until ARRS units are fully equipped with the new HC-130H Lockheed Hercules. The Stratocruiser did an excellent job, its range, speed, and altitude providing a substantial increase in capability over another old workhorse, the HC-54, which was utilized most effectively from 1956 until July 1966.
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