Boeing C-97 Stratofreighter

Boeing C-97 Stratofreighter
Name	C-97 Stratofreighter
Type	Strategic transport aircraft
Manufacturer	Boeing
First flight	9 November 1944
Introduced	1947
Retired	1978
Primary user	United States Air Force
Number built	77
Developed from	Boeing B-29 Superfortress
Developed into	Boeing 377 Stratocruiser

Boeing C-97 Stratofreighter was a long-range heavy military transport aircraft developed from the Boeing B-29 Superfortress bomber. It entered service with the United States Air Force in 1947 and was a key component of Military Air Transport Service operations during the Cold War. The double-deck design, featuring a distinctive "double-bubble" fuselage, provided significant cargo capacity and led to the commercial Boeing 377 Stratocruiser.

Development and design

The development of the C-97 was initiated by Boeing to meet a United States Army Air Forces requirement for a heavy cargo transport. The design leveraged the wings, engines, tail, and lower fuselage of the Boeing B-29 Superfortress, mating them with a new, larger upper fuselage to create its unique double-deck cross-section. This "double-bubble" design, where two cylindrical fuselages were joined side-by-side, was pioneered by Boeing on the earlier Boeing 307 Stratoliner and provided immense internal volume. The first flight of the prototype, designated the XC-97, occurred on 9 November 1944 at Boeing Field in Seattle. The aircraft was powered by four Wright R-3350 Duplex-Cyclone radial engines, similar to those on the B-29 Superfortress, but later production models featured more powerful versions. The design emphasized strategic airlift capability, with a large rear clamshell door and ramp for loading vehicles and bulky cargo directly into the lower fuselage hold.

Operational history

The C-97 entered operational service with the Military Air Transport Service in 1947, at the dawn of the Cold War. It quickly became a workhorse for global strategic airlift, supporting operations like the Berlin Airlift and the Korean War, where it transported vital supplies, equipment, and personnel. The aircraft's long range was instrumental in establishing and sustaining global United States Air Force logistics networks, including flights across the Atlantic Ocean and the Pacific Ocean. Specialized variants, such as the KC-97 Stratotanker, provided critical aerial refueling for fighters and bombers like the B-47 Stratojet and B-52 Stratofortress. The C-97 also saw service during the Vietnam War, primarily in support roles. It was gradually phased out of active duty in the 1960s and 1970s in favor of jet-powered transports like the Lockheed C-141 Starlifter, with the last examples retired from the Air Force Reserve and the Israeli Air Force by 1978.

Variants

The primary variants of the C-97 series included the initial **YC-97** service test aircraft and the **C-97A**, the first production model equipped for cargo and troop transport. The **C-97C** was a medical evacuation version fitted as a flying ambulance. The most numerous variant was the **KC-97 Stratotanker**, a dedicated aerial refueler equipped with a flying boom and auxiliary jet engines to maintain formation with faster jet aircraft. Other notable variants included the **C-97G**, a multi-role transport converted from KC-97 tankers, and the **EC-97**, which served as an electronic intelligence platform. The commercial airliner derivative was the Boeing 377 Stratocruiser, operated by carriers such as Pan American World Airways and British Overseas Airways Corporation.

Operators

The primary military operator was the United States Air Force, including its Strategic Air Command, Military Air Transport Service, and Air National Guard units. The Israeli Air Force operated several C-97 and KC-97 aircraft, using them extensively in transport and refueling roles during conflicts like the Six-Day War and the Yom Kippur War. A small number of aircraft were also operated by the Spanish Air Force. Following military service, many airframes were sold to civilian cargo operators, with companies like Trans Mediterranean Airways and Aero Spacelines using them for freight and outsized cargo transport, the latter modifying them into the famous "Guppy" series of aircraft.

Specifications (C-97G)

* **Crew:** 5 (pilot, co-pilot, navigator, flight engineer, loadmaster) * **Capacity:** 96 troops or 69 litters * **Length:** 110 ft 4 in (33.63 m) * **Wingspan:** 141 ft 3 in (43.05 m) * **Height:** 38 ft 3 in (11.66 m) * **Empty weight:** 82,500 lb (37,422 kg) * **Max takeoff weight:** 175,000 lb (79,379 kg) * **Powerplant:** 4 × Wright R-4360 Wasp Major radial engines, 3,500 hp (2,600 kW) each * **Maximum speed:** 375 mph (603 km/h, 326 kn) * **Range:** 4,300 mi (6,900 km, 3,700 nmi) * **Service ceiling:** 35,000 ft (11,000 m)

Aircraft on display

Several C-97 and KC-97 aircraft are preserved in museums. Examples include a KC-97L at the National Museum of the United States Air Force at Wright-Patterson Air Force Base in Ohio, a C-97G at the March Field Air Museum in California, and a KC-97G at the Pima Air & Space Museum in Arizona. An Israeli Air Force KC-97 is displayed at the Israeli Air Force Museum near Be'er Sheva. The Museum of Flight in Seattle also holds a Boeing 377 Stratocruiser, the commercial counterpart to the military Stratofreighter.

Category:United States military transport aircraft 1940–1949 Category:Boeing aircraft Category:Cold War military aircraft of the United States