Boeing C-97 Stratofreighter
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|Role||Military transport aircraft|
|First flight||9 November 1944|
|Primary users||United States Air Force|
Israeli Air Force
|Number built||77 (total of 888 in all variants)|
|Developed from||Boeing B-29 Superfortress|
Boeing B-50 Superfortress
|Variants||Boeing KC-97 Stratofreighter|
Boeing 377 Stratocruiser
Aero Spacelines Pregnant Guppy
Aero Spacelines Super Guppy
Aero Spacelines Mini Guppy
The Boeing C-97 Stratofreighter is a long-range heavy military cargo aircraft developed from the B-29 and B-50 bombers. Design work began in 1942, with the prototype's first flight being on 9 November 1944, and the first production aircraft entered service in 1947. Between 1947 and 1958, 888 C-97s in several versions were built, 811 being KC-97 tankers. C-97s served in the Berlin Airlift, the Korean War, and the Vietnam War. Some aircraft served as flying command posts for the Strategic Air Command, while others were modified for use in Aerospace Rescue and Recovery Squadrons (ARRS).
- 1 Design and development
- 2 Operational history
- 3 Variants
- 4 Operators
- 5 Accidents and incidents
- 6 Surviving aircraft
- 7 Specifications (C-97)
- 8 See also
- 9 References
- 10 External links
Design and development
The C-97 Stratofreighter was developed towards the end of World War II by fitting an enlarged upper fuselage onto a lower fuselage and wings which were essentially the same as those of the B-29 Superfortress with the tail, wing, and engine layout being nearly identical. It was built before the death of Boeing president Philip G. Johnson. It can be easily distinguished from the 377 Stratocruiser by the "beak" radome beneath the nose and by the flying boom and jet engines on later tanker models.
On 9 January 1945, the first prototype, piloted by Major Curtin L. Reinhardt, flew from Seattle to Washington, DC in 6 hours 4 minutes, an average speed of 383 mph (616 km/h) with 20,000 lb (9,100 kg) of cargo, which (at that time) was impressive for such a large aircraft. Production models featured the 3,500 hp (2,600 kW) Pratt & Whitney Wasp Major engine, the same engine as for the B-50. The tenth and all subsequent aircraft were fitted with the taller fin and rudder of the B-50 Superfortress.
The C-97 had clamshell doors under its tail, so that a retractable ramp could be used to drive in cargo. However, unlike the later Lockheed C-130 Hercules, it was not designed as a combat transport which could deliver directly to primitive forward bases using relatively short takeoffs and landings. The rear ramp could not be used in flight for air drops.The C-97 had a useful payload of 35,000 lb (16,000 kg) and could carry two normal trucks, towed artillery, or light tracked vehicles such as the M56 Scorpion. The C-97 was also the first mass-produced air transport to feature cabin pressurization, which made long range missions somewhat more comfortable for its crew and passengers.
The civilian derivative of the C-97 was the Boeing 377 Stratocruiser, a very luxurious transoceanic airliner which featured a lower deck lounge and could be fitted with sleeper cabins. The first Stratocruiser flew on July 8, 1947. Only 56 were built.
The C-97 entered service in 1947, during a period of rapid development of heavy transport aircraft. Only 77 were built before the C-124 Globemaster II was delivered in 1950, with nearly twice the payload capacity of the C-97. The USAF Strategic Air Command operated C-97 Stratofreighters from 1949–1978. Early in its service life, it served as an airborne alternative SAC command post. While only 77 C-97 transports were built, 811 were built as KC-97 Stratofreighters for inflight refueling. The KC-97 began to be phased out with the introduction of the KC-135 in 1957. Many KC-97s were later refitted as C-97G transports and equipped several squadrons of the US Air National Guard.
One YC-97A (45–59595) was used in the Berlin Airlift during April 1949 operating for the 1st Strategic Support Squadron. It suffered a landing gear accident at Gatow and by the time it was repaired, the Soviet Blockade was lifted.
C-97s evacuated casualties during the Korean War. C-97s also participated in the Biafran airlift, delivering relief materials to Uli airstrip in Biafra during the Nigerian Civil War. Flying under the cover of darkness and at treetop level to evade radar, at least two C-97s were lost.
Only one C-97 is still airworthy at the present day,(s/n 52-2718, named "Angel of Deliverance") operated by the Berlin Airlift Historical Foundation. It is painted as YC-97A 45-59595, the sole C-97 to participate in the Berlin Airlift.
The Israelis turned to Stratocruisers and KC-97s when they could not buy the preferred C-130. They adapted Boeing 377 Stratocruiser airliners into transports, including many using C-97 tail sections including the loading ramp. Others were adapted with swiveling tails and refueling pods. One Israeli C-97 was downed by an Egyptian SA-2 Guideline missile on 17 September 1971, while flying as an electronic counter-measures platform some 12 miles from the Suez Canal.
- military designation of the prototype Boeing 367, three built.
- cargo transport, six built.
- troop carrier, three built.
- fitted with 80 airliner-style seats, later redesignated C-97B, in 1954 became C-97D, retired to MASDC 15 December 1969.
- transport, 50 built.
- Three C-97As were converted into aerial refueling tankers with rear loading door removed and a flight refueling boom added. After the design was proven, they were converted back into the standard C-97A.
- Second production version, 14 built; those used as medical evacuation transports during the Korean War were designated MC-97C.
- staff transport and flying command post conversions, three C-97As converted.
- KC-97Es converted to transports.
- aerial refueling tankers with rear loading doors permanently closed; 60 built.
- KC-97Fs converted to transports.
- 3800hp R-4360-59B engines and minor changes; 159 built.
- 135 KC-97Gs converted to transports.
- ELINT conversion of three KC-97Gs. 53–106 was operated by the CIA for covert ELINT operations in the West Berlin Air Corridor.
- dual-role aerial refueling tankers/cargo transportation aircraft. KC-97G models carried underwing fuel tanks; 592 built.
- Five KC-97Gs were used as ground instruction airframes.
- One aircraft was modified to test the underwing General Electric J47-GE-23 jet engines, and was later designated KC-97L.
- KC-97Gs converted for search and rescue operations; 22 converted.
- One KC-97F was experimentally converted into a probe-and-drogue refueling aircraft.
- KC-97G conversion with four 5,700 hp (4,250 kW) Pratt & Whitney YT34-P-5 turboprops, two converted.
- 27 KC-97Gs converted to troop transports.
- 81 KC-97Gs modified with two J47 turbojet engines on underwing pylons.
U.S. Air Force units
The following Air Force wing organizations flew the various C-97 models at some time during their existence:
Air National Guard
- 105th Aeromedical Transport Group
– Westchester County Airport, New York (1962–1969)
- 137th Air Transport Squadron
- 106th Air Transport Group – Suffolk County Airport, New York
- 102d Air Transport Squadron
- 109th Air Transport Group – Schenectady Airport, New York
- 139th Air Transport Squadron
- 111th Air Transport Group – NAS Willow Grove, Pennsylvania
- 103d Air Transport Squadron
- 116th Air Transport Group – Dobbins ARB, Georgia
- 128th Air Transport Squadron (Heavy)
- 118th Air Transport Group – Berry Field Air National Guard Base / Nashville International Airport, Tennessee
- 105th Air Transport Squadron
- 126th Air Refueling Wing – O'Hare Airport, Illinois
- 108th Air Refueling Squadron
- 128th Air Refueling Wing - Gen. Mitchell Airport, Wisconsin
- 126th Air Refueling Squadron
- 133d Air Transport Wing – Minneapolis-St Paul International Airport, Minnesota
- 109th Air Transport Squadron (Heavy)
- 137th Air Transport Group – Will Rogers World Airport, Oklahoma
- 185th Air Transport Squadron
- 138th Air Transport Group – Tulsa Air National Guard Base / Tulsa International Airport, Oklahoma
- 125th Air Transport Squadron
- 139th Air Transport Group – Rosecrans Air National Guard Base, Missouri
- 146th Air Transport Wing – Van Nuys Air National Guard Base / Van Nuys Airport, California
- 115th Air Transport Squadron (Heavy)
- 195th Air Transport Squadron (Heavy)
- 151st Air Transport Wing – Salt Lake City Air National Guard Base / Salt Lake City International Airport, Utah
- 191st Air Transport Squadron (Heavy)
- 157th Air Transport Group – Grenier AFB, New Hampshire(1960–1964)/ Pease AFB, New Hampshire (1964–1968)
- 133d Air Transport Squadron (Heavy)
- 161st Air Transport Group – Sky Harbor International Airport, Arizona (1966–1972)
- 197th Air Transport Squadron
- 162d Air Transport Wing -, Arizona
- 164th Air Transport Group – Memphis Air National Guard Base / Memphis International Airport, Tennessee
- 155th Air Transport Squadron (Heavy)
- 165th Air Transport Group – Savannah Air National Guard Base / Savannah International Airport, Georgia
- 158th Air Transport Squadron (Heavy)
- 166th Air Transport Group – New Castle Air National Guard Base / Greater Wilmington Airport, Delaware
- 142d Air Transport Squadron
- Berlin Airlift Historical Foundation
- Foundation for Airborne Relief (USA)
- Hawkins & Powers Aviation
- Zantop Air Transport
Accidents and incidents
- 22 May 1947 – USAF XC-97 43-27472 crashed in a wheat field near Wright-Patterson Air Force Base and caught fire, killing five of seven crew on board.
- 6 June 1951 – USAF C-97A 48-0398 crashed near Kelly Air Force Base due to a possible asymmetric flap extension on takeoff, killing all nine crew on board.
- 15 October 1951 – After taking off from Lajes Field, Azores, USAF C-97A 49-2602 of the Military Air Transport Service went missing on a flight back to Westover Air Force Base, Massachusetts. The aircraft was piloted by Captain John Francis Dailey, Jr. and had a crew of 11. A total of 50 aircraft and ships searched the intended route but no trace of the aircraft or crew was ever found.
- 22 October 1951 – USAF C-97A 48-0413 crashed and burned next to a runway at Kelly AFB, killing four of six on board.
- 27 June 1954 – USAF KC-97G 52-2654 crashed into Box Springs Mountain, killing all 14 on board. The aircraft was diverting to Norton AFB due to poor weather at its destination, March AFB.
- 4 May 1955 – USAF KC-97G 53-0110 was flying in formation when it crashed into the Atlantic 90 mi off Iceland due to loss of control caused by an engine fire, killing all nine on board.
- 6 July 1956 – USAF KC-97E 51-0220 crashed in a wooded area 45 mi northeast of Goose Bay, Canada after reporting an engine fire, killing all six on board.
- 22 January 1957 – USAF KC-97G 53-0222 of the 384th Air Refueling Squadron crashed in the Adirondack mountain foothills while on a refueling training mission, killing all seven on board.
- 22 March 1957 – USAF C-97C 50-0702 en route to Tokyo went missing over the Pacific Ocean, with 10 crew and 57 passengers on board. It is the deadliest incident ever involving the C-97.
- 18 July 1957 – USAF KC-97G 52-2737 crashed in Lake Champlain due to double engine failure, killing six of eight on board.
- 29 October 1957 – USAF KC-97G 52-2711 struck a mountain in poor visibility 35 mi north of Flagstaff, Arizona during a survey flight, killing all 16 on board.
- 19 January 1958 – USAF C-97A 49-2597 en route to Wake Island from Honolulu went missing over the Pacific Ocean with seven crew on board.
- 22 July 1959 – USAF KC-97G 52-2703 of the 509th Air Refueling Squadron crashed near Andover, New Hampshire due to an in-flight fire while on a night time training mission, killing all seven on board. The fire was caused by a turbocharger bearing failure which then caused a fuel leak.
- 30 March 1960 – USAF KC-97F 51-0363 ditched in the Atlantic off Florida in high winds, killing two of 14 on board.
- 27 June 1960 – USAF KC-97G 52-2738 of the 380th Air Refueling Squadron was one of two KC-97G's in crew T-51 which were to refuel a B-47 under simulated combat conditions. 52-2738 was about to connect with the B-47 when the number one engine caught fire. The aircraft turned left and went into a spin. The outer portion of the left wing, weakened by the fire, separated and the aircraft crashed out of control into a mountain near Newry, Maine, killing all five on board.
- 29 June 1964 – USAF HC-97G 52-2773, along with USAF HC-54D 42-72590, were performing pararescue training and photography missions for the NASA Gemini program when the HC-54 banked to the right, colliding with the HC-97 and shearing off the wing and tail section; both aircraft crashed in the water off Bermuda, killing 17 on board both aircraft; seven survived after they jumped before the aircraft collided. The cause was probably incapacitation of the HC-54 pilot.
- 19 December 1964 – USAF KC-97G 52-907 ran off the runway at Ernest Harmon AFB after the pilot landed too far down the runway, killing all five on board. The pilot attempted to abort the landing, but the aircraft struck approach lights and crashed into a pond.
- 19 January 1969 – Wisconsin Air National Guard KC-97L 52-0904 crashed short of the runway at General Mitchell Airport, killing four of 11 on board.
- 26 September 1969 – A Nordchurchaid C-97G, (N52676), struck trees and crashed while on final approach to Uli Airstrip, killing all five on board.
- 30 November 1970 – Israeli Air Force KC-97G 4X-FPS/037 was being towed across runway 30 at Lod International Airport when it was struck by a TWA Boeing 707; both aircraft caught fire. Two people on the ground died.
- 17 September 1971 – Israeli Air Force KC-97G 4X-FPR/033 was shot down by Egyptian missiles after penetrating Egyptian airspace along the Suez Canal, killing seven of eight on board.
- 30 July 1987 – After taking off, a C-97G (HI-481) operated by Belize Air International (a cargo airline) crashed onto the Mexico City-Toluca highway after the cargo shifted, killing 5 of 12 on board and 44 on the ground.
- On display
- C-97G N117GA(52-2718) "Angel of Deliverance" - Berlin Airlift Historical Foundation of Farmingdale, New Jersey. It is painted as YC-97A 45-59595.
- On display
- C-97G 52-898 - Only vertical stabilizer preserved McGhee Tyson Air National Guard Base, Alcoa, Tennessee. Formerly displayed near Octave Chanute Aerospace Museum, Rantoul, Illinois. 
- C-97G 52-2626 - Pima Air & Space Museum, adjacent to Davis-Monthan AFB in Tucson, Arizona.
- KC-97L 52-2630 - National Museum of the United States Air Force, Wright-Patterson Air Force Base, Dayton, Ohio. 
- C-97G 52-2764 - at the Don Q Inn, next to the (now closed) Dodgeville Municipal Airport outside Dodgeville, Wisconsin. It was used for filming commercials and has a fuselage signed by Farrah Fawcett
- C-97G 53-218 - At the Minnesota Air Guard Museum on the north side of the Minneapolis - St. Paul International Airport since 3 November, 2000. Formerly owned by Hawkins and Powers, Greybull, WY.
- C-97? - At the Cleveland I-X Center grounds in Cleveland Ohio. Formerly flown by the Ohio National Guard. 
- Crew: 5–6 (Pilot, Copilot, Navigator, Flight engineer, 1–2 Loadmasters)
- 134 troops or
- 69 stretchers or
- tanker equipment
- Length: 110 ft 4 in (33.7 m)
- Wingspan: 141 ft 3 in (43.1 m)
- Height: 38 ft 3 in (11.7 m)
- Wing area: 1,734 ft² (161.1 m²)
- Empty weight: 82,500 lb (37,410 kg)
- Useful load: 37,500 lb (17,010 kg)
- Loaded weight: 120,000 lb (54,420 kg)
- Max. takeoff weight: 175,000 lb (79,370 kg)
- Powerplant: 4 × Pratt & Whitney R-4360B Wasp Major radial engines, 3,500 hp (2,610 kW) 28-cylinders each
- Maximum speed: 375 mph (603 km/h)
- Cruise speed: 260 knots (300 mph, 482 km/h)
- Range: 4,949 mi (4,300 nm, 6,920 km)
- Ferry range: 5,000 nm (5,760 mi, 9,270 km)
- Service ceiling: 35,000 ft (10,670 m)
- Wing loading: 69.2 lb/ft² (337.8 kg/m²)
- Power/mass: 0.117 hp/lb (192 W/kg)
- Aero Spacelines Mini Guppy
- Aero Spacelines Pregnant Guppy
- Aero Spacelines Super Guppy
- Boeing 377 Stratocruiser
- Boeing B-50 Superfortress
- Boeing KC-97 Stratofreighter
Aircraft of comparable role, configuration and era
- Convair XC-99
- Douglas C-54 Skymaster
- Douglas C-118 Liftmaster
- Douglas C-124 Globemaster II
- Lockheed C-69 Constellation
- Lockheed C-121 Constellation
- Lockheed C-130 Hercules
- Lockheed R7V-2/YC-121F Constellation
- Bach 1996, p. 7
- Bowers 1989, pp. 353–359.
- Swanborough and Bowers 1989, p. 125.
- Bowers 1989, p. 353.
- Bach 1996, p. 40
- "ASN Aviation Safety Database." Aviation Safety Network, Flight Safety Foundation. Retrieved: 27 April 2009.
- Archer Aeroplane May 2017, p. 94.
- Rubinstein and Goldman 1979, p. 89.
- "East of the Suez". Israeli Air Force official website. Retrieved 19 February 2013.
- Bowers 1989, p. 357.
- Bowers 1989, p. 358.
- Bowers 1989, p. 362.
- Bowers 1989, p. 364.
- Ravenstein, Charles A., ed. Air Force Combat Wings: Lineage and Honors Histories, 1947–1977. Washington, D.C.: United States Air Force Historical Research Center, Office of Air Force History, 1984. ISBN 0-912799-12-9.
- "A Mission of History, Education and Remembrance." Spirit of Freedom, 2011. Retrieved: 21 October 2011.
- Accident description for 43-27472 at the Aviation Safety Network. Retrieved on 26 January 2013.
- Accident description for 48-0398 at the Aviation Safety Network. Retrieved on 26 January 2013.
- Union News, Springfield, Massachusetts, 16 October 1951.
- Accident description for 48-0413 at the Aviation Safety Network. Retrieved on 26 January 2013.
- Accident description for 52-2654 at the Aviation Safety Network. Retrieved on 2015-06-30.
- Accident description for 53-0110 at the Aviation Safety Network. Retrieved on 2015-06-30.
- Accident description for 51-0220 at the Aviation Safety Network. Retrieved on 2015-06-30.
- Accident description for 52-0222 at the Aviation Safety Network. Retrieved on 2015-06-30.
- Accident description for 50-0702 at the Aviation Safety Network. Retrieved on 26 January 2013.
- Accident description for 52-2737 at the Aviation Safety Network. Retrieved on 2015-06-30.
- Accident description for 52-2711 at the Aviation Safety Network. Retrieved on 2015-06-30.
- Accident description for 49-2597 at the Aviation Safety Network. Retrieved on 26 January 2013.
- Accident description for 52-2703 at the Aviation Safety Network. Retrieved on 2015-06-30.
- Accident description for 51-0363 at the Aviation Safety Network. Retrieved on 2015-06-30.
- Accident description for 52-2738 at the Aviation Safety Network. Retrieved on 2015-06-30.
- Accident description for 52-2773 at the Aviation Safety Network. Retrieved on 2015-06-30.
- Accident description for 52-907 at the Aviation Safety Network. Retrieved on 2015-06-30.
- Accident description for 52-0904 at the Aviation Safety Network. Retrieved on 2025-06-30.
- Accident description for N52676 at the Aviation Safety Network. Retrieved on 26 January 2013.
- Accident description for 4X-FPS/037 at the Aviation Safety Network. Retrieved on 2015-06-30.
- Accident description for 4X-FPR/033 at the Aviation Safety Network. Retrieved on 2015-06-30.
- "Accident Report: Boeing C-97 Stratofreighter G, 30 July 1987." Aviation Safety Network. Retrieved: 21 October 2011.
- "C-97K Stratofreighter/AF Serial No. 52-2799." aeroflight.co.uk. Retrieved: 8 November 2011.
- "FAA Registry: N117GA." faa.gov Retrieved: 20 July 2016.
- "C-97G Stratofreighter/AF Serial No. 52-2718 'Angel of Deliverance'." spiritoffreedom.org. Retrieved: 13 November 2010.
- "USAF Serial Number Search (52-898)". Retrieved 2018-02-14.
- "Aerial Visuals Airframe Dossier (52-0898)". Retrieved 2018-02-14.
- "C-97G Stratofreighter/AF Serial No. 52-2626." pimaair.org. Retrieved: 20 July 2016.
- "C-97G Stratofreighter/AF Serial No. 52-2764." Don Q Inn. Retrieved: 20 July 2016.
- "Boeing – History – C-97 Stratofreighter." Archived 2010-02-07 at the Wayback Machine Boeing. Retrieved: 27 April 2009.
- Hansen, Dave. "Boeing C-97 Stratofreighter." Warbird Alley, 27 April 2009.
- "C-97 Stratofreighter Specifications." GlobalSecurity.org, 27 April 2009.
- Bridgman 1952, p. 184.
- Archer, Bob. "Database: Boeing C-97". Aeroplane, Vol. 45, No. 5, May 2017. pp. 81–97. ISSN 0143-7240.
- Bach, Martin. Boeing 367 Stratofreighter, Boeing 377 Stratocruiser, Aero Spacelines Guppies. Allershausen: NARA Verlag, 1996. ISBN 3-925671-18-8.
- Bowers, Peter M. Boeing Aircraft since 1916. London: Putnam Aeronautical Books, 1989, ISBN 0-85177-804-6.
- Bridgman, Leonard. Jane's All The World's Aircraft 1952–53. London: Sampson Low, Marston & Company, 1952.
- Rubinstein, Murray and Richard Goldman. The Israeli Air Force Story London: Arms & Armour Press, 1979. ISBN 0-85368-462-6.
- Swanborough, Gordon and Peter M Bowers: United States Military Aircraft since 1909. London: Putnam Aeronautical Books, 1989, ISBN 0-85177-816-X.
|Wikimedia Commons has media related to Boeing C-97 Stratofreighter.|
- How to Fly the C97
- Airliners.net – The Boeing C-97 Stratofreighter
- Angel of deliverance: Boeing C-97G sn 52-2718
- Goleta Air & Space Museum – Boeing C-97 Stratofreighter/Stratotanker
- PhotoValet – Air Force Military Aircraft: Boeing C-97 and KC-97 Stratotanker/Stratofreighter images
- Newsreel introducing the C97 showing rear ramp