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
The Boeing C-97 Stratofreighter was a long-range heavy military cargo aircraft developed from the B-29 and B-50 bombers. Design work began in 1942, the first of three prototype XC-97s flew on 9 November 1944 (none saw combat), and the first of six service-test YC-97s flew on 11 March 1947. All nine were based on the 24ST alloy structure and Wright R-3350 engines of the B-29, but with a larger-diameter fuselage upper lobe (making a figure of eight or "double-bubble" section) and they had the B-29 vertical tail with the gunner's position blanked off. The first of three heavily revised YC-97A incorporating the re-engineered wing ( higher strength 75ST alloy), taller vertical tail and larger Pratt and Whitney R-4360 engines of the B-50 bomber, flew on 28 January 1948 and was the basis of the subsequent sole YC-97B, all production C-97s, KC-97s and civilian Stratocruiser aircraft. Between 1944 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).
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 that 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 Boeing 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, D.C. 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 two retractable ramps could be used to drive in cargo. However, unlike the later Lockheed C-130 Hercules, it was not designed as a combat transport that could deliver directly to primitive forward bases using relatively short takeoffs and landings. The two rear ramps could not be used in flight; but removed, the C-97 could be used 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 that 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 Douglas 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 to 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 Boeing KC-135 Stratotanker in 1957. Many KC-97s were later refitted as C-97G transports and equipped several squadrons of the U.S. 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,[when?] (S/N 52-2718, named "Angel of Deliverance") operated by the Berlin Airlift Historical Foundation. It is painted as YC-97A 45-59595, the only 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 ramps. 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. Originally designated YC-137.
- 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 from Lajes AFB (LFB), Azores 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.
- 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.
- 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. The navy confirmed that debris found 277 miles to the southwest of Honolulu, was wreckage of the plane.
- 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.
- 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 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 (converted from KC-97G)
- 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 (all converted from KC-97G)
- 52-2626 – Pima Air & Space Museum, adjacent to Davis–Monthan Air Force Base in Tucson, Arizona.
- 52-2764 – Don Q Inn, next to the (now closed) Dodgeville Municipal Airport outside Dodgeville, Wisconsin. It was used for filming commercials and its fuselage was signed by Farrah Fawcett
- 53-218 – Minnesota Air Guard Museum on the north side of the Minneapolis – St. Paul International Airport since 3 November 2000.
- Crew: 5–6 (Pilot, Copilot, Navigator, Flight engineer, 1–2 Loadmasters)
- 134 troops or
- 69 stretchers or
- refuelling boom (three KC-97A aircraft only)
- Length: 110 ft 4 in (33.63 m)
- Wingspan: 141 ft 3 in (43.05 m)
- Height: 38 ft 3 in (11.66 m)
- Wing area: 1,734 sq ft (161.1 m2)
- Airfoil: root: Boeing 117 (22%) ; tip: Boeing 117 (9%)
- Empty weight: 82,500 lb (37,421 kg)
- Gross weight: 120,000 lb (54,431 kg)
- Max takeoff weight: 175,000 lb (79,379 kg)
- Powerplant: 4 × Pratt & Whitney R-4360B Wasp Major 28-cylinder air-cooled radial piston engines, 3,500 hp (2,600 kW) each
- Propellers: 4-bladed Hamilton Standard constant-speed fully-feathering propellers
- Maximum speed: 375 mph (604 km/h, 326 kn)
- Cruise speed: 300 mph (480 km/h, 260 kn)
- Range: 4,300 mi (6,900 km, 3,700 nmi)
- Ferry range: 5,760 mi (9,270 km, 5,010 nmi)
- Service ceiling: 35,000 ft (11,000 m)
- Wing loading: 69.2 lb/sq ft (338 kg/m2)
- Power/mass: 0.117 hp/lb (0.192 kW/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 49-2602 at the Aviation Safety Network. Retrieved on 18 June 2020.
- Accident description for 48-0413 at the Aviation Safety Network. Retrieved on 26 January 2013.
- Accident description for 50-0702 at the Aviation Safety Network. Retrieved on 26 January 2013.
- Accident description for 49-2597 at the Aviation Safety Network. Retrieved on 26 January 2013.
- Accident description for 52-2773 at the Aviation Safety Network. Retrieved on 2015-06-30.
- Accident description for N52676 at the Aviation Safety Network. Retrieved on 26 January 2013.
- "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: 28 October 2020.
- "C-97G Stratofreighter/AF Serial No. 52-2718 'Angel of Deliverance'." spiritoffreedom.org. Retrieved: 13 November 2010.
- "C-97G Stratofreighter/AF Serial No. 52-2626." pimaair.org. Retrieved: 5 November 2019.
- "C-97G Stratofreighter/AF Serial No. 52-2764." Don Q Inn. Retrieved: 20 July 2016.
- "C-97G Stratofreighter/AF Serial No. 53-218." Minnesota Air Guard Museum. Retrieved: 5 November 2019.
- "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.
- Lednicer, David. "The Incomplete Guide to Airfoil Usage". m-selig.ae.illinois.edu. Retrieved 16 April 2019.
- 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 ramps