C-97F Stratofreighter

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.Bach 1996, p. 7 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 a second lobe on top of the fuselage and wings of the B-29 Superfortress with the tail, wing, and engine layout being nearly identical.Swanborough and Bowers 1989, p. 125. The XC-97 and YC-97 can be distinguished from the Boeing 377 Stratocruiser and later C-97s by the shorter fin, and later ones by the flying boom and jet engines on the tanker models.

The prototype XC-97 was powered by the same Wright R-3350 engines as used in the B-29. The XC-97 took off for its first flight on November 9, 1944, just after the death of Boeing president Philip G. Johnson.

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 with of cargo. The tenth and all subsequent aircraft were fitted with the Pratt & Whitney Wasp Major engines and 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 but was not a combat transport able to deliver to primitive forward bases. The doors could not be opened in flight, but could be removed to carry out air drops. The C-97 had a useful payload of , which could include two 2½-ton trucks, towed artillery, or light tracked vehicles such as the M56 Scorpion. The C-97 featured cabin pressurization, which made long flights more comfortable.

The C-97 was developed into the civilian Boeing 377 Stratocruiser, a transoceanic airliner that could be fitted with sleeper cabins and featured a lower deck lounge. The first Stratocruiser flew on July 8, 1947. Only 56 were built.Bach 1996, p. 40

Operational history

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, (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.Archer ''Aeroplane'' May 2017, p. 94. 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.

Variants

;XC-97: military designation of the prototype Boeing 367, three built.
;YC-97: cargo transport, six built.

;YC-97A: troop carrier, three built.
;YC-97B: fitted with 80 airliner-style seats, later redesignated C-97B, in 1954 became C-97D, retired to MASDC 15 December 1969.
;C-97A: transport, 50 built.
;KC-97A: 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.
;C-97C: Second production version, 14 built; those used as medical evacuation transports during the Korean War were designated MC-97C.
;VC-97D: staff transport and flying command post conversions, three C-97As converted.
;C-97E: KC-97Es converted to transports.
;KC-97E
: aerial refueling tankers with rear loading doors permanently closed; 60 built.
;C-97F: KC-97Fs converted to transports.
;KC-97F
: 3800hp R-4360-59B engines and minor changes; 159 built.
;C-97G: 135 KC-97Gs converted to transports.
;EC-97G: ELINT conversion of three KC-97Gs. 53–106 was operated by the CIA for covert ELINT operations in the West Berlin Air Corridor.
;KC-97G
: dual-role aerial refueling tankers/cargo transportation aircraft. KC-97G models carried underwing fuel tanks; 592 built.
;GKC-97G
:Five KC-97Gs were used as ground instruction airframes.
;JKC-97G
:One aircraft was modified to test the underwing General Electric J47-GE-23 jet engines, and was later designated KC-97L.
;HC-97G: KC-97Gs converted for search and rescue operations; 22 converted.
;KC-97H

:One KC-97F was experimentally converted into a probe-and-drogue refueling aircraft.
;YC-97J: KC-97G conversion with four 5,700 hp (4,250 kW) Pratt & Whitney YT34-P-5 turboprops, two converted. Originally designated YC-137.
;C-97K: 27 KC-97Gs converted to troop transports.
;KC-97L
:81 KC-97Gs modified with two J47 turbojet engines on underwing pylons.

Operators

Military operators

;
* Israeli Air Force
;
*Spanish Air Force
;
* United States Air Force

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

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