Boeing C-97 Stratofreighter

1st Flight 1944

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.

The prototype XC-97 was powered by the 2,200 hp (1,600 kW) Wright R-3350 engine, the same as used in the B-29.

The XC-97 took off for its first flight on November 9, 1944.

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 take-offs 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.

Variants

XC-97

Military designation of the prototype Boeing 367.

YC-97

Cargo transport.

YC-97A

Troop carrier.

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.

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.

C-97F

KC-97Fs converted to transports.

KC-97F

3800hp R-4360-59B engines and minor changes.

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 under wing fuel tanks.

GKC-97G

Five KC-97Gs were used as ground instruction airframes.

JKC-97G

One aircraft was modified to test the under wing General Electric J47-GE-23 jet engines, and was later designated KC-97L.

HC-97G

KC-97Gs converted for search and rescue operations.

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 under wing pylons.

Specifications

C-97

Crew

5–6

Capacity

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 take-off 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

Performance

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).

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