Boeing C-75: Wikis

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C-75 Stratoliner
Converted TWA Stratoliner Cherokee Begins Wartime Transatlantic Duty
Role Long-range transport
Manufacturer Boeing
Introduced 1942
Primary user United States Army Air Forces
Number built 5
Developed from Boeing 307

The Boeing C-75 was a long-range transport aircraft operated during World War II, introduced early in 1942. It was used exclusively by the United States Army Air Forces's Air Transport Command, and pioneered transatlantic air travel by commercial landplane.

The aircraft was a modified Boeing 307. The modifications were made to give the transport the range needed for transatlantic flights with a useful payload of VIPs or cargo. It had two main routes, New York to Scotland, and Washington D.C. to Cairo. During the flight, a stop at Greenland, Iceland, or Ascension Island could be made.

After the war, the five aircraft were returned to TWA, restored by Boeing with new B-17G Flying Fortress wings and engines, and B-29-type electronics.[1]

Contents

Development

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Background

At the time the US entered WW2 in December 1941, flying across the oceans was a rare luxury. But the war required government and military officials to travel across the oceans, and most of the four-engined commercial long-range aircraft were put to this use: Pan Am's 14 flying boats and TWA's 5 Boeing 307 landplanes. Additional fuel tanks were added to the 307's to give them the extra range required. The converted 307's were designated C-75 by the military. Before WW2 ended their production, ten Boeing 307 commercial transports, named Stratoliners, had been built. TWA bought five and flew domestic routes between New York and Los Angeles for 18 months until the Army purchased them following the Japanese attack on Pearl Harbor. The intended wartime use was long-range transatlantic flight with a payload of VIPs or critical cargo. TWA converted their five Stratoliners for military service in January 1942,[2] and its Intercontinental Division (ICD) then operated these C-75's under contract to the Army's Air Transport Command (ATC) until July 1944.[1] These were the only commercial landplanes able to cross the Atlantic with a payload until the arrival of the C-54 Skymaster in November 1942.

Conversion

The Boeing 307 was based on the B-17C with a different fuselage of circular cross section 138 inches (3.51 m) in diameter.[1] Conversion to C-75 included removal of the pressurization equipment to save weight, removal of the forward (four or) five of nine reclining seats along the port side, and alteration of the two forward Pullman-like compartments (of four) starboard of the left-of-centerline aisle. Space was thus provided for crew requirements on extremely long flights and for the addition of five 212.5 U.S. gallon (804 L) fuel tanks. The landing gear was strengthened, the maximum take-off weight was increased from 45,000 lb to 56,000 lb (from 20,400 to 25,400 kg), and the exterior was painted olive drab.[1]

Operational history

Transatlantic routes

Converted TWA Stratoliner Apache first to land at Bluie West Eight on Greenland's west coast, April 20, 1942. Otis Bryan, ICD Head, second from left. It is 20 degrees below zero Fahrenheit (−30 °C).

Two main routes were flown: Washington, DC to Cairo across the South Atlantic, and New York to Scotland across the North Atlantic.[3] They often flew non-stop the 2,125 statute miles (3,415 km) between Gander, Newfoundland and Prestwick, Scotland in the north, and the 2,550 statute miles (4,100 km) between Natal, Brazil and Accra, Ghana in the south. These were very long flights for the time. After July 1942, a refueling stop at Ascension Island was an option in the south.[4] In the north, stops at Iceland or Greenland were often necessary, especially flying westbound against the prevailing winds. As C-54's took over the Gander to Prestwick route, the C-75's operated a Marrakech to Prestwick service out over the Atlantic.[3]

Noteworthy flights

On February 26, 1942, Otis Bryan, head of the ICD, piloted Navajo to survey the route from Washington, DC to Cairo across the South Atlantic, and to deliver armor-piercing shells for British artillery in use against the Afrika Korps.[5] In March 1942, Bryan was asked by General Arnold to pilot the top brass, including Generals Marshall, Eisenhower, Clark, Col. Vandenberg, Admiral Towers, Averill Harriman, and Harry Hopkins, across the North Atlantic to England.[1] In May a similar all-brass flight was made by Apache, displaying remarkable confidence in the C-75.[1] In June, 1942, Comanche made 20 crossings shuttling across the South Atlantic between Natal and West Africa spending 384 hours in the air and carrying a total of 229 passengers and 53,000 lb (24,0000 kg) of cargo.[6] Jimmy Doolittle and others from the Doolittle Raid returned to the US in a C-75. TWA and the C-75 were making transatlantic crossing by landplane routine. "Before the C-75's were returned to their private owners, they completed some 3,000 ocean crossings and logged more than 45,000 hours in flying to every corner of the world."[7]

After the war

In April, 1945 the five aircraft were returned to TWA, having been restored by Boeing and recertified by the CAA as SA-307B-1 civilian transports with their old registration numbers. The restoration included new B-17G Flying Fortress wings and engines, horizontal stabilizer moved three feet (0.9 m) aft, and B-29-type electronics. TWA then restyled the interior cabin in two sections, 10 seats forward and 28 aft.[1]

Individual aircraft

TWA Name Boeing Construction Number USAAF Serial Number Civil Registration Number
Cherokee 1998 42-88623 NC 19906
Comanche 1996 42-88624 NC 19905
Zuni 1999 42-88625 NC 19907
Apache 2000 42-88626 NC 19908
Navajo 2001 42-88627 NC 19909

Operators

 United States

Specifications (C-75)

General characteristics

  • Crew: 8-10: Pilots (2), 1st Officer (1), 2nd Officer (1 sometimes), Navigators (2), Flight Radio Officers (2), Flight Engineer (1), Purser (1 if passengers)
  • Capacity: 12 passengers long range, 16 passengers short range
  • Length: 74 ft 4 in (22.66 m)
  • Wingspan: 107 ft 3 in (32.69 m)
  • Height: 20 ft 9 in (6.32 m)
  • Wing area: 1,486 ft² (138.1 m²)
  • Empty weight: approx. 30,300 lb (13,700 kg)
  • Max takeoff weight: 56,000 lb (25,400 kg)
  • Powerplant:Wright R-1820-G105A Cyclone radials, 1,100 hp (820 kW) each
  • Fuel capacity: 2,760 US gal (10,450 L) (1,700 gal/6,440 L in wing tanks plus 1,060 gal/4,010 L in fuselage tanks)

Performance

  • Maximum speed: 246 mph at 17,300 ft (396 km/h at 5,300 m)
  • Cruise speed: 220 mph at 15,700 ft (354 km/h at 4,800 m)
  • Range: 2,700 statute miles with payload (4,350 km)
  • Service ceiling: 26,200 ft (8,000 m)
  • Normal cruising altitude: 1,000–9,000 ft (300–2,700 m)

See also

Related development

Comparable aircraft

References

  1. ^ a b c d e f g Betts, Ed (1993). "The Boeing Stratoliners and TWA". American Aviation Historical Society Journal 38 (3).  
  2. ^ Jane's Fighting Aircraft of World War II. London: Random House. 1989. ISBN 1 85170 199 0.  
  3. ^ a b Berry, Peter (1995). "Transatlantic Flight 1938-1945 (Part I 1938-1943)". AAHS Journal 40 (2).  
  4. ^ Berry, Peter (1995.). "Transatlantic Flight 1938-1945 (Part II 1943-1945)". AAHS Journal 40 (3).  
  5. ^ Davies (2000). TWa: An Airline and Its Aircraft. McLean, Virginia: Paladwr Press. ISBN 1-888962-16-X.  
  6. ^ Cleveland, Reginald M. (1946). Air Transport At War. New York & London: Harper & Brothers.  
  7. ^ Bauer, Eugene E. (1990). Boeing in Peace and War. Enumclaw, Washington: TABA Publishing.  

Bibliography

  • Betts, Ed, "The Boeing 'Stratoliner' (1935 through 1940)" Part 1 of 2, TARPA TOPICS, August 1990. (TWA Active Retired Pilots Association magazine).
  • Betts, Ed, "The Boeing 'Stratoliner' (1935 through 1940)" Part 2 of 2, TARPA TOPICS, August, 1994.
  • Betts, Ed, "The Intercontinental Division" (Part 1 of 3), TARPA TOPICS.
  • Betts, Ed, "The ICD Story Part Two: The Year 1943" (Part 2 of 3), TARPA TOPICS, February, 1994.
  • Betts, Ed, "The Intercontinental Division (ICD) 1944-1946 Part III", (Part 3 of 3), TARPA TOPICS.
  • Davies, R. E. G., Airlines of the United States Since 1914 (Wash D.C.:Smithsonian Institution Press, 1998). ISBN 1-888962-08-9.
  • "Boeing 307 Stratoliner: The World's First High-Altitude Airliner", Boeing Historical Archives, 1989.

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