Boeing C-75

Infobox Aircraft
name = C-75 Stratoliner
type = Long-range transport
manufacturer = Boeing

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caption = Converted TWA Stratoliner "Cherokee" Begins Wartime Transatlantic Duty
designer =
first flight =
introduced = 1942
retired =
status =
primary user = United States Army
more users =
produced =
number built = 5
unit cost =
developed from = Boeing 307
variants with their own articles =

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.

Background

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 the spring of 1942, and its Intercontinental Division (ICD) then operated these C-75's under contract to the Army's Air Transport Command (ATC) until July 1944. [Betts, Ed: "The Boeing Stratoliners and TWA", "American Aviation Historical Society Journal", Vol 38 Number 3, Fall 1993, pp. 167-183. Photos by permission of Betts Collection] 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 (Betts 1993:167). 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 (Betts 1993:172).

Transatlantic routes

Two main routes were flown: Washington, DC to Cairo across the South Atlantic, and New York to Scotland across the North Atlantic. [Berry, Peter, "Transatlantic Flight 1938-1945 (Part I 1938-1943)","AAHS Journal" Vol 40 Number 2, Summer 1995, pp.145-146.] 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 (Berry 1995:147). 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 (Berry 1995:147).

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. [Davies, R. E. G., "TWA: An Airline and Its Aircraft" (McLean, Virginia: Paladwr Press, 2000), pp.45,46. ISBN 1-888962-16-X.] 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 (Betts: 1993:174). In May a similar all-brass flight was made by "Apache", displaying remarkable confidence in the C-75 (Betts 1993:175). 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. [Cleveland, Reginald M.,"Air Transport At War" (New York & London: Harper & Brothers Publishers, 1946), p.276.] 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." [Bauer, Eugene E., "Boeing in Peace and War" (Enumclaw, Washington:TABA Publishing, 1990), p.116.]

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. [Betts 1993, p.179.]

urvivors

"Flying Cloud", the only surviving Stratoliner and one of three Model S-307's operated by Pan American Airways, is on display at the Smithsonian's Steven F. Udvar-Hazy Center. During the war, "Pan Am's three Stratoliners remained their property and arrangements were made for the airline to fly their Latin American routes under the [Air Transport Command's] direction" (Betts 1993:172).

C-75 Transports by name and number

pecifications (C-75)

aircraft specifications

plane or copter?=plane
jet or prop?=prop

ref=

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
payload main=
payload alt=
length main=74 ft 4 in
length alt=22.66 m
span main=107 ft 3 in
span alt=32.69 m
height main=20 ft 9 in
height alt=6.32 m
area main= 1,486 ft²
area alt= 138.1 m²
airfoil=
empty weight main=approx. 30,300 lb
empty weight alt= 13,700 kg
loaded weight main=
loaded weight alt=
useful load main=
useful load alt=
max takeoff weight main=56,000 lb
max takeoff weight alt= 25,400 kg
more general=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)

engine (jet)=
type of jet=
number of jets=
thrust main=
thrust alt=
thrust original=
afterburning thrust main=
afterburning thrust alt=
engine (prop)=
type of prop=Wright R-1820-G105A Cyclone radials
number of props=4
power main=1,100 hp
power alt=820 kW
power original=

max speed main=246 mph at 17,300 ft
max speed alt= 396 km/h at 5,300 m
cruise speed main=220 mph at 15,700 ft
cruise speed alt= 354 km/h at 4,800 m
stall speed main=
stall speed alt=
never exceed speed main=
never exceed speed alt=
range main=2,700 statute miles with payload
range alt=4,350 km
ceiling main=26,200 ft
ceiling alt= 8,000 m
climb rate main=
climb rate alt=
loading main=
loading alt=
thrust/weight=
power/mass main=
power/mass alt=
more performance=*Normal cruising altitude: 1,000–9,000 ft (300–2,700 m)
*Long-range cruise speed: 140 mph (225 km/h) IAS [Buck, Bob, TWA pilot and author, personal correspondence]
armament=
avionics=

References

*Berry, Peter, "Transatlantic Flight 1938-1945 (Part II 1943-1945)", "AAHS Journal" Vol 40, Number 3, Fall 1995.
*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.

ee also

aircontent
related=
* B-17 Flying Fortress
* Boeing 307

similar aircraft=
* Douglas DC-4

sequence=
* 294 - 299 - 300 - 307 - 314 - 316 - 345
lists=
see also=