The Lockheed XC-35 is a twin-engine, experimental pressurized airplane. It was the second American aircraft to feature cabin pressurization. It was initially described as a "supercharged cabins" by the Army. The XC-35 was a development of the

Lockheed Model 10 Electra The Lockheed Model 10 Electra is an American twin-engined, all-metal monoplane airliner developed by the Lockheed Aircraft Corporation in the 1930s to compete with the Boeing 247 and Douglas DC-2. The type gained considerable fame as one was f ...

that was designed to meet a 1935 request by the

United States Army Air Corps The United States Army Air Corps (USAAC) was the aerial warfare service component of the United States Army between 1926 and 1941. After World War I, as early aviation became an increasingly important part of modern warfare, a philosophical r ...

for an aircraft with a

pressurized cabin Cabin pressurization is a process in which conditioned air is pumped into the cabin of an aircraft or spacecraft in order to create a safe and comfortable environment for passengers and crew flying at high altitudes. For aircraft, this air is u ...

.Lockheed XC-35 Electra
Smithsonian Institution National Air and Space Museum.

Design and development

The United States Air Corps wanted the aircraft to perform high altitude research and to test the feasibility of a pressurized cabin. The Corps contracted with Lockheed Aircraft Corporation to produce the aircraft at a total cost of $112,197. The requirements called for an aircraft capable of flying at no less than 25,000 ft (7,620 m) and having an endurance of ten hours with at least two hours above 25,000 ft (7,620 m). Major Carl Greene and John Younger, both structures experts who worked for the Air Corps Engineering Division at

Wright Field Wilbur Wright Field was a military installation and an airfield used as a World War I pilot, mechanic, and armorer training facility and, under different designations, conducted United States Army Air Corps and Air Forces flight testing. Lo ...

in Ohio were responsible for the design of the pressurized cabin structure. Greene and Younger worked with Lockheed to modify a Model 10 Electra with a new fuselage consisting of a circular cross-section that was able to withstand up to a 10 psi differential.Lockheed XC-35
, National Museum of the Air Force. New, smaller windows were used to prevent a possible blowout while operating at high pressure differentials. The cabin pressurization was provided by bleeding air from the engines' turbo supercharger, the compressor outlet fed into the cabin and was controlled by the flight engineer.Airplanes that Transformed Aviation
Air & Space Magazine. This system was able to maintain a cabin altitude of 12,000 ft (3,658 m) while flying at 30,000 ft (9,144 m).Van Patten, Robert E.
Air Force Magazine Online, Vol.86, No.1 January 2003 The fuselage was divided into two compartments, a forward pressurized compartment, and an aft unpressurized compartment. The forward compartment housed two pilots, a flight engineer, and up to two passengers. The aft compartment provided accommodation for one passenger and could be used only at low altitudes since it lacked pressurization. The XC-35 was fitted with two Pratt & Whitney XR-1340-43 engines of 550 hp (410 kW) each compared to the two Pratt & Whitney R-985-13 of 450 hp (336 kW) fitted to the base Model 10 Electra. The engines featured a turbo supercharger to permit the engines to operate in thin air at high altitudes.

Operational history

The XC-35 was delivered to Wright Field, Ohio in May 1937, made its first performance flight on August 5, and was involved in an extensive flight testing program for which the Army Air Corps was awarded the Collier Trophy. The lessons learned from the XC-35 played a key role in the development of the

Boeing 307 Stratoliner The Boeing Model 307 Stratoliner (or Strato-Clipper in Pan American service, or C-75 in USAAF service) is an American stressed-skin four-engine low-wing tailwheel monoplane airliner derived from the B-17 Flying Fortress bomber, which entered co ...

and the

B-29 Superfortress The Boeing B-29 Superfortress is an American four-engined propeller-driven heavy bomber, designed by Boeing and flown primarily by the United States during World War II and the Korean War. Named in allusion to its predecessor, the B-17 F ...

which was to be the first mass-produced pressurized aircraft. The Air Corps brass were so confident in the new technology that they allowed the XC-35 to be used as an executive transport for Louis Johnson, the Assistant

Secretary of War The secretary of war was a member of the U.S. president's Cabinet, beginning with George Washington's administration. A similar position, called either "Secretary at War" or "Secretary of War", had been appointed to serve the Congress of the ...

and future Secretary of Defense. In 1943,

NACA The National Advisory Committee for Aeronautics (NACA) was a United States federal agency founded on March 3, 1915, to undertake, promote, and institutionalize aeronautical research. On October 1, 1958, the agency was dissolved and its assets ...

pilot Herbert H. Hoover flew the XC-35 into

thunderstorms A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are somet ...

to gather data on the effects of severe weather on aircraft in flight.Herbert H. Hoover & Lockheed XC-35
NASA Image eXchange Collection The XC-35 was donated to the

Smithsonian Institution The Smithsonian Institution ( ), or simply the Smithsonian, is a group of museums and education and research centers, the largest such complex in the world, created by the U.S. government "for the increase and diffusion of knowledge". Founded ...

's National Air and Space Museum in 1948 and remains there in long term storage.

Specifications (Lockheed XC-35)

References

External links

XC-35 in the collection of the National Air and Space Museum

XC-35 from National Museum of the United States Air Force

XC-35 Photo Gallery
from National Museum of the United States Air Force {{USAF transports C-035 1930s United States experimental aircraft 1930s United States military transport aircraft Low-wing aircraft World War II transport aircraft of the United States Aircraft first flown in 1937 Twin piston-engined tractor aircraft

Design and development

Operational history

Specifications (Lockheed XC-35)

See also

References

External links