The Lockheed XC-35

The Lockheed XC-35 was a twin-engine, experimental pressurized airplane. It was the first American aircraft to feature cabin pressurization. The distinction of the world's first pressurized aircraft goes to the Junkers Ju 49. The XC-35 was a development of the Lockheed L-10 Electra that was designed per a 1935 request by the United States Army Air Corps for an aircraft with a pressurized cabin.

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 10 hours with at least 2 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 in Ohio were responsible for the design of the pressurized cabin structure. Greene and Younger worked with Lockheed to modify a L-10 Electra with a new fuselage consisting a circular cross section that was able to withstand up to a 10 psi differential. 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.  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).  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 accommodations for one passenger and could only be used 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 L-10 Electra. The engines featured a turbo supercharger to permit the engines to operate in the thin air at high altitudes.

The XC-35 was fitted with a pair of Pratt & Whitney XR-1340 radial engines. These 550-hp engines were turbo-supercharged to deliver the necessary high-altitude performance. The plane was designed to fly at altitudes above 30,000 feet.

XC-35



Lockheed XC-35 Role Experimental National origin United States Manufacturer Lockheed First flight 9 May 1937 Introduced 1937 Status In storage at the Smithsonian Institution's National Air and Space Museum Primary user United States Army Air Corps Number built 1 Developed from Lockheed L-10 Electra

XC-35
Lockheed XC-35
Role	Experimental
National origin	United States
Manufacturer	Lockheed
First flight	9 May 1937
Introduced	1937
Status	In storage at the Smithsonian Institution's National Air and Space Museum
Primary user	United States Army Air Corps
Number built	1
Developed from	Lockheed L-10 Electra

General characteristics

• Crew: 3
• Capacity: 6
• Length: 38 ft 7 in (11.8 m)
• Wingspan: 55 ft 0 in (16.8 m)
• Height: 10 ft 1 in (3.1 m)
• Wing area: 458 ft (42.6 m)
• Loaded weight: 10,500 lb (4,760 kg)
• Max takeoff weight: lb (kg)
• Powerplant: 2× Pratt & Whitney R-1340-43, 550 hp (410 kW) each

Performance

• Maximum speed: 236 mph (380 km/h)
• Range: 800 mi (1,285 km)
• Service ceiling: 31,500 ft (9600 m)
• Wing loading: 22.9 lb/ft² (111.7 kg/m²)