By 1942, the United States had joined the Allied side and had become an important rear industrial production base, but the continental United States was far from the front line of the war, separated by the Atlantic and Pacific Oceans on both sides, especially the sea routes in Europe, where there were a large number of elusive U-boats, and their wolf pack tactics caused great losses to merchant ships.
In this case, the United States began to pay attention to long-distance transport aircraft that can cross oceans, although its transportation capacity cannot be compared with that of merchant ships, but the air routes are safer, and the transportation speed is much faster, suitable for transporting important people or goods.
After Pearl Harbor, the United States officially participated in World War II, and began to mobilize the country's industry to fully devote itself to the development and production of weapons, including Lockheed Aircraft Corporation, when the company's L-049 "Constellation" passenger aircraft was requisitioned and converted into military transport aircraft, a total of 22 were produced during World War II (7 of which were not yet delivered), and the aircraft received a new designation C-69.
As a large 4-engine long-range transport aircraft, the C-69 served the U.S. Army and Air Force, and the military livery was changed, and the military was recognized for its excellent performance, and some aircraft were converted into passenger planes after World War II to continue to be used.
The performance of the C-69 transport aircraft is directly proportional to its appearance, the aircraft adopts a low monowing layout, the fuselage is slender and smooth like the fuselage of a high-speed fighter, the front three-point landing gear can lift the fuselage high off the ground, it is a "big long leg", and the tail of the aircraft is installed on the flat tail with three vertical tails.
The aircraft uses four Wright R-3350-35 18-cylinder air-cooled radial piston engines, each with an output of 2,200 horsepower, each driving a pair of three-blade constant-speed propellers, which can make this large aircraft reach a maximum flight speed of 530 km/h, which is already comparable to some fighter models in the early stage of World War II.
The pilot has a hydraulically controlled flight control equipment that can fly this large aircraft with relative ease, a total of 12 flaps are installed on the trailing edge of the wings on both sides, which can change the wing area and wing section through the movement of the carriage, and can be operated manually if the hydraulic equipment fails, and the tail rudder surface includes 3 rudder and 2 elevator rudders, the rudder is different from other parts, it is not an all-metal structure, but a fabric skin.
The aircraft is made of aluminum alloy, semi-monocoque structure, the entire length of the aircraft is about 29 meters, the maximum diameter is about 3.5 meters, the cockpit and passenger/cargo hold of the aircraft have pressurized equipment, and the air is provided by centrifugal mechanical compressors.
The C-69 is mainly used for personnel transport, with 60 seats in the cabin, 2 toilets to use, and military aviation equipment such as radio stations, navigation/landing aids, etc.
The aircraft originally designed as a global airliner also has some structural defects, such as its fuselage and part of the wing are built as a whole, which is not very convenient for mass production, and the production quantity of other large aircraft in World War II is indeed very small, and this structure is not conducive to maintenance and repair; 。
Lockheed had great hopes for the C-69, which was absolutely top-notch in terms of load and flight capability during World War II, and they also tried to develop a 100-seat C-69A transport version, a C-69B long-range cargo transport version, etc., which for various reasons did not materialize. In World War II, when aviation technology exploded, the proud performance of the C-69 was not the only one, and the U.S. military was more optimistic about the Douglas C-54.
The Lockheed C-69 "Constellation" transport aircraft has an empty weight of about 22,680 kg, a maximum take-off weight of about 32,600 kg, a length of about 29 meters, a height of about 6.8 meters, a wingspan of about 37 meters, a maximum flight speed of 530 km / h, a cruising speed of 365 km / h, a maximum ceiling of about 7,600 meters, and a maximum range of about 3,900 km.