K-6 Postal Aircraft / Bomber

It was easy to see that with all the reorganizations of the late 1920s and early 30s, the Kharkov Aviation Plant invariably retained the word "experiental" in its name. This category included not only the first aircraft, which later went into mass production. A significant number of machines were created to work out some ideas, in an experimental form. Some, though planned for series production, for various reasons remained in single copies. But each of the constructed aircraft necessarily contributed something to the development of aviation,

One of the most experiental aircraft, which was worth recalling, was the K-6 airliner designed by Kalinin. The machine was developed in two versions: mail and bomber. The last, however, remained on paper, and the construction of the postal aircraft began in mid-1929 under the leadership of Deputy Chief Designer A. Ya. Shcherbakov.

According to the plan, the K-6 was the further development of the K-4 and K-5 models. The fuselage was welded, made of steel pipes. The elliptical wing was docked with the fuselage by means of two struts. To improve the aerodynamic qualities on the engine, a fairing was put on, and the propeller was installed. The crew of the aircraft consisted of two people - a pilot and a mechanic. They were located in the open cockpit, the pilot in the front part, and the mechanic in the back.

In addition to them, in the fuselage without special facilities could accommodate two more passengers. But this, as they say, just in case. After all, the main purpose of K-6 was mail. The machine raised from 240 to 400 kg of mail cargo, which was considered quite sufficient. The fuel reserve in four tanks allowed to stay in the air for up to ten hours. The plane had a radio station and equipment for night flights. The first radio station in the USSR on a civilian plane appeared in 1930 on the serial Kharkov K-4.

K-6 took off in the air on August 9, 1930. Piloted the plane by the tester Snegirev, the mechanic's place was occupied by Keglevich. The flight lasted 40 minutes and showed good flying qualities of the new car. State tests of K-6 were carried out at the Research Institute of Civil Aviation in March 1931. They did not identify the special advantages of the aircraft. The cruise speed was only 166 km / h, the maximum on the measured kilometer was 210 km / h, although the design proposal promised much more - 240 km / h. Still, the state tests were considered successful. In June 1931, K-6 was transferred to Aeroflot.

The plane received the registration number of the USSR-59 and began to regularly deliver the matrix of the newspaper "Pravda" from Moscow to Kharkov, covering the distance between the cities in 3 hours and 20 minutes.