The 2nd flying prototype of the Su-9K front-line fighter (so-called "double") was labelled "LK" (Su-11); its construction was started in September 1946. In terms of the design of its basic assemblies, equipment and armaments, the Su-11 did not differ much from the Su-9, with the exception of brake flaps (they were absent).
The wind tunnel studies of the models carried out using CAHI's facilities validated the assumption that the aircraft's flight performance could be improved subject to the engine nacelle profile being altered from the original configuration, with the engines suspended under the wing, in a symmetrical arrangement, "flush" with the wing. The double was initially specified for up-rated RD-10 engines, but in mid-December it was decided to substitute for them USSR-made TR-1 turbojets designed by A.M. Lyulka.
Official authorisation for developing a version with TR-1 engines was given in the USSR CM resolution of 11th March 1947, which enacted the 1947 aircraft prototype development plan. In April 1947 assembly was completed, and on 11th May the plane was brought to the MAI FRI airfield; a team of test personnel, with pilot G.M. Shiyanov and senior engineer V.P. Baluyev among them, initiated flight testing. On 28th May 1947 the Su-11 aeroplane was taken off the ground for its maiden flight. The manufacturer's tests, which were combined with TR-1 engine tests, were completed on 15th April 1948.
The manufacturer's flight test report said that:
". 1. The basic FP of the Su-11 with two TR-1s obtained in the course of the manufacturer's testing, are within the design parameters.
2. There being no TR-1A engines available and the CAHI recommendations to improve the aeroplane's behaviour at high Mach-number speeds having failed to produce a significant effect, we find it impractical to continue R&D work on the aircraft."
As a result, as early as 29th April 1948, the Su-11 was officially decommissioned.
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