Sukhoi T-4
The Sukhoi T-4, or "Aircraft 100", or "Project 100", or "Sotka" was a Soviet high-speed reconnaissance, anti-ship and strategic bomber aircraft that did not proceed beyond the prototype stage. It is sometimes called the Su-100. Design and development. In 1963, the Soviet government held a request for proposal among the aircraft design bureaus, with the aim of developing an aircraft analogous to the North American XB-70 Valkyrie. The Sukhoi design, with its high cruise speed of was favored over the designs submitted by Yakovlev and Tupolev and after a preliminary design review in June 1964, the  building of a prototype was authorized. Development of the T-4 required massive research efforts to develop the technologies necessary, including the manufacturing technologies to machine and weld the materials necessary to withstand sustained Mach 3 flight. Nearly 600 patents or inventions are attributed to the program. The first flying prototype was finally completed in the autumn of 1971. Work continued on an additional three airframes (one for static testing) through 1975. In 1974, the Ministry of Aviation Industry ordered work suspended on the T-4 project, which was officially scrapped on 19 December 1975. The aircraft's droop nose lowered to  provide visibility during takeoff and landing. A periscope was used for forward viewing when the nose was retracted, and could be employed at speeds of up to . Drogue parachutes were used in addition to conventional wheel brakes. Operational history. The first T-4, designated "101", first flew on 22August 1972. The test pilot was Vladimir Ilyushin, son of famed aircraft designer Sergei Ilyushin, and navigator Nikolai Alfyorov. Testing continued to 19January 1974. The T-4 flew only ten times for a total 10 hours and 20 minutes. It is believed to have reached at least Mach1.3 at an altitude of using four  Kolesov RD36-41 engines. These engines each produced thrust with afterburners. The aircraft was designed to achieve speeds of up to Mach3.0 with nine tons of weapons (two MKB Raduga Kh-45 missiles) under the wings, but the program was cancelled before the full performance of the aircraft could be reached. . Aircraft on display. One T-4 survives. Aircraft "101" is on display at the Central Air Force Museum in Monino near Moscow. The serial numbers of the prototypes were "101" to "106". Only "101" and "102" were built, while other additional prototypes "103" and "104" were under construction, and "105" and  106 only existed on draft charts. Only the "101" completed all the test flights and flew the last test flight before the project was canceled on 22 January 1974. The rest of the prototypes were scrapped.