Sukhoi T-4 - bomber with 600 Soviet patents

Sukhoi designed the T-4 with the most advanced Soviet technology, many of which are still used on the current Su-35 fighter.

The only surviving Sukhoi T-4 prototype. Photo: Flickr

In 1963, the Soviet government issued a request for a strategic bomber to compete with the XB-70 Valkyrie being developed by the US. Three design bureaus, Sukhoi, Yakovlev and Tupolev, proposed their projects, with Sukhoi's T-4 version being selected for trial production, according to Airwar.

Chief designer Pavel Sukhoi was the head of the T-4 design team. Previously, the Sukhoi design bureau (OKB) specialized in developing jet fighters and had no experience in building bombers.

Sukhoi's teacher, chief designer Andrei Tupolev, tried to dissuade him from participating in this project. However, Pavel Sukhoi was determined to build the T-4 with his colleagues and beat his teacher in the Soviet government's tender.

The Sukhoi T-4 is capable of cruising at speeds of up to 3,200 km/h, three times the speed of sound (Mach 3). This helped Pavel Sukhoi's design beat rivals Yakovlev and Tupolev. After the review phase in June 1964, the construction of the first Sukhoi T-4 prototype began.

The aircraft was nicknamed "Sotka" (100 in Russian) because the designers estimated its weight at 100 tons. The completed T-4 prototype weighed 120–135 tons, including fuel and weapons.

The development of the T-4 required a lot of research to create the technology that met the requirements. Notable among them were the method of manufacturing materials and titanium welding techniques to ensure the aircraft could withstand Mach 3 speeds. According to Sukhoi, nearly 600 inventions were published and applied during the development of the T-4.

The Sukhoi T-4 was made from titanium and stainless steel. It was the first Soviet aircraft to be equipped with a fly-by-wire electronic control system with 4 redundant channels, along with a traditional mechanical control system to ensure safety. The T-4's fly-by-wire technology was later applied to the Su-27 fighter line and upgraded versions such as the Su-30 and Su-35.

The nose of the aircraft is adjustable according to the speed of the aircraft. The nose is lowered during take-off and landing to increase the pilot's visibility. When cruising at high speed, the nose of the T-4 is raised to reduce air resistance. The pilot can observe outside through a periscope at speeds below 600 km/h.

Sukhoi T-4 in nose lift state. Photo: Sukhoi

The Sukhoi T-4 is 44 m long, 11.2 m high, and has a wingspan of 22 m. The aircraft is equipped with four Kolesov RD-36-41 jet engines with a total thrust of about 64,000 kgf, allowing the T-4 to cruise at a speed of 3,000 km/h with a weapon payload of 9 tons, reaching a maximum speed of 3,200 km/h and a range of 7,000 km. The main weapons of the T-4 include the Kh-45 supersonic anti-ship missile and conventional bombs with a maximum weight of 3 tons.

The first prototype was completed in mid-1971. Sukhoi continued to build three more T-4s, one of which was used for stationary ground tests.

The first T-4 prototype, serial number 101, took off on August 22, 1972, piloted by Vladimir Ilyushin and navigator Nikolai Alfyorov. Test flights lasted until January 19, 1974. Only 10 flights were made, with a total flight time of 10 hours and 20 minutes. In mid-1974, the Soviet Ministry of Aviation Industry ordered the suspension of the Sukhoi T-4 development. The project was officially canceled on December 19, 1975.

One of the reasons for the cancellation of the T-4 project was that the US had abandoned the XB-70 Valkyrie, the aircraft’s main competitor. In addition, the Soviet Air Force’s demand for 250 T-4s was considered unrealistic. The funds for building this bomber could have been used to produce a larger number of more practical aircraft.

Today, only 101 remains, on display at the Central Air Force Museum in Monimo, outside Moscow. This is also the model that carried out all the test flights of the T-4 project.

According to VNE