Sukhoi T-4 Sotka – The Soviet XB-70

The Sukhoi T-4 Sotka was the Soviet’s attempt at a high-speed reconnaissance aircraft that would also have bombing capability.

You may notice something strangely familiar about the T-4… XB-70 anyone?

Also known as the Su-100, she was capable of an extremely high cruise speed of around 2,000 mph (3,200 km/h). Alas, this project failed – let us take a look at why.

Contents

Development & Design

In early 1963 the Soviet government wanted a new high-speed aircraft capable of flying at altitudes above enemy fighters and surface to air missiles.

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She was to be predominately used for photographing enemy territory. The American A-12 Oxcart was introduced and flew from 1963. Although top secret, the Soviets must have known such an aircraft existed and wanted some of their own that could match it.

The USSR’s design requirements were for a Mach 3+ capable aircraft that was very similar to the A-12 and XB-70. However, the Soviets were behind in terms of this technology and its first flight wouldn’t take place until 1972, almost 10 years after the A-12.

XB-70 in flight.
The XB-70 is one of the most incredible and advanced aircraft ever built. It shares many visual similarities with the Sukhoi T-4.
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Huge amounts of money were poured into the project as a lot of the machinery to build such a plane would require never used before tooling and over 600 new patents were created for this program alone!

Looking at the design, you’d assume they’d of used tracing paper and copied the XB-70, made a couple of tweaks and called it their own.

However, this is a perfect example of convergent design. If you want a fast, high altitude aircraft, it needs to look like this.

In nature, this is a fairly frequent occurrence where two completely separate species will have something almost exactly in common yet not be related in any way because it is the best way to achieve the goal. This was the case between the Soviet and American designs. 

Sukhoi T-4 at museum
While the Sukhoi T-4 and XB-70 certainly share visual similarities, they were built for different purposes. Image by Alan Wilson CC BY-SA 2.0.

To survive at Mach 3+, the T-4 was constructed mostly out of stainless steel and titanium, like the XB-70. Both the XB-70 and the T-4 were extremely advanced aircraft that pushed their respective builders to their technological limits.

Its pilots controlled the aircraft via a fly-by-wire (FBW) system. A backup mechanical system was also fitted in case of a failure with the FBW.

She was powered by four Kolesov RD-36-41 afterburning turbojet engines with each one producing 35,000 lbs of thrust with the afterburners. These were the same engines used on the Tu-144.

Sukhoi T-4 engines
The engines were mounted in a row below the aircraft. Image by Alan Wilson CC BY-SA 2.0.

If the aircraft ever went into service, those engines would have certainly been upgraded for increased performance as there were newer versions of the RD-36 available with a higher output of thrust.

The most distinct feature of the T-4 is its “droop snoot”. The nose of the aircraft could be lowered and raised to improve the pilots’ visibility on the ground, a system also used on the Concorde.

T-4 droop snoot.
The T-4’s droop snoot gave excellent visbility on the ground, but none in the air.

However unlike the Concorde, when the aircraft was in flight the pilots had terrible visibility. In fact, they had absolutely no view out of the front of the aircraft at all, and had to rely purely on instruments.

A periscope was fitted to alleviate these issues slightly, but it could only be used at speeds below 370 mph (600 km/h).

T-4M

A second version of the T-4 was proposed with a variable swing-wing – similar to the B-1 Lancer. This was going to be the strategic bomber variant.

The payload was to be a massive 45 tons and consist of anything from anti-ship weaponry to traditional ordnance and even nuclear bombs. Very little is known about this version other than it was proposed and a total of 36 variants were tested. 

Operational Use

By 1974 four airframes had been produced; three for flying, one for static tests. With the T-4 the Soviet’s aviation industry learned a lot about aircraft design in a relatively short space of time.

Creating a vehicle that can move a Mach 3+ without the help of computer design and testing is an incredible feat, even if it did take 10 years longer than the Americans.

The first flight of the T-4 was in August of 1972 and was successful. But by January 1974 only a total flight time of 10 hours and 20 minutes had been accrued. With such a short amount of time in the air, the full performance characteristics were never fully tested, only ever reaching Mach 1.3 and 40,000 ft.

Sukhoi bomber now resides in the  Central Air Force Museum in Monino near Moscow.
The technically impressive T-4 was cancelled after only 10 tests flights. Image by Samantha Cristoforetti CC BY 2.0.

By mid-1974 the project had been suspended and a year later, totally scrapped. Although it is often compared to the XB-70, the T-4 was a significantly smaller aircraft, designed to operate over much smaller distances.

The first flying prototype that was built still survives and lives in the Central Air Force Museum near Moscow as a feat of engineering to be remembered despite its lack of success.

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Specifications

  • Crew: 2
  • Length: 44 m (144 ft 4 in)
  • Wingspan: 22 m (72 ft 2 in)
  • Height: 11.2 m (36 ft 9 in)
  • Empty weight: 55,600 kg (122,577 lb)
  • Max takeoff weight: 135,000 kg (297,624 lb)
  • Powerplant: 4 × Kolesov RD-36-41 afterburning turbojet engines, 35,000 lbf of thrust each with afterburner
  • Maximum speed: 2,000 mph (3,200 km/h)
  • Ferry range: 7,000 km (4,300 mi, 3,800 nmi)
  • Service ceiling: 20,000–24,000 m (66,000–79,000 ft)