The Sukhoi T-4 & Tupolev Tu-160

v1.0.4 / 01 mar 15 / greg goebel / public domain

* Although the Soviet Union more or less abandoned development of piloted supersonic bombers in the early 1960s in favor of long-range missiles, by the late 1960s work on such aircraft had been revived. The Sukhoi organization developed a flying prototype of the "T-4", which had some resemblance to a scaled-down version of the US XB-70 experimental bomber. The T-4 did not enter production, but a larger supersonic bomber, the Tupolev "Tu-160", did enter service, and remains in operation in the 21st century. This document provides a history and description of the T-4 and Tu-160.

Tupolev Tu-160 Blackjack

[1] SUKHOI T-4
[2] TU-160 ORIGINS

[1] SUKHOI T-4

* During the 1950s, Soviet Premier Nikita Khrushchev displayed a strong bias towards long-range missiles as the USSR's primary strategic nuclear delivery system, with a number of promising manned bomber concepts killed off as a result. In the late 1950s and early 1960s, however, American supersonic bomber efforts -- including the Convair B-58 Hustler and particularly the North American XB-70 -- persuaded the Kremlin that the Soviets should respond with a supersonic bomber of their own.

As specified, the new bomber was to have a top speed of Mach 3 and a cruise speed of Mach 2.8, with a typical Soviet capability of operating off unimproved airstrips. It was not actually planned as a rival to the American's intercontinental XB-70, the Soviet machine being intended as a medium-range aircraft to attack tactical ground targets and Western naval task forces. It was to carry air-to-surface missiles (ASMs) to provide a standoff strike capability. The aircraft was also to be used for the strategic reconnaissance mission.

The Tupolev, Yakovlev, and Sukhoi experimental design bureaus (OKB in the Russian acronym) all submitted proposals. The Yakovlev concept didn't meet requirements and was quickly discarded, with a protracted bureaucratic tug-of-war between the Tupolev and Sukhoi OKBs following. Somewhat surprisingly, since Tupolev had become established as the USSR's main builder of bombers, Sukhoi won the competition, with the OKB's engineers moving on to an advanced design study of the "Izdeliye 100 (Product 100 / I-100)", or "T-4" as it was known. Along with bomber and reconnaissance variants, the Sukhoi OKB also considered heavy fighter and supersonic transport (SST) derivatives of the basic aircraft design. The refined bomber design was submitted to the state apparatus in April 1963, leading to approval for full development of the T-4, with initial flight then scheduled for 1968.

The configuration of the aircraft evolved considerably through its design history, but the finalized design was a dartlike machine, with a slender fuselage, cranked "double delta" wing, canard foreplanes, and four afterburning turbojet engines in a unitary "wedge" nacelle under the centerline between the wings. A full-scale mockup was completed in late 1966, featuring provisions for both the standoff-missile carrier and reconnaissance configurations -- the airframe being much the same, just with different equipment fits. Work then went forward on the construction of two prototypes, including a flight prototype and a ground-test airframe.

* Development of the T-4 pushed the state of the art of Soviet aircraft design and the flight prototype, numbered "101", was not actually rolled out until late 1971. The aircraft was very rakish, with its double-delta wing featuring a leading-edge sweep of 74 degrees 44 minutes inboard and 60 degrees 7 minutes outboard. There were three-section "elevon" control surfaces at the back of each wing, and a two-section rudder; the canards appear to have been all-moving, though sources are not clear on that detail. Various wing configurations for the T-4 had been flight-tested on a Sukhoi Su-9 interceptor in 1966 to validate the wing configuration. Similarly, the T-4's canard nose fins had been flight-tested on an Su-7U trainer in 1968. Still more flying testbeds trialed avionics and other systems.

North American XB-70 Valkyrie VS Sukhoi T-4

The T-4 was powered by four Kolesov RD36-41 turbojets, providing a maximum thrust of 156.9 kN (16,000 kgp / 35,273 lbf) each in afterburner. There were only two inlets for the four engines. Landing gear consisted of two-wheel nose gear, retracting backwards into the front of the engine nacelle; and eight-wheel main gear, in a 2x4 configuration, on the rearward corners of the nacelle that apparently retracted up and forward. A brake chute assembly, with four cruciform parachutes, was stowed in the extreme tail and was deployed to reduce landing roll.

The T-4 was a "dynamically unstable" aircraft, and so an advanced analogue-electronic "fly by wire (FBW)" flight control system was developed to keep it flying right; an automated throttle system or "auto-throttle" was also developed since engine management on landing could be tricky. In full flight the T-4 was effectively flown on instruments, with the only effective cockpit glazing being two small windows on each side. For takeoffs and landings, the nose drooped down to reveal a three-panel windshield. There were two crew, including pilot and navigator / weapons system operator. They sat in tandem and got in or out of the machine through individual hatches on top of the cockpit, positioned off-center to the left, with the hatches hinging upward from the rear. Apparently the crew sat on upward-firing ejection seats, but sources are also not clear on this matter.

   SUKHOI T-4:
   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                22 meters           72 feet 2 inches
   wing area               295.7 sq_meters     3,180 sq_feet   
   length                  44.5 meters         146 feet
   height                  11.19 meters        36 feet 8 inches

   empty weight            54,800 kilograms    120,810 pounds
   normal loaded weight    128,000 kilograms   282,185 pounds
   MTO weight              136,000 kilograms   299,825 pounds

   max speed at altitude   3,200 KPH           1,985 MPH / 1,730 KT
   service ceiling         20,000 meters       24,000 feet
   range (no tanks)        6,000 kilometers    3,725 MI / 3,245 NMI
   _____________________   _________________   _______________________

Baseline offensive armament was to be two Raduga Kh-45 long-range standoff missiles, being developed concurrently, for antiship or land attack, armed with conventional or nuclear warheads. The T-4 was to be fitted with appropriate navigation / fire-control radar and datalinks for targeting systems, but details are again unclear. There was no defensive armament, the T-4 relying on speed and a sophisticated electronic countermeasures (ECM) suite for protection. External fuel tanks could be carried to extend range. Reconnaissance gear was to include film cameras, infrared imagers, and a side-looking airborne radar (SLAR), with the reconnaissance gear at least partly carried externally. Maximum payload was 19 tonnes (20.9 tons).

Work on the T-4 required advances in production of parts made of titanium and heat-resistant steel, with an automated production facility set up to streamline the task. Such a complicated aircraft was seen as a handful for two crew, so automated systems were also developed to reduce crew workload. A new "high-flashpoint" fuel was developed to permit safe fuel storage at high airframe temperatures. The T-4 was nicknamed the "Sotka", meaning "Hundred" and standing for the I-100 product code. Thanks to the product code, the aircraft was occasionally referred to in the West as the "Su-100", but the Soviets never referred to it in such a way.

* The Sotka performed its initial flight on 22 August 1972 from the Zhukovskiy test center near Moscow, with well-known test pilot Vladimir Ilyushin at the controls and Nikolay Alfyorov in the navigator's seat. The flight had been delayed because of forest fires in the area that filled the sky with smoke. The T-4 performed nine more test flights, reaching Mach 1.28 on the second to last. There were various bugs that needed fixing, but otherwise the aircraft clearly seemed to meet performance spec; handling was very good, all the way from taxiing to high-speed flight. Field of view for landings with the nose drooped was judged excellent.

A second prototype, tailcode "102", had been completed and more prototypes were in construction, with an order for 250 production machines in the wings, when the project was canceled. The Tupolev OKB had been able to sell the Kremlin on their own solution for the theater bomber requirement, the "Tu-22M". The name was misleading, identifying it as a follow-on to the unsatisfactory Tu-22 Blinder when it was effectively a completely new design that nobody could mistake for the Blinder. It went into production, to be given the NATO codename of "Backfire", and the T-4 was history.

Sukhoi T-4

The 101 flight prototype of the T-4 only took to the air ten times, with the last flight on 22 January 1974. It finally ended up in the air museum at Monino, where it survives to this day. The 102 flight prototype never left the ground and was eventually scrapped. The Sukhoi OKB came up with paper designs for refined follow-ons, with features such as variable geometry ("swing") wings and stealth, but as discussed below, they didn't happen.


[2] TU-160 ORIGINS

* Although the North American XB-70 bomber project had been canceled in the early 1960s, the USA continued to tinker with various advanced manned bomber concepts through the decade, which would lead to the development of the Rockwell B-1 from the 1970s. The Soviets were perfectly aware of the American bomber studies, and in November 1967 the authorities issued a requirement for a new long-range strategic bomber of their own, envisioned as a high-altitude, long-range, Mach 3 machine primarily armed with standoff weapons.

As mentioned above, the Sukhoi OKB proposed a derivative of the T-4, the "T-4M", featuring swing wings. Analysis of this design eventually showed that it left something to be desired, and so Sukhoi engineers came up with a new proposal, designated the "T-4MS", though it had little or nothing in common with the original T-4. The T-4MS was an odd-looking machine, something like a triangle with two corners chopped off and a swing wing inserted in the cut on each side.

The design OKB under the direction of Vladimir Myasishchev -- which had built the subsonic M-4 "Bison" and the one-off supersonic M-50 "Bounder" heavy jet bombers before being disbanded in 1960, to be resurrected in 1966 -- worked on their own concepts in parallel, under the designation "M-20". The initial concept was a swing-wing aircraft with a strong resemblance to a scaled-up version of the US General Dynamics F-111 "Aardvark". This led to a canard aircraft with a "cranked arrow" wing; then concepts for canards with swing wings; and finally a concept for a swing-wing aircraft with a conventional rear tail assembly that had a resemblance to the US B-1.

Myasishchev M-20 concepts

In 1970, the Tupolev OKB entered the competition, proposing a series of double-delta flying wing machines under the designation of "160M". The final selection turned out to be complicated; there was an initial round of consideration in 1972 that came out in favor of the Sukhoi T-4MS, but the conclusion was that the initial requirements simply could not be met by any of the designs. The top speed requirement was dropped to Mach 2+ -- though there was no flexibility on the range requirement -- with the various OKBs then submitting revised proposals. The authorities selected from them the Myasishchev "M-18", which was a simplified and slightly modified version of the final M-20 design, with swing wings and a conventional tail assembly. Ironically, since the Myasishchev OKB lacked the resources to develop such a complicated aircraft, full development was passed on to the Tupolev OKB.

* Turning what amounted to a general concept of an aircraft into something that flew was of course not trivial, and a full-scale mockup of the Tupolev "Tu-160", as it had been designated, wasn't available until 1977. The mock-up was approved and work then began on three prototypes, including two flight prototypes and one static-test airframe.

The initial flight prototype, tailcode "70-01", was assembled at the Zhukovskiy flight test center near Moscow and performed its initial taxi test on 14 November 1981. Initial flight was on 18 December 1981, with Boris Veremey at the controls, accompanied by copilot Sergey Agapov, plus navigators Mikhail Kozel and Anatoliy Yeremenko. Three months later, Veremey took 70-01 to its top speed of 2,200 KPH (1,365 MPH). It was photographed by a foreign airline passenger coming into Moscow, with the prototype sitting next to two Tupolev Tu-144 SSTs. The passenger published the photo. Since the name of the Zhukovskiy test center was not known outside the USSR at the time, it was known as "Ramenskoye" after a nearby town, and the mystery aircraft was accordingly codenamed "Ram-P". It was later given the NATO codename of "Blackjack".

The initial flight prototype was not close to operational specification; the second flight prototype, "70-03", was essentially a preproduction machine, very near service spec, and unsurprisingly it took a lot more work to bring the design to that state. As a result, the second flight prototype didn't take to the air until 6 October 1984. Production had already been authorized, to take place at a state factory in Kazan, with the first production machine flying on 10 October 1984 -- less than a week after the initial flight of 70-03. However, bringing the Tu-160 into operational service was, once again, not trivial, and the VVS (Voyenno Vozdushniye Sily / Red Air Force) didn't declare the type operational until April 1987. The first squadron was complete by the end of 1988; two squadrons had been filled out by the time the Soviet Union collapsed in 1991. Incidentally, at last notice the initial flight prototype remains at Zhukovskiy in a state of disrepair.



* The Tupolev Tu-160 has a general resemblance to the US B-1, though the Tu-160 is a substantially bigger aircraft and has little similarity in detail; nobody at all familiar with aircraft would confuse the two. As mentioned, the Tu-160 has a low-mounted swing wing, with "wing-body blending" between the fuselage and the inner fixed wing glove sections, and a conventional swept tail assembly. Construction is unclear -- it appears to be made mostly of aircraft aluminum alloy, with some titanium and some composite assemblies.

Tupolev Tu-160 versus Rockwell B-1

The Tu-160 is powered by four Kuznetsov NK-32 afterburning bypass turbojets with a maximum dry thrust of 137.3 kN (14,000 kgp / 30,872 lbf) and a maximum afterburning thrust of 245.2 kN (25,000 kgp / 55,140 lbf) each. There is an engine pod under each wing glove, with twin engines in each pod; the inlets are variable, using hinged ramps mounted on the centerwall of each split inlet. The engine pods feature large hinged panels to ease service crew access and swapout of engines.

There are 13 fuel tanks in the center wing-body section and swing wings, and there is a pop-up inflight refueling probe in the nose ahead of the cockpit. The Blackjack has tricycle hydraulically-actuated landing gear, with twin-wheel nose gear that retracts backwards, and six-wheel main gear arranged as three rows of duals that retracts back into the fuselage just inboard of the engine pods. A brake chute system, with three cruciform parachutes, reduces landing roll.

There are three wing sweep settings, from 20 degrees when the wings are fully extended for takeoff or landing; to 35 degrees for high-speed cruise; and to a fully-swept 65 degrees for Mach 2 dash. The control surface arrangement on the pivoting wing sections is elaborate, with each wing featuring three-section double slotted flaps; a five-section spoiler ahead of the flaps; an aileron outboard; and a four-section leading-edge flap. There is an unusual moveable surface at the rear of the wing near the wing joint, which folds flat when the wings are extended to cover the "gap" between the rear wing glove and swing wing, while being pivoted vertically to act as a "wing fence" of sorts when the wings are fully swept.

The tailplanes are mounted on the tailfin a short distance above the fuselage and are all-moving. They can be pivoted in alternate directions for roll control, the ailerons only being used when the wings are fully extended. There is no rudder, the tailfin being all-moving above the tailplane. Incidentally, the Myasishchev M-20 concept that led to the Tu-160 had a tee tail, though the configuration was otherwise similar to the aircraft that actually flew.

   TUPOLEV TU-160:
   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan (extended)     55.7 meters         182 feet 9 inches
   wing area (extended)    293.2 sq_meters     3,155 sq_feet   
   wingspan (swept)        35.6 meters         116 feet 10 inches
   wing area (swept)       232 meters          2,497 feet 10 inches
   length                  54.1 meters         177 feet 6 inches
   height                  13.1 meters         42 feet 11 inches

   empty weight            117,000 kilograms   257,940 pounds
   MTO weight              275,000 kilograms   606,260 pounds

   max speed at altitude   2,200 KPH           1,365 MPH / 1,190 KT
   service ceiling         15,600 meters       51,180 feet
   range                   12,300 kilometers   7,640 MI / 6,640 NMI
   _____________________   _________________   _______________________

There are twin tandem weapons bays, each 11.28 meters (37 feet) long and 1.92 meters (6 feet 4 inches) wide. Standard armament consists of 12 Raduga Kh-55 or enhanced-range Kh-55SM (NATO AS-15B Kent) cruise missiles -- similar to the US Tomahawk cruise missile -- with six on a rotary launcher in each weapons bay. The Tu-160 can also carry the "Kh-555", a conventionally-armed conversion of the Kh-55 An alternate warload, apparently not carried much in practice, consists of 24 Raduga Kh-15 (NATO AS-16 Kickback) solid-fuel standoff missiles -- similar to the US SRAM missile -- with six each on four rotary launchers, two launchers per weapons bay.

The Raduga Kh-45 standoff missile envisioned for the T-4 was initially regarded as the primary store of the Tu-160, but the Kh-45 was canceled. A new "Kh-102" cruise missile, something like a bigger, stealthier derivative of the Kh-55, is being fielded, with six carried on a bomb bay rotary launcher. In principle, the Tu-160 can also carry up to 40 tonnes (44 tons) of nuclear or conventional free-fall munitions, though at the outset it was not assigned any conventional strike role.

Avionics include:

Of course, the Tu-160 has standard avionics such as radios and identification friend or foe (IFF) transponder. While Russian sources are unsurprisingly tight-lipped about defensive systems, the Blackjack carries passive warning systems, active jamming systems, and chaff-flare dispensers. The aircraft uses a distributed digital control system built around a network of a hundred processors, and a quadruple-redundant FBW flight control system. There is a backup mechanical flight control system, but given that the Tu-160 is dynamically unstable, it is unclear just how useful it might be in practice.

There are four crew sitting in the pressurized cockpit in a 2x2 arrangement, including pilot (front left seat), co-pilot (front right seat), navigator / offensive systems operator (back left seat), and navigator / defensive countermeasures systems operator (back right seat). All crew sit on Zvezda K-36LM "zero zero (zero altitude zero speed)" ejection seats, which fire upward through doors on the roof of the cockpit. The ejection seats were eventually modified to pneumatically "pulse" to provide a massage, reducing crew weariness on long missions. The pilot and copilot have fighter-like sticks instead of yoke controls; cockpit layout is traditional, based mostly on dial indicators and displays, archaic by Western standards. A small galley and toilet are provided for crew comfort, unusual luxuries by the standards of Soviet-Russian combat aircraft. The crew get into and out of the aircraft through a door in the nose gear wheel well.

The normal color scheme for the Tu-160 is overall white, which has led aircrews to nickname it the "White Swan". Individual aircraft are generally named after Russian heroes.



* By the time of the collapse of the Soviet Union in 1991, 35 Tu-160s had been built or were on their way to completion. With the breakup of the old Soviet empire, 19 of these aircraft ended up in the hands of Ukraine; the Russians inked a deal with the Ukrainians in 1999 to obtain eight of these Tu-160s, in exchange for debt forgiveness. The Ukrainians, who had declared themselves a non-nuclear power, scrapped the rest, except for one reserved as a museum display.

Tu-160 Blackjacks in flypast

As of 2015, there were 16 Tu-160s in service with the VVS, it seems including a number being used in trials; the goal is to bring the fleet up to 30, via rebuilds or new production. The small number of Tu-160s in VVS service have a visibility all out of proportion to their numbers, since in 2007 Russian President Vladimir Putin announced that Russian would resume strategic flights that had been abandoned from 1991. Since that announcement, the Tu-160s have flown across the oceans and occasionally brushed Western airspaces, to be escorted by intercepting fighters. The strategic flights are strictly political in nature, little more than a symbol that Russia still remains a strategic military power.

Only one model of the Tu-160 has been produced, but a number of others were considered, though ultimately not implemented:

One of the most interesting concepts was the "Tu-160SK", which was to be a carrier for the "Burlak" light space launch vehicle, hauled under the aircraft's centerline. The Burlak was to be able to put about a tonne in low Earth orbit. A Tu-160 dummied up as a Tu-160SK was displayed at the Paris Air Show in 1995, that being the first time a Tu-160 was flown to the West for a close inspection. The Burlak program ended up on hold.

During the 1980s, the Tupolev OKB conducted studies on a Mach 4 "Tu-260" and a Mach 6 "Tu-360" follow-ons. They had little resemblance to the Tu-160, looking more like some kind of space shuttle; neither project went anywhere, which was just as well. As the speed of an intercontinental-range aircraft increasingly goes above Mach 3, it becomes more and more sensible to consider a suborbital vehicle that doesn't have to worry about the atmosphere getting in the way. There was more realistic work on a flying-wing bomber, the "B-90", somewhat comparable to the US B-2 Stealth Bomber, but the B-90 also came to nothing.

* Although none of the follow-on Tu-160 variants actually happened, they did contribute ideas and technology for improvements to the existing Tu-160 fleet. Blackjacks now in service with the VVS are to be updated to "Tu-160M" standard, with the update including:

Tupolev Tu-160

Initial flight of an upgraded aircraft was in late 2014. In 2013, the Russian government announced the intent to obtain a replacement, possibly in the form of a Tupolev flying-wing design along the lines of the US B-2 Stealth bomber. The project is designated the "Prospective Aviation Complex for Long-Range Aviation" or "PAK-DA" in its Russian acronym, with initial flight scheduled for 2019 and introduction to service in 2023. However, given the likely lead times on that project, the Tu-160 is certain to remain in service for the foreseeable future.



* Sources include:

Some comments were also obtained from the Wikipedia article on the Tu-160.

Sukhoi T-4M

* Revision history:

   v1.0.0 / 01 dec 09 
   v1.0.1 / 01 nov 11 / Review & polish.
   v1.0.3 / 01 oct 13 / PAK-DA.
   v1.0.4 / 01 mar 15 / Review & polish.