Sukhoi Su-35
By Sergei Drobyshev
Picture by: Neville Dawson
Subj: SU-35: AIRCRAFT OF THE 21st CENTURY
by Sergei Drobyshev
Head of the Regional Policy and Marketing Department, KnAAPO
Via Easy Tartar
The development of a new combat aircraft is a most intricate gestation period from the R & D work to launch it into series production and operation. A major role here is played by the manufacturer, because there is a long way between the creation of a prototype and the production of a series aircraft. So, during the launch into series production of the Su-27 aircraft developed with the direct participation of specialists from the Komsomolsk-on-Amur Aircraft Manufacturing Company (KnAAPO), over 50,000 revisions and corrections have been introduced into the designs of the airframe and airborne systems. Without the concerted efforts of KnAAPO, Sukhoi EDB and hundreds of allied enterprises, this wonderful machine would remain a mere blueprint. The design potential of the Su-27 aircraft made it possible for the Sukhoi EDB to develop, on its basis, some new versions of combat aircraft for various roles, such as the Su-27UB combat trainer, Su-30 multipurpose two-seater, Su-33 deck-based fighter, Su-32FN front-line bomber and, of course, the Su-35 multipurpose fighter. A pioneer in the production of the Su-27s, KnAAPO also contributed to the creation of these aircraft, generously sharing its technical and technological know-how tried out on the Su-27s, with other aircraft manufacturing factories which brought the production of these aircraft to the commercial level.
As soon as the work on the Su-35 was started by Sukhoi, the KnAAPO specialists actively participated in the project, designing units and assemblies for the future aircraft. Most experimental aircraft for the trials and a small series of them for the Russian Air Force have also been built by KnAAPO.
To enhance the combat effectiveness and expand the employment area of the aircraft, it was decided to create a multipurpose maneuverable fighter combining high agility and capacity to intercept air targets normally attacked by the Su-27 with a capability to attack ground and water surface targets by both unguided and guided, including high precision, weapons. The Su-35 met these requirements.
The Su-35 is intended to destroy existing and prospective remotely piloted vehicles, cruise missiles and other maneuverable targets against the earth background, day and night and in all weathers, to deliver preemptive strikes at any air enemy, including hardly discernible visual objects, to engage ground (and water surface) targets by carrying out standoff attacks with diverse guided weapons, including high-precision ones.
The installation of a new set of airborne equipment and additional (as compared to the Su-27) weapon systems on the aircraft required more hardpoints, a robust airframe, and called for changes in many airborne and airframe systems. The main landing gear struts have been modified and the two-wheel nose leg ruggedized.
For better agility and takeoff/landing performance, the aircraft was provided with a canard. In terms of aerodynamic layout, the Su-35 is an unstable integral triplane (wing + horizontal tail + canard). The required stability and control are assured by a remote control system. The canard notably assists in controlling the aircraft at large angles of attack and bringing it to a level flight condition. The Su-35 has now acquired a newly developed wing with increased relative thickness, accommodating a large amount of fuel. As in the Su-27, the wing of the Su-35 is provided with high-lift devices featured as deflecting leading edges and flaperons acting as both the flaps and ailerons. In flights at subsonic speeds, the wing profile curvature is changed by a remote control system which deflects the leading edges and flaperons versus the angle of attack.
The horizontal tail of the aircraft is essentially a differentially adjustable stabilizer each panel of which is provided with its own quick-acting electro-hydraulic actuator. For a greater combat employment range, the aircraft is fitted with an in-flight refueling system. Inasmuch as a refueling flight of the aircraft may be quite extended (6 - 8 hours or longer) and is only limited by the pilot's physical conditions, its cockpit is provided with containers to store reserves of food and water, and a waste disposal system. The amount of oxygen is increased too. The KD-36DM series ejector seat is set with its back inclined at 30 deg., which helps the pilot resist aircraft accelerations in air combat.
The Su-35 avionics equipment comprises:
new-generation forward-looking pulse-doppler radar with a phased antenna array
rearward-looking radar
optical locator with combined functions of infra-red imager and laser range finder
weapons control system
helmet-mounted target designator
radio reconnaissance system
defense complex
integrated display system using three high-contrast monochrome CRT's
communications and navigation equipment
To penetrate enemy air defenses, the Su-35 can fly at low altitudes using its terrain following and obstacle avoidance feature.
The armament of the aircraft consists of a fixed gun, aerial bombs, guided and unguided missiles. The missile-bomb armament is arranged at 12 hardpoints and comprises:
prospective medium-range, type RVV-AE, air-to-air 'fire-and- forget' active homing missiles;
medium-range air-to-air missiles of the R-27 family with semi- active radar and passive IR guidance, with engines both conventional and having increased power-to-weight ratio
highly agile missiles of the R-73 class for close air maneuver combat with passive IR guidance and combined (air- and gas-dynamic) control
the X-31A and X-31P air-to-ship and air-to-radar missiles with active and passive radar guidance and capable of flying at a supersonic speed
the X-29 air-to-surface missiles with laser and TV guidance
incendiary tanks, 100-kg, 250-kg and 500-kg bombs and bomb clusters for various purposes, including those fitted with a brake and used for low-altitude attacks
Overall, over 70 versions of guided and unguided weapon stores may be employed, which allows the aircraft to fly most diverse tactical missions.
The flight-navigation equipment of the aircraft permits it to make flights in all weathers, day and night. The equipment includes a navigation complex, automatic flight control and remote control systems.
The navigation complex comprises an inertial directional system and short- and long-range radio navigation systems. The information produced by the systems goes to unified digital computers which compute the flight paths for a programmed route flight, target approach and return to the landing airfield.
The automatic flight control system of the Su-35 makes all phases of its flight automatic, including the combat employment of its weapons.
Once the automatic flight control system receives information from the navigation system, it solves the route flight tasks, involving a flight over the programmed waypoints, the return to the landing airfield, making a pre-landing maneuver and approach for landing down to an altitude of 60 m, as well as uses the data supplied from the weapons control and radio guidance command systems to direct the aircraft to the target and accomplish the attack.
For flight control, reliability and survivability, the aircraft has a remote control system with quadruple redundancy. Depending on the flight conditions, signals from the control stick position transmitter or automatic flight control system will be coupled to remote control amplifiers. Upon updating, depending on the flight speed and altitude, these signals are combined with feedback signals fed by acceleration sensors and rate gyros. The resultant control signals are coupled to the high-speed electro-hydraulic actuators of the stabilizers, rudders and canard. For greater reliability, all the computers work in parallel. The output signals are compared and, if the difference is significant, the faulty channel is disconnected.
An important part of the remote control system is based on a stall warning and barrier mechanism with an individual drive of its own. It prevents development of aircraft stalls through a dramatic (by 15 kgf) increase in the control stick pressure. This allows the pilot to effectively control the aircraft in a maneuver combat without running the risk of reaching the limit values of angles of attack and acceleration.
The stall control is accomplished by the computer of a signal limiting system, depending on the configuration and loading of the aircraft. The same system sends voice and visual signals, as the aircraft nears a stall condition.
The communications equipment of the aircraft comprises VHF and HF radio sets, a secured digital telecommunications system, and antenna-feeder assembly.
The aircraft mounts an automatic noise-proof target data exchange system, which provides for coordination of the actions of several fighters engaged in a group air combat.
An integrated ECM system turns on warning units that provide signals about attacking enemy missiles, a new generation radio reconnaissance set, active jamming facilities and radar and heat decoys.
The cockpit of the Su-35 boasts an up-to-date display system, which comprises three CRT indicators, head-up display, display system computers, and the computers of an integrated information system. All the required information is provided to the pilot on electronic indicators. The contents of the information frames can be changed to suit the pilot needs with the aid of the keyboard, while the data can also be altered automatically in the information frames depending on the flight conditions.
The integrated information system allows the performance of a ground serviceability test of the entire equipment and location of troubles to an individual plug-in unit. In case of in-flight failure, the indicator of the integrated information system will provide the pilot with a text message about the failure and recommendations on how to correct it or will dictate further actions. The message is also duplicated by voice.
Installation of the new avionics equipment with considerable power consumption necessitated increased capacity of the airborne electric and hydraulic power supplies. To this end, new and more powerful generators and hydraulic pumps have been installed.
A further development of the Su-35 is the Su-37, the newest superagile fighter powered by engines with a thrust vector control system. The system is integrated with the remote control system of the aircraft. The engine nozzles deflect in pitch by 15 degree up and down with the aid of two couples of hydraulic jacks mounted on each engine. The angular rate of the nozzles is up to 30 degrees per second. The system permits deflection of the nozzles in the same and different directions.
The employment of thrust vector control allowed the aircraft to master some new maneuvers, such as 'tumble in the air' (rotation through 360 degrees).
There are also some novelties in the aircraft avionics. For example, the cockpit indication system uses four liquid-crystal color displays provided by France's Sextant. These are widescope color displays assuring good readability of the information even in bright sun light. The aircraft is fitted with a satellite navigation system and laser attitude and heading reference system.
The employment of the new avionics largely contributed to the accuracy and reliability of the navigation system. The cockpit is also provided with a side control stick and engine control levers with a strain sensitive system responding to the pilot hand pressure.
The weapon control system and armament used aboard the Su-37 are mainly consistent with the ones normally employed by the Su-35 and can be enhanced.
An AL-35 engine now under development is intended for installation aboard the Su-35 and Su-37 aircraft. Installation of this engine will markedly improve the acceleration characteristics and maneuverability of the aircraft. Both aircraft have rather spacious compartments to accommodate the existing and prospective sets of avionics. So the design potential of the Su-35 and Su-37 is still far from being exhausted.
The Su-35 and Su-37 have all the merits allowing them to become the principal multipurpose fighters of the Russian Air Force in the beginning of the 21st century. Under respective cooperation agreements signed by the Russian Federation with foreign countries in military and technological spheres, these aircraft may also be supplied to foreign customers.
Characteristics of Su-35:
Crew 1
Maximum takeoff weight, kg 34,000
Weight of empty aircraft, kg 18,400
Maximum warload, kg 8,000
Power plant, number x type of engine 2 x AL31FM Maximum afterburning thrust, kg 12,800
Maximum flight speed, km/h:
near ground 1,400
at high altitude 2,500
Service ceiling, m 18,000
Flight range, km:
with internal fuel reserve 3,200
with one refueling 6,500
