 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
CRTs;
- 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.
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