Su-35 bridges gap between current and next-gen fighters

 - June 15, 2009, 4:16 AM

Sukhoi believes it is within two years of making first deliveries of its new Su-35 fighter as it prepares to add a third prototype to the flight-test program before the end of this month. The famous Russian design bureau is pinning its hopes on what it bills as a bridge between fourth-generation combat aircraft technology and the long-anticipated fifth-generation fighter that it expects will enter service in the second half of the next decade.

The flight test program started in February 2008 and passed the 100-flight mark on March 19 this year. The three test aircraft are due to make up to 160 flights among them. This year, Sukhoi expects to conclude static and super-agility tests en route to first deliveries in 2011.

Working largely at the KnAAPO factory in Komsomolsk-on-Amur, Sukhoi has already completed static tests to prove the Su-35’s flight capabilities in critical modes and the stability performance of the aircraft. It has also tested the fighter’s integrated control systems, navigation equipment and other aircraft systems.

According to Sukhoi, the Su-35 is a “4++ generation” fighter that represents the early integration of some aspects of fifth-generation technology. The aircraft, which made its public debut almost two years ago at Moscow’s August 2007 MAKS airshow, is billed as an interim step between existing Su-30 models and an as-yet not fully specified fifth-generation offering from the Russian defense industry.

So what is actually new about the Su-35? Well, first, the new fighter features an improved airframe that promises a dramatically increased service life of 6,000 flight hours or 30 years of operation. Time between overhaul is to increase to 1,500 hours or 10 years in operation.

Aerodynamically, the Su-35 is similar to the existing Su-27 and unlike the more recent Su-30MKI, it does not have a canard. All three channels have an electrical fly-by-wire system without mechanical cabling.

The fully fly-by-wire fighter uses a new integrated control system, developed by Moscow-based MNPK Avionika, which simultaneously handles several systems, including remote control, automatic control and the braking system to enhance the
aircraft’s handling capability and maneuverability. Also absent from the Su-35 design is the overhead brake flap, which is a standard feature of the Su-27, with its functions performed instead by an active rudder.

The Su-35 chassis has been reinforced to support the aircraft’s increased takeoff and landing weights. For the same reason, the front bearing has two wheels.

Sukhoi’s new fighter is powered by a new 117S version of NPO Saturn’s earlier AL-31F powerplant to provide additional thrust. The engine features a new fan, high- and low-pressure systems and improved digital controls.

The upgrade has boosted the AL-31F’s maximum thrust rating by 16 percent to just under 32,000 pounds. In maximum, afterburner-free mode, it generates just over 19,000 pounds of thrust. The new engine, which is to be built by Ufa-based Motor Building Association (UMPO), also promises significantly improved reliability with mean time between overhaul tripled from 500 to 1,500 hours

New Onboard Systems

The Su-35’s cockpit features a new information management system, which integrates functional, logical, informational and software subsystems into a single core to facilitate the interaction between crew and equipment. The new unit includes two central digital computers and all-glass displays.

The core of Su-35 cockpit suite is a pair of two 9- by 12-inch, multifunction liquid-crystal displays; a multifunction panel with a built-in display processor; a wide-angle collimated display on the windshield and a control and indication panel.
The displays can show video images and on these it can overlay synthesized alphanumeric and other symbology. The cockpit computer also can produce and send digital video signals to a video recording unit.

The onboard systems and armaments for the Su-35 are controlled by buttons and switches on the joystick, from where the pilot can also activate engine controls. There are duplicate control buttons on the multi-function displays.

Eyes and Ears

The Su-35 also promises to be markedly stealthier than its Sukhoi predecessors. The fighter’s radar signature has been reduced both in the X-radio waveband and also in the angle range of plus or minus 60 degrees.

The core of the Su-35’s armaments package is a new radar control system with an Irbis-E phased-array antenna (Irbis-E). It was developed by V.V.Tikhomirov Instrument Research Institute and promises improved target detection capability.

The X-waveband multi-functional passive phased-array antenna (PPAA) radar is mounted on a two-step hydraulic drive unit (azimuth and roll). The antenna device scans via an electronically controlled beam in azimuth and angle of elevation in sectors not smaller than 60 degrees. The two-step electrohydraulic drive unit additionally turns the antenna by mechanical means to 60 degrees in azimuth and 120 degrees in roll.

The control system detects and tracks up to 30 air targets at a time, retaining continuity of space scanning and engaging up to eight targets simultaneously. The Irbis-E unit detects, selects and tracks up to four ground targets in several mapping modes with various resolutions at a range of almost 220 nm, without stopping to monitor the airspace. Over the same range, the radar can detect air targets with a radar cross section of just over 32 sq ft.

Other new onboard systems of Su-35 include modern navigation and radio communication packages and a new electronic countermeasures suite. Finally, the Su-35 is equipped with new types of air-to-air and air-to-surface missiles, including long-range weapons.