page_title: Fourth-generation jet fighter
section_title: Avionics
hierarchical_section_title: Fourth-generation jet fighter / Design considerations / Avionics
caption_attribution_description: English: Optical radar station for Su aircraft. MAKS-2009 Русский: Оптическая локационная станция для самолётов Су. МАКС-2009
context_page_description: Fourth-generation jet fighter is a general classification of jet fighters in service from approximately 1980 to the present and represent design concepts of the 1970s. Fourth-generation designs are heavily influenced by lessons learned from the previous generation of combat aircraft. Long-range air-to-air missiles, originally thought to make dogfighting obsolete, proved less influential than expected, precipitating a renewed emphasis on maneuverability. Meanwhile, the growing costs of military aircraft in general and the demonstrated success of aircraft such as the F-4 Phantom II gave rise to the popularity of multirole combat aircraft in parallel with the advances marking the so-called fourth generation.
  During the period in question, maneuverability was enhanced by relaxed static stability, made possible by introduction of the fly-by-wire flight control system, which in turn was possible due to advances in digital computers and system-integration techniques. Replacement of analog avionics, required to enable FBW operations, became a fundamental requirement as legacy analog computer systems began to be replaced by digital flight control systems in the latter half of the 1980s.
context_section_description: Avionics is a catch-all term for the electronic systems aboard an aircraft, which have been growing in complexity and importance. The main elements of an aircraft's avionics are its communication and navigation systems, sensors (radar and IR), computers and data bus, and user interface. Because they can be readily swapped out as new technologies become available, they are often upgraded over the lifetime of an aircraft. A number of F-15C Eagles, the type was first produced in 1978, have received upgrades in the 2007 such as AESA radar and Joint Helmet Mounted Cueing System and will receive the 2040C Eagle upgrade to keep them in service until 2040, thanks to its large size and long airframe life.
  Details about these systems are highly classified. Thus, many export aircraft have downgraded avionics, and buyers often replace them with domestically developed avionics, sometimes considered superior to the original. Examples are the Sukhoi Su-30MKI sold to India, the F-15I and F-16I sold to Israel, and the F-15K sold to South Korea.
  The primary sensor for all modern fighters is radar. The U.S. fielded its first modified F-15Cs equipped with AN/APG-63(V)2 Active electronically scanned array radars, which have no moving parts and are capable of projecting a much tighter beam and quicker scans. Later on, it was introduced to the F/A-18E/F Super Hornet and the block 60 (export) F-16 also, and will be used for future American fighters. France introduced its first indigenous AESA radar, the  RBE2-AESA built by Thales in February 2012 for use on the Rafale. The RBE2-AESA can also be retrofitted on the Mirage 2000. A European consortium GTDAR is developing an AESA Euroradar CAPTOR radar for future use on the Typhoon. Russia has an AESA radar on its MIG-35 and their newest Su-27 versions. For the next-generation F-22 and F-35, the U.S. will use low probability of intercept (LPI) capacity. This will spread the energy of a radar pulse over several frequencies, so as not to trip the radar warning receivers that all aircraft carry.
  In response to the increasing American emphasis on radar-evading stealth designs, Russia turned to alternate sensors, with emphasis on infra-red search and track (IRST) sensors, first introduced on the American F-101 Voodoo and F-102 Delta Dagger fighters in the 1960s, for detection and tracking of airborne targets. These measure IR radiation from targets. As a passive sensor, it has limited range, and contains no inherent data about position and direction of targets - these must be inferred from the images captured. To offset this, IRST systems can incorporate a laser rangefinder in order to provide full fire-control solutions for cannon fire or for launching missiles. Using this method, German MiG-29 using helmet-displayed IRST systems were able to acquire a missile lock with greater efficiency than USAF F-16 in wargame exercises. IRST sensors have now become standard on Russian aircraft. With the exception of the F-14D (officially retired as of September 2006), no 4th-generation Western fighters carry built-in IRST sensors for air-to-air detection, though the similar FLIR is often used to acquire ground targets.
  However '4.5 generation' fighters started introducing integrated IRST systems, such as the Dassault Rafale boasting the Optronique secteur frontal integrated IRST, a feature adopted very early in its design as an "omnirole" fighter jet. The Eurofighter Typhoon introduced the PIRATE-IRST (beginning with Tranche 1 Block 5 aircraft, while previously build aircraft are being retrofitted since spring 2007) and the F-35s will have built-in, PIRATE-IRST sensors, a feature adopted early in the design, meanwhile beginning in 2012 the Super Hornet will also have an IRST.
  The tactical implications of the computing and data bus capabilities of aircraft are hard to determine. A more sophisticated computer bus would allow more flexible uses of the existing avionics. For example, it is speculated that the F-22 is able to jam or damage enemy electronics with a focused application of its radar. A computing feature of
caption: The OLS-30 is a combined IRST/LR device.
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