The fighter Aircraft are classified as generations according to their Design, Avionics and weapon system. Thus we have five generations of fighter aircraft and sixth generation fighter aircraft are in testing phase. When we invent something new that can be used in fighter aircraft but cannot be upgraded on the existing aircraft then we design a new aircraft with this new invention that forms a new generation of Aircraft.
FIRST GENERATION (1942-1950)
First generation aircraft are developed at the time of end of world war two.They replaced the propeller powered fighters to jet powered fighters. They had high subsonic speed than the propeller aircraft and had efficient performance at high altitudes and they were using straight wing because at that time other type of wings were not discovered.
SECOND GENERATION (1950-1960)
Even though the first generation had jet engines their primary weapon is a machine gun and it needs a radar operator to guide the aircraft in the night and foggy situations. The second generation aircraft came with air to air (Infrared heat seeker) missile as their primary weapon and they were using various wing shapes like swept wing, delta wing and some changes in fuselage design (area rule). The second generation aircraft were using turbofan engine so they did fly above the speed of sound, these are the first aircraft in the history to brake the sound barrier.They had inbuilt radar to detect other aircraft which were in out of visible range.
EXAMPLE: HAL HF 24 MARUT
THIRD GENERATION (1960-1975)
Because of the second generation aircraft the sky become shrank, so the next generation aircraft had high maneuverability and high speed with the addition of afterburner in the turbofan engine and variable wings. The third generation aircraft also had air to surface guided missile and laser guided missile in it’s weapon list.The second generation stem powered aircraft controls and instruments are replaced with analog avionics. They had increased range and payload capabilities.
EXAMPLE: MIG 21
FOURTH GENERATION (1975-2005)
The fourth generation aircraft are the one using digital avionics. Fly by wire system is introduced in this aircraft that led to the high performance of the aircraft. To reduce the money spend for the production of the aircraft multirole combat aircraft were introduced, A single multirole combat aircraft can do air superiority, ground attack, bombing, intercepting, striking etc.The fourth generation aircraft have on board mini computers to assist the pilot for safe and economic flight. This generation aircraft have Relaxed flight ability that means this aircraft can retain from disturbed position to stable position by itself with the help of on board avionics. Some of this fourth generation aircraft were designed to do vertical takeoff and landing by thrust vectoring but this vertical maneuvers are not fuel efficient so it did not get used broadly.
EXAMPLE: HAL TEJAS
FIFTH GENERATION (ONGOING)
This fifth generation aircraft are stealth multirole fighters. Stealth aircraft have ability to fly without detected by the Radar.Their structures are made of some materials , this materials can emit or distract radar waves to hide from the enemy radar. Also the fifth generation aircraft have ability to do supercruise (Cruising at supersonic speed), advanced avionics to networked data fusion from various sensor and radars for self awareness.
EXAMPLE: HAL AMCA, HAL FGFA
Sixth generation aircraft are under research phase, they believed to be have ability to fly at hypersonic speed.