4th generation fighters - fighters produced around 1970-1990s. Extensive use of BVR (beyond visual range) missiles, high powered radars, maneuverability, and are designed to achieve air superiority. Examples of 4th gen. fighters: F-15C, F-16, Su-27, Mig 29, Mirage 2000
5th generation fighters - 2005 to present. In order to qualify as a 5th generation fighter the aircraft MUST be stealth and usually features high powered radar like AESA radar, supermanuverability i.e. thrust vectoring, supercruise, and helmet mounted displays. Examples of 5th gen. fighters: F-22A Raptor, F-35 lightning II, Sukhoi PAK FA T-50
4.5 generation fighters - fighters produced 1990s to present. Aircraft that blend 4th and 5th generation technology such as AESA radar, thrust vectoring, helmet mounted displays, and feature a REDUCED radar cross section. This makes them significantly harder to detect with older 3rd and 4th generation fighters but they are still detectable with modern radars used in other 4.5 generation and 5th generation fighters. Examples of 4.5 gen. fighters: Dassault Rafale, Eurofighter Typhoon, F/A-18E Super Hornet, Su-35, JAS 39 Gripen, J-10
Are 4.5 Generation Fighters feasible?
"In this modern era of stealth combat, there are two kinds of fighters. Stealth fighters and targets." - Eric R. Branyan VP F-35 mission systems
Many nations around the world are in pursuit of 5th generation fighters. However, due to the enormous funds needed to produce 5th generation fighters and the use of advanced stealth technology many nations cannot develop 5th generation fighters. Thus, many countries have taken a "more balanced" approach by fielding 4.5 generation fighters which are designed to blend the best aspects of 4th and 5th generation fighters at a reasonable cost. The fundamental problem of 4.5 generation fighters are they will become obsolete within 5 to 10 years.
Many countries still purchase 4.5 generation fighters without any long term goal of acquiring 5th generation fighters. This will become problematic for many nations including Germany, France, Austria, and Spain. Within 5 to 10 years both the F-35 and T-50 will be in mass production and available to nations around the world which will make 4.5 generation fighters obsolete. At ranges of over 100 miles the 5th generation fighters will be able to gain missile lock on 4.5 generation fighters and destroy them without the 4.5 gen. fighters even knowing an enemy presence was in the area.
Many countries who are capable of gaining 5th generation fighters such as Germany continue to ignore the realization that 4.5 generation fighters will become obsolete. Germany could easily purchase F-35s but chooses to field the 4.5 generation Eurofighter Typhoon. The Eurofighter has an rcs (radar cross section) around 1m^2 compared to a normal fighter such as the F-15C which has an rcs of 5m^2. This may seem good comparatively but in reality against 5th generation fighters this is still detectable and large enough for advanced air to air missiles like the AIM-120D and R-77 Vympel to gain lock. The F-22A features an rcs of .0001-.0002m^2 (F-35 rcs is .0015m^2). No missile in the world could even come close to gaining lock on such as small target. This essentially means that 5th generation fighters will be able to engage 4.5 and 4th gen. fighters with impunity.
Many critics say that the high cost of 5th generation fighters make them unfeasible. Yet many 4.5 generation fighters cost almost as much or even more than the American F-35. For example, the Eurofighter costs 91.2 million dollars (63 million Euros exchange rate fluctuates keep that in mind) vs. the F-35 which will cost 83 million. The F-35 is a economical and exceptionally lethal strike aircraft. Current simulations show that the F-35 is at least 4 times more effective than existing 4th and 4.5 generation fighters in air to air combat. It doesn't make any sense to purchase 4.5 generation fighters if you can get a hold of 5th generation fighters which are significantly more effective and are in some cases cheaper. Unless of course you are some country like South Africa and have no neighbors that would have 5th generation technology any time soon.
The Future of 4th Generation Aircraft in the 21st Century
1. Dogfights of the Future . 2008. History Channel