Aday fighter is afighter aircraft equipped only to fight during the day. More specifically, it refers to a multi-purpose aircraft that does not include equipment for fighting at night (such as aradar and specializedavionics),[1] although it is sometimes used to refer to someinterceptors as well.
The term is an example of aretronym: before the development of effective dedicatednight fighter aircraft early inWorld War II, in effect, all fighter aircraft that were not specifically modified for night combat were day fighters.
Examples of planes that were classified as day fighters were theSupermarine Spitfire[2] andMesserschmitt Bf 109. Both were excellent interceptors, but were also found in roles such asfighter-bomber andreconnaissance. However, the weight of the radar systems needed to effectively track down enemy bombers at night was such that these smaller aircraft simply couldn't carry them given the electronics of the day. This led to the use of twin-engine aircraft like theBristol Beaufighter andMesserschmitt Bf 110 as dedicatednight fighters, at which point the term day fighter began to be used.
Some lighter designs like theHawker Hurricane andFocke-Wulf Fw 190 were also adapted to night fighting after a fashion, lacking radar and relying onsearchlights or fires on the ground to illuminate their targets. These were preferred over the Spitfire and Bf 109 largely due to their wide-tracklanding gear, which made landing at night somewhat safer. Although such designs were in service throughout the war, they proved to have little real effectiveness compared to the dedicated night fighter designs.
Late in the war the considerable advances in radar technology, notably the introduction of thecavity magnetron, allowed for much smaller radar sets. At the same time, aircraft engines had roughly doubled in performance over the same period. This led to the late-war introduction of single-engine night fighters like theGrumman F6F,Vought F4U, as well as more agile twin-engine planes such as theLockheed P-38, with some success.
As the size and weight of night-fighting equipment remained considerable in comparison to airframe size and engine power, the day fighter remained a part of front-line air forces into the 1960s. In the immediate post-war era, designs like theNorth American F-86 Sabre,[3]Mikoyan-Gurevich MiG-15 andHawker Hunter typified the day-fighter role. These were followed by similarsupersonic designs in the early 1960s, including theLockheed F-104 Starfighter andMikoyan-Gurevich MiG-21.
However, as the size of basic fighters grew, along with their engine power, the relative cost of carrying night-fighting equipment fell until most designs carried such equipment. Lightweight fighters without full night equipment such as theF-5 Freedom Fighter/Tiger II are still used by nations that lack the money to acquire advanced fighter aircraft.
The last of the purpose-designed day fighters were the original AmericanGeneral Dynamics F-16 Fighting Falcon and theNorthrop YF-17 that competed for theLightweight Fighter contract, which had the goal of providing the USAF with an inexpensive day fighter that could be purchased in great numbers to establish air superiority. The designs originated in a mid-1960s effort known as the "Advanced Day Fighter". After winning the contract the F-16 quickly matured into a much more capable multi-role aircraft and can no longer be considered a day fighter. Likewise, the YF-17 evolved into the much largerMcDonnell Douglas F/A-18 Hornet andBoeing F/A-18E/F Super Hornet, which is used in the 2010s by the United States Navy as the primary all-weather combat aircraft.