is a late-war Japanese prototype aircraft that was intended to be used as an interceptor to counter squadrons of
Boeing B-29 Superfortress bombers. The first interceptor squadrons were formed during
World War I to defend
London against attacks by
Zeppelins and later against fixed-wing long-range
bombers. Early units generally used aircraft withdrawn from front-line service, notably the
Sopwith Pup. They were told about their target's location before take-off from a command centre in the
Horse Guards building. The Pup proved to have too low performance to easily intercept
Gotha G.IV bombers, and the superior
Sopwith Camels supplanted them. The term "interceptor" was in use by 1929. Through the 1930s, bomber aircraft speeds increased so much that conventional interceptor tactics appeared impossible. Visual and acoustic detection from the ground had a range of only a few miles, which meant that an interceptor would have insufficient time to climb to altitude before the bombers reached their targets. Standing
combat air patrols were possible but only at great cost. The conclusion at the time was that "
the bomber will always get through". The invention of
radar made possible early, long-range detection of aircraft on the order of , both day and night and in all weather. A typical bomber might take twenty minutes to cross the detection zone of early radar systems, time enough for interceptor fighters to start up, climb to altitude and engage the bombers.
Ground controlled interception required constant contact between the interceptor and the ground until the bombers became visible to the pilots and nationwide networks like the
Dowding system were built in the late 1930s to coordinate these efforts. During
World War II the effectiveness of interceptor aircraft meant that bombers often needed to be escorted by long range fighter aircraft. Many aircraft were able to be fitted with
Aircraft interception radar, further facilitating the interception of enemy aircraft. The introduction of jet power increased flight speeds from around to around in a step and roughly doubled operational altitudes. Although radars also improved in performance, the gap between offense and defense was dramatically reduced. Large attacks could so confuse the defense's ability to communicate with pilots that the classic method of manual ground controlled interception was increasingly seen as inadequate. In the United States, this led to the introduction of the
Semi-Automatic Ground Environment to computerize this task, while in the UK it led to enormously powerful radars to improve detection time.
air superiority fighter intercepting a Russian
Tu-95 near
AlaskaThe introduction of the first useful
surface to air missiles in the 1950s obviated the need for fast reaction time interceptors as the missile could launch almost instantly. Air forces increasingly turned to much larger interceptor designs, with enough fuel for longer endurance, leaving the point-defense role to the missiles. This led to the abandonment of a number of short-range designs like the
Avro Arrow and
Convair F-102 in favor of much larger and longer-ranged designs like the
North American F-108 and
MiG-25. In the 1950s and 1960s during the
Cold War, a strong interceptor force was crucial for the opposing
superpowers as it was the best means to defend against an unexpected nuclear attack by
strategic bombers. Hence, for a brief period of time they fared rapid development in both speed, range, and altitude. At the end of the 1960s, a nuclear attack became unstoppable with the introduction of ballistic missiles capable of approaching from outside the atmosphere at speeds as high as . The doctrine of
mutually assured destruction replaced the trend of defense strengthening, making interceptors less strategically logical. The utility of interceptors waned as the role merged with that of the heavy
air superiority fighter. The interceptor mission is, by its nature, a difficult one. Consider the desire to protect a single target from attack by long-range bombers. The bombers have the advantage of being able to select the parameters of the mission – attack vector, speed and altitude. This results in an enormous area from which the attack can originate. In the time it takes for the bombers to cross the distance from first detection to being on their targets, the interceptor must be able to start, take off, climb to altitude, maneuver for attack and then attack the bomber. A dedicated interceptor aircraft sacrifices the capabilities of the
air superiority fighter and
multirole fighter (i.e., countering enemy fighter aircraft in
air combat manoeuvring), by tuning its performance for either fast climbs or high speeds. The result is that interceptors often look very impressive on paper, typically outrunning, outclimbing and outgunning slower fighter designs. However, pure interceptors fare poorly in
fighter-to-fighter combat against the same "less capable" designs due to limited maneuverability especially at low altitudes and speeds.
Point-defense interceptors English Electric Lightning point defense interceptor In the spectrum of various interceptors, one design approach especially shows sacrifices necessary to achieve decisive benefit in a chosen aspect of performance. A "point defense interceptor" is of a lightweight design, intended to spend most of its time on the ground located at the defended target, and able to launch on demand, climb to altitude, manoeuvre and then attack the bomber in a very short time, before the bomber can deploy its weapons. At the end of Second World War, the
Luftwaffes most critical requirement was for interceptors as the Commonwealth and American air forces pounded German targets night and day. As the bombing effort grew, notably in early 1944, the Luftwaffe introduced a rocket-powered design, the
Messerschmitt Me 163 Komet, in the very-short-range interceptor role. The engine allowed about 7 minutes of powered flight, but offered such tremendous performance that they could fly right by the defending fighters. The Me 163 required an airbase, however, which were soon under constant attack. Following the
Emergency Fighter Program, the Germans developed even odder designs, such as the
Bachem Ba 349 Natter, which launched vertically and thus eliminated the need for an airbase. In general all these initial German designs proved difficult to operate, often becoming death traps for their pilots, SAM advancements ended the concept of massed high-altitude bomber operations, in favor of
penetrators (and later
cruise missiles) flying a combination of techniques colloquially known as "flying below the radar". By flying
terrain masking low-altitude
nap-of-the-earth flight profiles the effective range, and therefore reaction time, of ground-based radar was limited to at best the
radar horizon. In the case of ground radar systems this can be countered by placing radar systems on mountain tops to extend the radar horizon, or through placing high performance radars in interceptors or in AWACS aircraft used to direct point defense interceptors.
Area defense As capabilities continued to improve – especially through the widespread introduction of the
jet engine and the adoption of high speed, low level flight profiles, the time available between detection and interception dropped. Most advanced point defence interceptors combined with long-range radars were struggling to keep the reaction time down enough to be effective. Fixed times, like the time needed for the pilot to climb into the cockpit, became an increasing portion of the overall mission time, there were few ways to reduce this. During the
Cold War in times of heightened tensions,
quick reaction alert (QRA) aircraft were kept piloted, fully fueled and armed, with the engines running at idle on the runway ready to take off. The aircraft being kept topped up with fuel via hoses from underground fuel tanks. If a possible intruder was identified, the aircraft would be ready to take off as soon as the external fuel lines were detached. However, keeping QRA aircraft at this state of readiness was physically and mentally draining to the pilots and was expensive in terms of fuel. As an alternative, longer-range designs with extended loiter times were considered. These
area defense interceptors or
area defense fighters were in general larger designs intended to stay on lengthy patrol and protect a much larger area from attack, depending on greater detection capabilities, both in the aircraft themselves and operating with AWACS, rather than high speed to reach targets. The exemplar of this concept was the
Tupolev Tu-28. The later
Panavia Tornado ADV was able to achieve long range in a smaller airframe through the use of more efficient engines. Rather than focusing on acceleration and climb rate, the design emphasis is on range and missile carrying capacity, which together translate into combat endurance,
look-down/shoot-down radars good enough to detect and track fast moving
interdictors against
ground clutter, and the capability to provide guidance to
air-to-air missiles (AAM) against these targets. High speed and acceleration was put into long-range and medium-range AAMs, and agility into short range dog fighting AAMs, rather than into the aircraft themselves. They were first to introduce all-weather
avionics, assuring successful operations during night, rain, snow, or fog. Countries that were strategically dependent on surface fleet, most notably US and UK, maintained also
fleet defense fighters, such as the
F-14 Tomcat. ==Development==