A night fighter (later known as all-weather fighter or all-weather interceptor post-Second World War)Winchester 2006, p. 184. is a largely historical term for a fighter or interceptor aircraft adapted or designed for effective use at night, during periods of adverse meteorological conditions, or in otherwise poor visibility. Such designs were in direct contrast to day fighters: fighters and interceptors designed primarily for use during the day or during good weather. The concept of the night fighter was developed and experimented with during the First World War but would not see widespread use until WWII. The term would be supplanted by "all-weather fighter/interceptor" post-WWII, with advancements in various technologies permitting the use of such aircraft in virtually all conditions.
During the Second World War, night fighters were either purpose-built night fighter designs, or more commonly, heavy fighters or light bombers adapted for the mission, often employing radar or other systems for providing some sort of detection capability in low visibility. Many night fighters of the conflict also included instrument landing systems for landing at night, as turning on the runway lights made runways into an easy target for opposing intruders. Some experiments tested the use of day fighters on night missions, but these tended to work only under very favourable circumstances and were not widely successful. The war would see the first aircraft ever that was explicitly designed from the outset to function as a night fighter, the Northrop P-61 Black Widow.
Avionics systems were greatly miniaturised over time, allowing the addition of radar altimeter, terrain-following radar, improved instrument landing system, microwave landing system, Doppler weather radar, LORAN receivers, GEE, TACAN, inertial navigation system, GPS, and GNSS in aircraft. The addition of greatly improved landing and navigation equipment combined with radar led to the use of the term all-weather fighter or all-weather fighter attack, depending on the aircraft capabilities. The use of the term night fighter gradually faded away as a result of these improvements making the vast majority of fighters capable of night operation.
History
Early examples
At the start of the First World War, most combatants had little capability of flying at night, and little need to do so. The only targets that could be attacked with any possibility of being hit in limited visibility would be cities, an unthinkable target at the time. The general assumption of a quick war meant no need existed for strategic attacks.Cooper, Ralph, Jean-Claude Cailliez and Gian Picco. "Alfred Comte 1895–1965." earlyaviators.com, 19 November 2005. Retrieved: 15 April 2011.
Things changed on 22 September and 8 October 1914, when the Royal Naval Air Service bombed the production line and hangars of the Zeppelin facilities in Cologne and Düsseldorf.Madison, Rodney. "Air Warfare, Strategic Bombing". The Encyclopedia of World War I: A Political, Social and Military History, Volume 1, Spencer C. Tucker, ed. (Santa Barbara: ABC-CLIO, 2005), pp. 45–46. Although defences had been set up, all of them proved woefully inadequate. As early as 1915, a number of B.E.2c aircraft (the infamous "Fokker Fodder") were modified into the first night fighters. After lack of success while using darts and small incendiary bombs to attack Zeppelins from above, ultimately a Lewis gun loaded with novel incendiary ammunition, was mounted at an angle of 45° to fire upwards, to attack the enemy from below. This technique proved to be very effective.
After over a year of night Zeppelin raids, on the night of 2–3 September 1916, a BE2c flown by Captain William Leefe Robinson downed the SL 11, the first German airship to be shot down over Britain.. This action won the pilot a Victoria Cross and cash prizes totaling £3,500 put up by a number of individuals. This downing was not an isolated victory; five more German airships were similarly destroyed between October and December 1916, and caused the airship campaign to gradually be diminished over the next year with fewer raids mounted.Unikoski, Ari. "The War in the Air: Bombers: Germany, Zeppelins." firstworldwar.com, 22 August 2009. Retrieved: 13 April 2011.
Because of airships' limitations, the Luftstreitkräfte began to introduce long-range heavy bombers, starting with the Gotha G.IV aircraft that gradually took over the offensive. While their early daylight raids in May 1917 were able to easily evade the weak defenses of London, the strengthening of the home defence fighter force led to the Germans switching to night raids from 3 September 1917.Gray and Thetford 1962, p. 130. To counter night attacks, Sopwith Camel day fighters were deployed in the night fighter role. The Camels' Vickers guns were replaced by Lewis guns mounted over the wings, as the flash from the Vickers tended to dazzle the pilot when they were fired, and synchronised guns were considered unsafe for firing incendiary ammunition. Further modification led to the cockpit being moved rearwards. The modified aircraft were nicknamed the "Sopwith Comic".. To provide suitable equipment for Home Defence squadrons in the north of the UK, Avro 504K trainers were converted to night fighters by removing the front cockpit and mounting a Lewis gun on the top wing.Bruce 1965, pp. 35–36.
Interwar period With little money to spend on development, especially during the Great Depression, night-fighting techniques changed little until just prior to World War II.
In the meantime, aircraft performance had improved tremendously; compared to their First World War counterparts, modern bombers could fly about twice as fast, at over twice the altitude, with much greater bomb loads. They flew fast enough that the time between detecting them and the bombers reaching their targets left little time to launch interceptors to shoot them down. Higher altitude bombers also required extremely large and heavy antiaircraft guns to attack them, badly limiting the number of guns available. At night, or with limited visibility, these problems were compounded. The widespread conclusion was that "the bomber will always get through", and the Royal Air Force invested almost all of their efforts in developing a night bomber force, with the Central Flying School responsible for one of the most important developments in the period by introducing "blind flying" training.
The Spanish Republican Air Force used some Polikarpov I-15s as night fighters. Pilot José Falcó had equipped his fighter with a radio receiver for land-based guidance for interception. One of the I-15s configured for night operations, fitted with tracer and explosive .30 rounds, scored a daylight double victory against Bf 109s in the closing stages of the war.Lázaro, Carlos. "Los chatos noctumos" (in Spanish) Adar. Retrieved: 4 August 2013.
Nevertheless, some new technologies appeared to offer potential ways to improve night-fighting capability. During the 1930s, considerable development of infrared detectors occurred among all of the major forces, but in practice, these proved almost unusable. The only such system to see any sort of widespread operational use was the Spanner Anlage system used on the Dornier Do 17Z night fighters of the Luftwaffe. These were often also fitted with a large IR searchlight to improve the amount of light being returned.
Immediately prior to the opening of the war, radar was introduced operationally for the first time. Initially, these systems were unwieldy, and development of IR systems continued. Realizing that radar was a far more practical solution to the problem, Robert Watson-Watt handed the task of developing a radar suitable for aircraft use to 'Taffy' Bowen in the mid-1930s. In September 1937, he gave a working demonstration of the concept when a test aircraft was able to detect three Home Fleet capital ships in the North Sea in bad weather.
The promising implications of the test were not lost on planners, who reorganised radar efforts and gave them increased priority. This led to efforts to develop an operational unit for aircraft interception (AI). The size of these early AI radars required a large aircraft to lift them, and their complex controls required a multiperson crew to operate them. This naturally led to the use of light bombers as the preferred platform for aircraft interception radars, and in May 1939, the first experimental flight took place, on a Fairey Battle.
Second World War The war opened on 1 September 1939, and by this time, the RAF were well advanced with plans to build a radar – then called 'RDF' in Britain – equipped night-fighter fleet. The Aircraft Interception Mk. II radar (AI Mk. II) was being fitted experimentally to a small number of Bristol Blenheim aircraft, having been selected for this role as its fuselage was sufficiently roomy to accommodate the additional crew member and radar apparatus;. the first prototype system went into service in November 1939, long before the opening of major British operations. These early systems had significant practical problems, and while work was underway to correct these flaws, by the time the Blitz opened in August 1940, the night fighter fleet was still in its infancy.
Through this period, the RAF experimented with many other aircraft and interception methods in an effort to get a working night fighter force. One attempt to make up for the small number of working radars was to fit an AI to a Douglas Havoc bomber which also carried a searchlight in its nose. These Turbinlite aircraft were intended to find the targets and illuminate them with the searchlight, allowing Hurricanes adapted for night flying to shoot them down visually.Cotton, Frederick Sidney and William Helmore. "An improved method and means for intercepting night flying hostile aircraft." GB Patent 574970, 29 January 1946. This proved almost impossible to arrange in practice, and the Cat Eye fighters had little luck during the closing months of 1940. The Turbinlite squadrons were disbanded in early 1943.White, E. G. "1459 Flight and 538 Squadron." Nightfighter navigator. Retrieved: 1 August 2011.
By early 1941, the first examples of a production-quality radar, AI Mk. IV, were beginning to arrive. This coincided with the arrival of the Beaufighter, which offered significantly higher performance than the pre-war Blenheims; it was the highest performance aircraft capable of carrying the bulky early aircraft interception radars used for night fighter operations, and quickly became invaluable as a night fighter... Over the next few months, more and more Beaufighters arrived and the success of the night fighters roughly doubled every month until May, when the Luftwaffe ended their bombing efforts. Although night bombing never ended, its intensity was greatly decreased, giving the RAF time to introduce the AI Mk. VIII radar working in the microwave band, and the de Havilland Mosquito to mount it. This combination remained the premier night fighter until the end of the war.
As the German effort wound down, the RAF's own bombing campaign was growing. The Mosquitos had little to do over the UK, so a number of squadrons were formed within No. 100 Group RAF and fitted with special systems, such as Perfectos and Serrate, for homing-in on German night fighters. The British also experimented with mounting pilot-operated AI Mark 6 radar sets in single-seat fighters, and the Hurricane II C(NF), a dozen of which were produced in 1942, became the first radar-equipped, single-seat night fighter in the world. It served with 245 and 247 Squadrons briefly and unsuccessfully before being sent to India to 176 Squadron, with which it served until the end of 1943.Thomas 1996 A similarly radar-equipped Hawker Typhoon was also developed, but no production followed.