Night Fighter Aircraft
http://www.militaryfactory.com/aircraft/nightfighter-aircraft.aspNight fighters began to be used in World War I and included types that were specifically modified to operate at night.
During World War II, night fighters were either purpose-built or day fighters modified to be effective night fighting combat aircraft, often employing radar or other systems for providing some sort of detection capability in low visibility. Many WW II night fighters also included instrument landing systems for landing at night as turning on the runway lights made runways into an easy target for opposing intruders.
Avionics systems were greatly miniaturized over time allowing the addition of radar altimeter, terrain-following radar, improved instrument landing system (ILS), microwave landing system (MLS), Doppler weather radar, LORAN receivers, GEE, tactical air navigation system (TACAN), inertial navigation system (INS), 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.
The Nazis invaded Poland 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 Airborne Interception Mk. II radar (AI Mk. II) was being fit 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 flaw, 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. 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.
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 airborne 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 '41, 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 fit 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. A similarly radar-equipped Hawker Typhoon was also developed, but no production followed.
Luftwaffe instrument landing system indicator, built 1943
German airborne interception radar efforts at this point were about two years behind the British. Unlike in Britain, where the major targets lay only a few minutes' flight time from the coast, Germany was protected by large tracts of neutral territory that gave them long times to deal with intruding bombers. Instead of airborne radar, they relied on ground-based systems; the targets would first be picked up by radar assigned to a "cell", the radar would then direct a searchlight to "paint" the target, allowing the fighters to attack them without on-board aids. The searchlights were later supplanted with short-range radars that tracked both the fighters and bombers, allowing ground operators to direct the fighters to their targets. By July 1940, this system was well developed as the Kammhuber Line, and proved able to deal with the small raids by isolated bombers the RAF was carrying out at the time.
At the urging of R.V. Jones, the RAF changed their raid tactics to gather all of their bombers into a single "stream". This meant that the ground-based portion of the system was overwhelmed; with only one or two searchlights or radars available per "cell", the system was able to handle perhaps six interceptions per hour. By flying all of the bombers over a cell in a short period, the vast majority of the bombers flew right over them without ever having been plotted, let alone attacked. German success against the RAF plummeted, reaching a nadir on 30/31 May 1942, when the first 1,000-bomber raid attacked Cologne, losing only four aircraft to German night fighters.
German airborne interception radar efforts at this point were about two years behind the British. Unlike in Britain, where the major targets lay only a few minutes' flight time from the coast, Germany was protected by large tracts of neutral territory that gave them long times to deal with intruding bombers. Instead of airborne radar, they relied on ground-based systems; the targets would first be picked up by radar assigned to a "cell", the radar would then direct a searchlight to "paint" the target, allowing the fighters to attack them without on-board aids. The searchlights were later supplanted with short-range radars that tracked both the fighters and bombers, allowing ground operators to direct the fighters to their targets. By July 1940, this system was well developed as the Kammhuber Line, and proved able to deal with the small raids by isolated bombers the RAF was carrying out at the time.
At the urging of R.V. Jones, the RAF changed their raid tactics to gather all of their bombers into a single "stream". This meant that the ground-based portion of the system was overwhelmed; with only one or two searchlights or radars available per "cell", the system was able to handle perhaps six interceptions per hour. By flying all of the bombers over a cell in a short period, the vast majority of the bombers flew right over them without ever having been plotted, let alone attacked. German success against the RAF plummeted, reaching a nadir on 30/31 May 1942, when the first 1,000-bomber raid attacked Cologne, losing only four aircraft to German night fighters.
The Ju 88R-1 night fighter captured by the RAF in April 1943
A restored Bf 110G night fighter with the VHF-band SN-2 radar antennae
In 1942, the Germans first started deploying the initial B/C low UHF-band version of the Lichtenstein radar, and in extremely limited numbers, using a 32-dipole element Matratze (mattress) antenna array. This late date, and slow introduction, combined with the capture of a Ju 88R-1 night fighter equipped with it in April 1943 when flown to RAF Dyce, Scotland, by a defecting Luftwaffe crew, allowed British radio engineers to develop jamming equipment to counter it. A race developed with the Germans attempting to introduce new sets and the British attempting to jam them. The early Lichtenstein B/C was replaced by the similar UHF-band Lichtenstein C-1, but when the German night fighter defected and landed in Scotland in April 1943, that radar was quickly jammed. The low VHF-band SN-2 unit that replaced the C-1 remained relatively secure until July 1944, but only at the cost of using huge, eight-dipole element Hirschgeweih (stag's antlers) antennae that slowed their fighters as much as 25 mph, making them easy prey for British night fighters that had turned to the offensive role. The capture in July 1944 of a Ju 88G-1 night fighter of NJG 2 equipped with an SN-2 Lichtenstein set, flown by mistake into RAF Woodbridge, revealed the secrets of the later, longer-wavelength replacement for the earlier B/C and C-1 sets.
The Luftwaffe also used single-engined aircraft in the night-fighter role, starting in 1939 with the Arado Ar 68 and early Messerschmitt Bf 109 models, which they later referred to as Wilde Sau (wild boar). In this case, the fighters, typically Focke-Wulf Fw 190s, were equipped only with a direction finder and landing lights to allow them to return to base at night. For the fighter to find their targets, other aircraft, which were guided from the ground, would drop strings of flares in front of the bombers. In other cases, the burning cities below provided enough light to see their targets. Messerschmitt Bf 109G variants had G6N and similar models fitted with FuG 350 Naxos "Z" radar receivers for homing in on the 3-gigahertz band H2S emissions of RAF bombers – the April 1944 combat debut of the American-designed H2X bomb-aiming radar, operating at a higher 10 GHz frequency for both RAF Pathfinder Mosquitos and USAAF B-24 Liberators that premiered their use over Europe, deployed a bombing radar that could not be detected by the German Naxos equipment. The Bf 109G series aircraft fitted with the Naxos radar detectors also were fitted with the low- to mid-VHF band FuG 217/218 Neptun active search radars, as were Focke-Wulf Fw 190 A-6/R11 aircraft: these served as radar-equipped night-fighters with NJGr 10 and NJG 11. A sole Fw 190 A-6 Wk.Nr.550214 fitted with FuG 217 is a rare survivor.[31]
The effective Schräge Musik [N 4] offensive armament fitment was the German name given to installations of upward-firing autocannon mounted in large, twin-engined night fighters by the Luftwaffe and both the Imperial Japanese Navy Air Service and Imperial Japanese Army Air Service during World War II, with the first victories for the Luftwaffe and IJNAS each occurring in May 1943. This innovation allowed the night fighters to approach and attack bombers from below, where they were outside the bomber crew's field of view. Few bombers of that era carried defensive guns in the ventral position. An attack by a Schräge Musik-equipped fighter was typically a complete surprise to the bomber crew, who would only realise that a fighter was close by when they came under fire. Particularly in the initial stage of operational use until early 1944, the sudden fire from below was often attributed to ground fire rather than a fighter.
Rather than nighttime raids, the US Army Air Forces were dedicated to daytime bombing over Germany and Axis allies, that statistically were much more effective.[33] The British night-bombing raids showed a success rate of only one out of 100 targets successfully hit.[34][page needed] At the urging of the British, who were looking to purchase US-made aircraft, US day fighters were initially adapted to a night role, including the Douglas P-70 and later Lockheed P-38M "Night Lightning". The only purpose-built night fighter design deployed during the war, the American Northrop P-61 Black Widow was introduced first in Europe and then saw action in the Pacific, but it was given such a low priority that the British had ample supplies of their own designs by the time it was ready for production. The first USAAF unit using the P-61 did not move to Britain until February 1944; operational use did not start until the summer, and was limited throughout the war. Colonel Winston Kratz, director of night-fighter training in the USAAF, considered the P-61 as adequate in its role, "It was a good night fighter. It did not have enough speed".
The U.S. Navy was forced into the night-fighting role when Japanese aircraft successfully harassed their units on night raids. The Japanese Navy had long screened new recruits for exceptional night vision, using the best on their ships and aircraft instead of developing new equipment for this role. To counter these raids, the Navy fitted microwave-band, compact radar sets to the wings of its single-engined Grumman F6F Hellcat and Vought F4U Corsair fighters by the close of the war, operating them successfully in the Pacific. In several cases these aircraft were used on raids of their own.
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