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German Aircraft Weapons
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Schräge Musik
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Schräge Musik, derived from the German colloquialism for "Jazz Music" was the name given to installations of upward-firing autocannon mounted in night fighters by the Luftwaffe and Imperial Japanese Navy Air Service during World War II, with the first victories for each occurring in May 1943.
This innovation allowed the night fighters to approach and attack British bombers from below, where they would be outside the bomber crew's field of view. Few bombers of that era carried defensive guns in the ventral position. The ventral turret fitted to some earlyAvro Lancasters was sighted by periscope from within the fuselage, and proved of little use. An attack by a Schräge Musik-equipped fighter was typically a complete surprise to the bomber crew, who would only realize 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. Experiments with upward firing guns in began in 1941. The first installation made late in 1942, was in a Dornier Do 17Z-10 that was also equipped with the early UHF-band version of the FuG 202 Lichtenstein BC radar. Bf 110s mounting a pair of MG FF/M 20 mm cannon in the rear compartment of the upper fuselage, firing through the canopy shot down a bomber in May 1943. From June 1943 on, an official conversion kit was produced for the Junkers Ju 88 and Dornier Do 217N fighters. Instead of approaching directly from the rear, they would approach about 1,500 ft (460 m) below the bomber. They would then pull up sharply and start firing when the nose of the bomber appeared in the gunsight. As the fighter slowed and the bomber passed over them, its wings were sprayed with cannon or machine gun rounds. This maneuver was effective, but difficult to perform. There was a significant risk of collision and if the bomb load exploded, it could take down the night fighter too. As new experimental aircraft were developed for the night fighter role, such as the Horten Ho 229, the Schräge Musik system was incorporated from the outset. The experimental Horten Ho 229 flying wing series had an unusual upward-firing armament proposed for testing on the V4 night fighter prototype, photoelectric fired vertically mounted rockets or recoilless guns instead of cannon armament inspired by the Jagdfaust system's design. Aircraft Mounts
Dornier Do 17Z-10 that was also equipped with the early UHF-band version of the FuG 202 Lichtenstein B/C radar served as a prototype. Conversion of three Dornier Do 217J-1s occurred in July 1942, to add a vertical armament of four or six MG 151s. Messerschmitt Bf 110s Schönert was made CO of II./NJG 5, and an armourer serving with the Gruppe, Oberfeldwebel Mahle, developed a working arrangement with the unit's Messerschmitt Bf 110s, mounting a pair of MG FF/M 20 mm (0.79 in) cannon in the rear compartment of the upper fuselage, firing through twin holes in the canopy's glazing. From June 1943, an official conversion kit was produced for the Junkers Ju 88 and Dornier Do 217N fighters.Between August 1943 and the end of the year, Schönert achieved 18 kills with the new gun installation. Jagerfaust Systems similar to the original Schräge Musik, such as the Sondergerät 500 or Jägerfaust, were tested on day fighters and other airframes, with the largest-calibre upward-firing aerial ordnance in German service, based on the quintuple-launcher of the 21 cm Nebelwerfer infantry barrage rocket, the experimental heavy-bomber based Grosszerstörer (heavy destroyer) also under test. The Jägerfaust system, firing 50 mm (2 in) projectiles vertically into the lower sides of bombers, was triggered by an optical device, so the pilot's only task was to pass beneath the target. This was tested on the Fw 190, and was destined for installation in the Me 163B and the Me 262B. The definitive night fighter version of the Messerschmitt Me 262, the Me 262B-2, was also designed to carry such an installation but the system was a failure and it was not used operationally. Trials with the Komet were promising, with six operational aircraft modified. On 10 April 1945, a Halifax bomber was shot down by Fritz Kelb flying a Jägerfaust-equipped Me 163B, most probably from I. Gruppe/JG 400 operating from Brandis, Germany. As experimental aircraft were developed as night fighters, such as the Horten Ho 229, a Schräge Musik system was incorporated from the outset. The experimental Horten Ho 229 flying wing series was proposed for consideration, with a form of unusual upward-firing armament for testing on the V4 night fighter prototype, photoelectric fired vertically mounted rockets or recoilless guns, instead of cannon armament inspired by the Jagdfaust. |
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Other Similar Systems
Schräge Musik was not a new idea and existed from WW I and similar systems were adopted by other nations in WW II.
World War I
During World War I, pusher-configured fighter aircraft with flexibly-mounted forward-firing machine guns (especially the Royal Aircraft Factory F.E.2 fighters), enabled gunners to discover the principle of zero-deflection shooting. For instance, when firing upward at 45° elevation, assuming the attacking aircraft and its target are travelling at about the same velocity and the range is fairly short, the trajectory will appear straight. The bullets' true path is of course a parabola, but due to the relative movement of the aircraft they appear to follow a straight line: so that accurate sighting of the weapon requires no deflection or 'aiming off'. This greatly simplifies the business of hitting a moving target from a moving weapon platform.
The pilots of Royal Aircraft Factory B.E.2 night fighters, after trying various schemes for attacking the Zeppelin raiders of 1915-16, hit on the idea of firing a mixture of explosive and incendiary bullets into the body of the airship from below. For this purpose a single .303 in (7.7 mm) air-cooled Lewis gun was mounted in front of the pilot’s cockpit, firing upward. Exploitation of the same zero-deflection concept described above led to the destruction of six German airships between September and December 1916. Later British night fighters were similarly armed with upward firing guns.
Several tractor-configured single-seat biplanes of the time featured machine guns mounted on the centre section of the top wing to fire over the disk of the propeller (thus bypassing the need for deflector plates or synchronization gears). Arrangements had to be made to reload these weapons to enable an exhausted magazine to be replaced with a full one. The Foster mounting was designed to allow a Lewis gun to be drawn down and tipped back to reload, using a quadrant shaped rail. Whether by accident or design, it was found that the mounting also allowed the gun to be held manually at an intermediate angle (typically and ideally about 45°) and fired upward, steadying the gun by holding its pistol grip and firing it with the "normal" trigger rather than the remote Bowden cable used for forward firing.
Again, once the "zero-deflection" principle was "re-discovered", it became common for the pilots of the Nieuport 11 and Nieuport 17 fighters, especially in British service, and Royal Aircraft Factory S.E.5s to exploit their Foster-mounted Lewis guns in this way, attacking enemy aircraft from the blind spot below the tail.
The Sopwith Dolphin, which entered service near the end of World War I, was armed with two forward-firing .303 in (7.7 mm) Vickers on the cowl, just forward of the cockpit; it could also carry a pair of .303 in (7.7 mm) Lewis guns on the forward cross-tube of the cabane strut structure, aimed forwards and upwards, and were so equipped on delivery from the makers. The Germans tried similar arrangements in 1917, when Gerhard Fieseler of Jasta 38 attached two machine guns to an Albatros D.V, pointing upwards and forwards.
Interwar Period
United Kingdom
The Boulton Paul Bittern was a twin-engined night fighter with an armament of barbette mounted guns, that could be angled upwards for attack against bombers, without having to enter a climb. The first of two Bittern prototypes flew in 1927, though performance was poor and the development stopped.
The Westland C.O.W. Gun Fighter (1930) and Vickers Type 161 (1931) were designed in response to Air Ministry specification F.29/27. This called for an interceptor fighter operating as a stable gun platform for the Coventry Ordnance Works 37 mm autocannon produced by the Coventry Ordnance Works (COW).
The COW gun had been developed in 1918 for use in aircraft and had been tested on the Airco DH.4. The cannon fired 23-ounce (0.65 kg) shells and was to be mounted at 45 deg or more above the horizontal. The tactic was to fly below the target bomber or airship and fire upwards into it. Gun firing trials with both types went well, with no detriment to airframe or performance, although the Westland prototype displayed "alarming" handling characteristics. Neither the Type 161 nor its competitor, the Westland C.O.W. Gun Fighter were ordered, and no more was heard of this use of the aerial COW gun.
Similar logic lay behind the later Vickers Type 414 twin-engined fighter. This aircraft, which can be seen a natural successor to the Vickers COW gun fighter, combined a streamlined monoplane two-seater fighter airframe with a remotely controlled nose-mounted 40mm cannon that could be elevated for no-allowance shooting.
The RAF put the Defiant into service in 1939, when moved into the night-fighter role it had some success, typically attacking from below and slightly ahead of the bomber, well outside its field of defensive fire.
USA
Bell YFM-1 Airacuda was designed as a "bomber-destroyer", touted as "... a mobile anti-aircraft platform."[7] Its armament included mainly forward-firing M4 37mm cannon, with an accompanying gunner mounted in a forward compartment of each of the two engine nacelles. Theoretically, the cannon could be slewed, aimed and fired at an oblique angle but flight tests and operational evaluation, disproved the theory: the type proved troublesome and except for initial flight testing in 1937, where full armament was carried, the nacelle cannon armament and the accompanying gunner–loaders were eliminated in the final development aircraft.
World War II
British Designs
Air Ministry Specification F.9/37 led to the second, Rolls-Royce Peregrine powered, prototype of the Gloster G39 having its armament installed at an angle of +12° for 'no-allowance' firing - three dorsal 20mm cannon in the fuselage and two in the nose.[9] While it was a promising aircraft in its own right, by the time that the second prototype was completed the conventionally-armed Bristol Beaufighter was already in production, so neither the G39 nor the subsequent Gloster Reaper were pursued.
Similar logic lay behind Air Ministry specification F11/37, which specified a turret-mounted cannon armament: of three companies who tendered (Armstrong Whitworth and Bristol) had turrets that could only traverse through the forward hemisphere, as did Air Ministry specification F22/39, written around the Vickers Type 414 twin-engined fighter, which combined a streamlined monoplane two-seater fighter airframe with a remotely controlled 40mm cannon in the nose that could be elevated for no-allowance[1] shooting.[5]
The Boulton Paul Defiant "turret fighter" was originally conceived under the F.9/35 specification for a "two-seat day and night fighter" to defend Great Britain against massed formations of unescorted enemy bombers.[9] Regardless of the requirement, the use of its dorsal turret was based on the "broadside" fighter interception and combined fighter attack tactic of bomber interception. Attempts to take on single-seat fighters with Defiants led to catastrophic results in 1940 over France and during the Battle of Britain.[27] With such high losses in day operations, the Defiant was transferred to night fighting and there the type achieved some success. Defiant night fighters typically attacked enemy bombers from below, in a similar manoeuvre to the later German Schräge Musik attacks, more often from slightly ahead or to one side, rather than from directly under the tail. During the Blitz on London of 1940–1941, the Defiant equipped four squadrons, shooting down more enemy aircraft than any other type.[28] The Defiant Mk II was fitted with AI.IV radar and a Merlin XX engine. A total of 207 Defiant Mk IIs were built but the Defiant was retired as radar-equipped Beaufighter and Mosquito night fighters entered service in 1941 and 1942.[29] Turret fighters with four 20mm cannon were specified under F.11/37 but got no further than a scaled prototype.[30]
A Douglas Havoc, BD126, was fitted with six upward firing machine guns in the fuselage behind the cockpit. The guns could be controlled in elevation from 30–50 degrees and 15 degrees in the azimuth by the gunner in the nose. The aircraft was tested at the A&AEE in 1941 and then by the GRU and Fighter Interception Unit.
Japan
In 1943, Commander Yasuna Kozono of the 251st Kōkūtai, Imperial Japanese Navy in Rabaul came up with the idea of converting the Nakajima J1N (J1N1-C) Irving into a night fighter. On 21 May 1943, at about the same time as the Luftwaffe's OberleutnantSchoenert had his first victory with Schräge Musik in Europe, the field-modified J1N1-C KAI shot down two B-17s of the 43rd Bomb Group who were attacking air bases around Rabaul. The Navy took immediate notice and placed orders with Nakajima, for the newly designated J1N1-S night fighter design. This model was christened the Model 11 Gekko (月光, Moonlight). It required only two crew and like the KAI, had a 20-millimetre (0.79 in)-calibre twinned pair of Type 99 Model 1 cannon firing upward and a second pair firing downward at a forward 30° angle, also placed in the fuselage behind the cabin. The Type 99 20mm calibre autocannon ordnance used by Japanese aircraft was based on the drum-magazine fed Swiss Oerlikon FF ordnance which was itself the basis for the Germans' own MG FF weapon, used to pioneer Schräge Musik for the Luftwaffe.
The Japanese Army Air Force Mitsubishi Ki-46 "Dinah" twin engined fighter was used to test the Schräge Musik armament format in its Ki-46 III KAI version in June 1943, using a 37 mm Ho-203 cannon with 200 rounds of ammunition, the largest calibre autocannon used for Schräge Musik-type operations. It was mounted in a similar position in the fuselage as the Luftwaffe's night fighters. Operational deployment began in October 1944.[24]
A Ki-45 fuselage with a Schräge Musik fitment, at the Udvar-Hazy Centermuseum
One of the main Japanese fighters using this device was the Kawasaki Ki-45 "Nick". With the Schräge Musik installation on the IJNAS's Nakajima J1N1-S "Gekko" (two or three 20mm cannons firing upwards, some had two firing downwards), the Nakajima C6N1-S "Myrt" single-engined, high-speed reconnaissance aircraft was used with a pair of 20 mm Type 99 cannons.[25]
One variant of the common A6M5 Zero single-seat fighter—the A6M5d-S—had a 20mm Type 99 cannon mounted just behind the pilot, firing upwards for night fighter combat.
USA
The American Northrop P-61 Black Widow night fighter could deliver a Schräge Musik-like surprise of its own, because of the design of its remote dorsal turret carrying a quartet of .50 Caliber Browning M2 machine guns, that could elevate to a full 90° position.
World War I
During World War I, pusher-configured fighter aircraft with flexibly-mounted forward-firing machine guns (especially the Royal Aircraft Factory F.E.2 fighters), enabled gunners to discover the principle of zero-deflection shooting. For instance, when firing upward at 45° elevation, assuming the attacking aircraft and its target are travelling at about the same velocity and the range is fairly short, the trajectory will appear straight. The bullets' true path is of course a parabola, but due to the relative movement of the aircraft they appear to follow a straight line: so that accurate sighting of the weapon requires no deflection or 'aiming off'. This greatly simplifies the business of hitting a moving target from a moving weapon platform.
The pilots of Royal Aircraft Factory B.E.2 night fighters, after trying various schemes for attacking the Zeppelin raiders of 1915-16, hit on the idea of firing a mixture of explosive and incendiary bullets into the body of the airship from below. For this purpose a single .303 in (7.7 mm) air-cooled Lewis gun was mounted in front of the pilot’s cockpit, firing upward. Exploitation of the same zero-deflection concept described above led to the destruction of six German airships between September and December 1916. Later British night fighters were similarly armed with upward firing guns.
Several tractor-configured single-seat biplanes of the time featured machine guns mounted on the centre section of the top wing to fire over the disk of the propeller (thus bypassing the need for deflector plates or synchronization gears). Arrangements had to be made to reload these weapons to enable an exhausted magazine to be replaced with a full one. The Foster mounting was designed to allow a Lewis gun to be drawn down and tipped back to reload, using a quadrant shaped rail. Whether by accident or design, it was found that the mounting also allowed the gun to be held manually at an intermediate angle (typically and ideally about 45°) and fired upward, steadying the gun by holding its pistol grip and firing it with the "normal" trigger rather than the remote Bowden cable used for forward firing.
Again, once the "zero-deflection" principle was "re-discovered", it became common for the pilots of the Nieuport 11 and Nieuport 17 fighters, especially in British service, and Royal Aircraft Factory S.E.5s to exploit their Foster-mounted Lewis guns in this way, attacking enemy aircraft from the blind spot below the tail.
The Sopwith Dolphin, which entered service near the end of World War I, was armed with two forward-firing .303 in (7.7 mm) Vickers on the cowl, just forward of the cockpit; it could also carry a pair of .303 in (7.7 mm) Lewis guns on the forward cross-tube of the cabane strut structure, aimed forwards and upwards, and were so equipped on delivery from the makers. The Germans tried similar arrangements in 1917, when Gerhard Fieseler of Jasta 38 attached two machine guns to an Albatros D.V, pointing upwards and forwards.
Interwar Period
United Kingdom
The Boulton Paul Bittern was a twin-engined night fighter with an armament of barbette mounted guns, that could be angled upwards for attack against bombers, without having to enter a climb. The first of two Bittern prototypes flew in 1927, though performance was poor and the development stopped.
The Westland C.O.W. Gun Fighter (1930) and Vickers Type 161 (1931) were designed in response to Air Ministry specification F.29/27. This called for an interceptor fighter operating as a stable gun platform for the Coventry Ordnance Works 37 mm autocannon produced by the Coventry Ordnance Works (COW).
The COW gun had been developed in 1918 for use in aircraft and had been tested on the Airco DH.4. The cannon fired 23-ounce (0.65 kg) shells and was to be mounted at 45 deg or more above the horizontal. The tactic was to fly below the target bomber or airship and fire upwards into it. Gun firing trials with both types went well, with no detriment to airframe or performance, although the Westland prototype displayed "alarming" handling characteristics. Neither the Type 161 nor its competitor, the Westland C.O.W. Gun Fighter were ordered, and no more was heard of this use of the aerial COW gun.
Similar logic lay behind the later Vickers Type 414 twin-engined fighter. This aircraft, which can be seen a natural successor to the Vickers COW gun fighter, combined a streamlined monoplane two-seater fighter airframe with a remotely controlled nose-mounted 40mm cannon that could be elevated for no-allowance shooting.
The RAF put the Defiant into service in 1939, when moved into the night-fighter role it had some success, typically attacking from below and slightly ahead of the bomber, well outside its field of defensive fire.
USA
Bell YFM-1 Airacuda was designed as a "bomber-destroyer", touted as "... a mobile anti-aircraft platform."[7] Its armament included mainly forward-firing M4 37mm cannon, with an accompanying gunner mounted in a forward compartment of each of the two engine nacelles. Theoretically, the cannon could be slewed, aimed and fired at an oblique angle but flight tests and operational evaluation, disproved the theory: the type proved troublesome and except for initial flight testing in 1937, where full armament was carried, the nacelle cannon armament and the accompanying gunner–loaders were eliminated in the final development aircraft.
World War II
British Designs
Air Ministry Specification F.9/37 led to the second, Rolls-Royce Peregrine powered, prototype of the Gloster G39 having its armament installed at an angle of +12° for 'no-allowance' firing - three dorsal 20mm cannon in the fuselage and two in the nose.[9] While it was a promising aircraft in its own right, by the time that the second prototype was completed the conventionally-armed Bristol Beaufighter was already in production, so neither the G39 nor the subsequent Gloster Reaper were pursued.
Similar logic lay behind Air Ministry specification F11/37, which specified a turret-mounted cannon armament: of three companies who tendered (Armstrong Whitworth and Bristol) had turrets that could only traverse through the forward hemisphere, as did Air Ministry specification F22/39, written around the Vickers Type 414 twin-engined fighter, which combined a streamlined monoplane two-seater fighter airframe with a remotely controlled 40mm cannon in the nose that could be elevated for no-allowance[1] shooting.[5]
The Boulton Paul Defiant "turret fighter" was originally conceived under the F.9/35 specification for a "two-seat day and night fighter" to defend Great Britain against massed formations of unescorted enemy bombers.[9] Regardless of the requirement, the use of its dorsal turret was based on the "broadside" fighter interception and combined fighter attack tactic of bomber interception. Attempts to take on single-seat fighters with Defiants led to catastrophic results in 1940 over France and during the Battle of Britain.[27] With such high losses in day operations, the Defiant was transferred to night fighting and there the type achieved some success. Defiant night fighters typically attacked enemy bombers from below, in a similar manoeuvre to the later German Schräge Musik attacks, more often from slightly ahead or to one side, rather than from directly under the tail. During the Blitz on London of 1940–1941, the Defiant equipped four squadrons, shooting down more enemy aircraft than any other type.[28] The Defiant Mk II was fitted with AI.IV radar and a Merlin XX engine. A total of 207 Defiant Mk IIs were built but the Defiant was retired as radar-equipped Beaufighter and Mosquito night fighters entered service in 1941 and 1942.[29] Turret fighters with four 20mm cannon were specified under F.11/37 but got no further than a scaled prototype.[30]
A Douglas Havoc, BD126, was fitted with six upward firing machine guns in the fuselage behind the cockpit. The guns could be controlled in elevation from 30–50 degrees and 15 degrees in the azimuth by the gunner in the nose. The aircraft was tested at the A&AEE in 1941 and then by the GRU and Fighter Interception Unit.
Japan
In 1943, Commander Yasuna Kozono of the 251st Kōkūtai, Imperial Japanese Navy in Rabaul came up with the idea of converting the Nakajima J1N (J1N1-C) Irving into a night fighter. On 21 May 1943, at about the same time as the Luftwaffe's OberleutnantSchoenert had his first victory with Schräge Musik in Europe, the field-modified J1N1-C KAI shot down two B-17s of the 43rd Bomb Group who were attacking air bases around Rabaul. The Navy took immediate notice and placed orders with Nakajima, for the newly designated J1N1-S night fighter design. This model was christened the Model 11 Gekko (月光, Moonlight). It required only two crew and like the KAI, had a 20-millimetre (0.79 in)-calibre twinned pair of Type 99 Model 1 cannon firing upward and a second pair firing downward at a forward 30° angle, also placed in the fuselage behind the cabin. The Type 99 20mm calibre autocannon ordnance used by Japanese aircraft was based on the drum-magazine fed Swiss Oerlikon FF ordnance which was itself the basis for the Germans' own MG FF weapon, used to pioneer Schräge Musik for the Luftwaffe.
The Japanese Army Air Force Mitsubishi Ki-46 "Dinah" twin engined fighter was used to test the Schräge Musik armament format in its Ki-46 III KAI version in June 1943, using a 37 mm Ho-203 cannon with 200 rounds of ammunition, the largest calibre autocannon used for Schräge Musik-type operations. It was mounted in a similar position in the fuselage as the Luftwaffe's night fighters. Operational deployment began in October 1944.[24]
A Ki-45 fuselage with a Schräge Musik fitment, at the Udvar-Hazy Centermuseum
One of the main Japanese fighters using this device was the Kawasaki Ki-45 "Nick". With the Schräge Musik installation on the IJNAS's Nakajima J1N1-S "Gekko" (two or three 20mm cannons firing upwards, some had two firing downwards), the Nakajima C6N1-S "Myrt" single-engined, high-speed reconnaissance aircraft was used with a pair of 20 mm Type 99 cannons.[25]
One variant of the common A6M5 Zero single-seat fighter—the A6M5d-S—had a 20mm Type 99 cannon mounted just behind the pilot, firing upwards for night fighter combat.
USA
The American Northrop P-61 Black Widow night fighter could deliver a Schräge Musik-like surprise of its own, because of the design of its remote dorsal turret carrying a quartet of .50 Caliber Browning M2 machine guns, that could elevate to a full 90° position.