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G7a torpedo

April 09, 2024

The G7a(TI) was the standard issue Kriegsmarine torpedo introduced to service in 1934. It was a steam-powered design, using a wet heater engine burning decaline, with a range of 7,500 metres (24,600 ft) at 40 knots (74 km/h; 46 mph) speed. In 1936, the Kriegsmarine's first electrical powered torpedo was introduced with the G7e(TII). It was replaced beginning in 1942 by the G7e(TIII). The G7a(TI) remained in service as the main torpedo of Kriegsmarine for the length of the war, being the only torpedo used from surface vessels, and alongside electric torpedoes on the uboats.

German G7a(TI) torpedo at the Norwegian Armed Forces Museum in Oslo

Design edit

The G7a(TI) torpedo was 533.4 mm (21.00 in) in diameter, 7,163 millimetres (23 feet 6.0 inches) in length (with a type Ka or Kb warhead and Pi1 or Pi2 pistol), the warhead holding a charge of approximately 280 kg (620 lb) of so-called Schießwolle 36. It was Kriegsmarine's first operational torpedo (hence "TI" = Torpedo number one), and the standard issue torpedo for all German U-boats and surface torpedo-bearing vessels from 1934 to the end of WW2.

 
The GA VIII gyroscope, as used in the G7a(TI) torpedo

The torpedo was a straight-running unguided design, controlled by a gyroscope. The TI had variable speed, running a distance of 5,000 m at 81 km/h (5,500 yd at 44kt), 7,500 m at 74 km/h (8,250 yd at 40 kt), and 12,000 m at 55.6 km/h (13,200 yd at 30 kt). The 44 kt setting was used only by torpedo boats like the Schnellboote on torpedoes with a reinforced engine.

The TI was the last naval torpedo of German design in operational use with the traditional standard wet heat method of propulsion. The torpedo was powered by an engine fed by a mixture of compressed air and steam. Decaline fuel was burning in a combustion chamber, creating steam from fresh water. The torpedo's speed was determined by the level of pressure (three settings for 30/40/44 kn) from the low-pressure regulator feeding air to the bottom of the combustion chamber. The resulting superheated steam powered a four cylinder reciprocating engine, in turn powering a pair of contra-rotating propellers.

Though this system of propulsion gave the TI great speed and endurance it had the distinct disadvantage of being very noisy and leaving a long wake of bubbles, common to most torpedoes of the period, with the exception of the Japanese surface-launched Type 93 and submarine-launched Type 95, which were fuelled by an enriched oxygen wetheater engine. For U-boats, this relegated the TI for use mainly at night, when its wake was least noticeable, so as to not give away the element of surprise and the location of the submarine that fired it. During daytime, the electrical propulsioned torpedoes were favoured.

For the period 1934-1940 the only available warhead for the TI and TII were the Type Ka, with two available pistols: The Pi G7A-AZ and the Pi G7a-MZ. The former was a direct-acting mechanical pistol, while the latter had an additional influence-mechanism (magnetic). Both mechanisms were flawed and contributed to the german "Torpedokrise"(torpedo crisis) which lasted from the start of the war and through 1942. The mechanical deflection arms was designed too short, and the magnetic igniting-mechanism couldn't be properly tuned for the natural magnetic fields in the northern hemisphere and narrow fiords. These issues led to premature or late detonations, as well as failing to detonate even when hitting the target, in numerous cases during this period until properly working pistols were introduced with first the mechanical Pi1, and later the combined mechanical/magnetic Pi2. Also, the depth mechanism had a design-issue leading to leakage of vacuum when stored on the U-boats, causing the torpedo to run deep. The problems were common for the TI and TII torpedoes, but the TI also had issues with weak engine blocks (cracking at 44 kt setting), and the TII had issues with poorly performing batteries.

The problems were so serious, Admiral Dönitz said, "...never before in military history has a force been sent into battle with such a useless weapon."[1] In general, all issues were resolved by 1942 when new depth mechanisms and new pistols had been developed and put into service. The TII was then also replaced by the TIII with improved batteries.

Use edit

There is at least one recorded case of a U-boat being bombed based upon her position being given away by a TI's wake. On 14 September 1939, U-30 was attacked by loitering United Kingdom Fairey Swordfish naval bombers when she fired a TI from her stern torpedo tube at the SS Fanad Head. U-30 was undamaged in the attack and served until she was scuttled at the end of the war.

The TI were also issued in versions with program-steering gyroscopes, using the Fat I and Lut I or Lut II pattern running mechanisms - primary for use in attacking convoys and as self-defence against allied escorts.

Technical data for G7a(TI) torpedo edit

  • Type: Standard, straightrunning torpedo with wet-heater propulsion and whitehead tail
  • Design and development: 1928-33 (based on the 50 cm G7v* torpedo)
  • Operative service in Kriegsmarine: 1934–1945
  • Length, prepared for launch with Ka/Kb warhead and Pi1 pistol): 7163 mm
  • Diameter: 533.4 mm (21")
  • Weight (prepared for launch with warhead): 1538 kg
  • Warhead explosive charge: 250-300 kg of various explosives depending on type of head
  • Boostercharge (Pi1/Pi2 pistols): 300 g Pentrite
  • Minimum angle of impact to detonate (Pi1/Pi2 pistols, mechanical mode): 16 degrees
  • Speed: 30 kn ("Weitschuß", WS) / 40 kn ("Nahschuß", NS) / 44 kn ("Schnellschuß", SS) 1)
  • Depthsetting: 1–12 m (TA-I mechanism) or 1–15 m (TA-II mechanism)
  • Arming distance (Pi1/Pi2 pistols): 100 m (black impeller) / 150 m (red impeller) / 300 m (blue impeller) 2)
  • Propulsion: 4-cylinder steam engine (powered by a mixture of overheated steam and compressed air)
  • Fuel: Decaline
  • Engine power output: 110 Hp (30 kn) / 255 Hp (40 kn) / 350 Hp (44 kn)
  • Engine RPM: 1170 (30 kn) / 1280 (40 kn) / 1470 (44 kn)
  • Propeller: 2 × 6-blade (contra-rotating) 3)
  • Max running distance: 12000 m (30 kn) / 7500 m (40 kn) / 5000 m (44 kn)
  • Air tank capacity: 676 L (200 kg/cm2)
  • Freshwater compartment: 57 L
  • Fueltank: 14.5 L
  • Oiltank (engine): 6.5 L
  • Oiltank (low-pressure regulator): 0.3 L
  • Steering: Mechanical gyroscope powered by pressurised air (GA VIII) with anglesetting mechanism (+/- 90 degrees from initial course after launch)
  • Depthcontrol: Hydrostatic mechanism with pendulum (TA-I or TA-II mechanism)

Note 1) 44kn was used only by S-Boote (problems with initial design led to breakdown on engines running 44 kn, so this setting was banned until the new engine was available). Note 2) Black used only from shore torpedo batteries, red from uboats and blue from surface vessels. Note 3) Pre-war produced models had 4-blade propellers.

Post war use: The TI were used post-war by several navies with different modifications and designations (Marina Española: G-7a, Bundesmarine: DM11, Royal Danish Navy: T1 and T1T, Royal Norwegian Navy: T1 and T1 mod 1). Last known operator was RNoN with the T1 mod 1 (G7a with wire-guidance: Although four modifications to the torpedo were carried out over the years – the last with computerised control in 1992 – the same designation "mod 1" was applied throughout its service). In the RNoN, T1 mod 1 was used from FACs (until ca 1995), submarines (until ca 1990) and Coastal artillery shore batteries (until 2001).

Other versions:

  • G7a(TI Fat I): TI with Fat I programsteering 1)
  • G7a(TI Lut I): TI with Lut I programsteering 1)
  • G7a(TI Lut II): TI with Lut II programsteering 1)
  • G7a(TIü): TI dedicated for use with Schulboote at U-Flotillen. The torpedo was equipped with the older type depth-mechanism, the lead ballast was removed from the water chamber and a special "light" exercise head was fitted (it was empty, i.e. no water and blowing mechanism). This was done to ensure positive buoyancy at the end of the run. Minor adjustments were also done to the air regulators and combustion chamber to lower the temperature of the drive gas (i.e. mixture of steam and pressurized air). These measures lead to a decrease in range, but achieved the overall goal of significantly fewer incidents of damaged or lost torpedoes, and a higher number of exercise-shots for the crews.
  • G7a(TIü Lut II): T1ü with Lut II 2)
  • G7a(TIV): TI with changed buoyancy (max air pressure reduced from 200 to 100 kg/cm2) for the Seehund midget submarine, with sinker-mechanism (never fielded).
  • G7as: TI with acoustic seeker (never fielded, nor designated a KM torpedonumber)

Note 1) For launch with program setting, speed could only be set to 30 kn. Note 2) For launch with program setting, speed could be set to 30 or 40 kn.

Exercise- and Warheads/pistols used on the TI: Exersiceheads:

  • Type 1210 or type 1215 (improved head with dual blow-mechanisms)

Warhead/pistol statutory combinations according to Kriegsmarine regulations:

  • Ka, Ka1 or Ka2 with Pi1, Pi1a or Pi1c pistols
  • Kc with Pi3 or Pi3c pistols
  • Kc1 or Kc2 with Pi3, Pi3a or Pi3c pistols

Warhead/pistol possible (technically) combinations – only on special demand, approved by torpedo-arsenal and with special consideration to depth-settings in order to assure proper function of the pistol:

  • Kb or Kb1 with Pi1, Pi1a, Pi1c, Pi2*, Pi2c* or Pi2c* pistols (* only heads with extended pocket)

See also edit

References edit

Notes edit

  1. ^ Bekker, quoted p.132.

Sources edit

  • Bekker, Cajus. Hitler's Naval War. New York: Zebra Books/Kensington Publishing Corp., 1977. (Reprints 1974 MacDonald and Jane's 1971 translation of Gerhard Stalling Verlag edition)
  • Blair, Clay, Jr. Silent Victory. New York: Bantam, 1976. (Reprints Lippincott 1975 edition)
  • Eberhard Rössler. Die Torpedos der deutschen U-Boote (2.ed), 2005 (ISBN 3-8132-0842-7)
  • Kriegsmarine (T.V.A.): Technische Dienstvorschrift Nr. 194 Torpedo-Kopf-Pistolen-Tabelle, 1944
  • Bundesmarine: Deutsche Unterwasserwaffen - Torpedos, 1967 (German translation of U.S. Navy Ordnance Pamphlet 1673B)
  • Bundesmarine: Torpedo Zünder der Deutschen Marine von 1914 bis 1968 mit historischen Rückblick Band 1, ca 1975
  • Bundesmarine: TDv 1356/004-20 Teil 2 - Bedienungsanweisung einschlisslich Pflege und Sicherheitsmassnahmen für Torpedo DM11 (G7a), 1965
  • Royal Norwegian Navy. SEP-116 Technical manual for Torpedo T1 mod 1, ca 1990 (unofficial - intended as replacement for several regulations like E.12, E.19 etc.)
  • Royal Norwegian Navy. E.12 Manual for torpedo T1 mod 1, ca 1950

External links edit

  • Bismarck class – G7a T1 16 January 2006 at the Wayback Machine
  • uboat.net – The Norwegian Operation and the Torpedo Crisis
  • G7A plans

April 09, 2024
torpedo, standard, issue, kriegsmarine, torpedo, introduced, service, 1934, steam, powered, design, using, heater, engine, burning, decaline, with, range, metres, knots, speed, 1936, kriegsmarine, first, electrical, powered, torpedo, introduced, with, replaced. The G7a TI was the standard issue Kriegsmarine torpedo introduced to service in 1934 It was a steam powered design using a wet heater engine burning decaline with a range of 7 500 metres 24 600 ft at 40 knots 74 km h 46 mph speed In 1936 the Kriegsmarine s first electrical powered torpedo was introduced with the G7e TII It was replaced beginning in 1942 by the G7e TIII The G7a TI remained in service as the main torpedo of Kriegsmarine for the length of the war being the only torpedo used from surface vessels and alongside electric torpedoes on the uboats German G7a TI torpedo at the Norwegian Armed Forces Museum in Oslo Contents 1 Design 2 Use 3 Technical data for G7a TI torpedo 4 See also 5 References 5 1 Notes 5 2 Sources 6 External linksDesign editThe G7a TI torpedo was 533 4 mm 21 00 in in diameter 7 163 millimetres 23 feet 6 0 inches in length with a type Ka or Kb warhead and Pi1 or Pi2 pistol the warhead holding a charge of approximately 280 kg 620 lb of so called Schiesswolle 36 It was Kriegsmarine s first operational torpedo hence TI Torpedo number one and the standard issue torpedo for all German U boats and surface torpedo bearing vessels from 1934 to the end of WW2 nbsp The GA VIII gyroscope as used in the G7a TI torpedoThe torpedo was a straight running unguided design controlled by a gyroscope The TI had variable speed running a distance of 5 000 m at 81 km h 5 500 yd at 44kt 7 500 m at 74 km h 8 250 yd at 40 kt and 12 000 m at 55 6 km h 13 200 yd at 30 kt The 44 kt setting was used only by torpedo boats like the Schnellboote on torpedoes with a reinforced engine The TI was the last naval torpedo of German design in operational use with the traditional standard wet heat method of propulsion The torpedo was powered by an engine fed by a mixture of compressed air and steam Decaline fuel was burning in a combustion chamber creating steam from fresh water The torpedo s speed was determined by the level of pressure three settings for 30 40 44 kn from the low pressure regulator feeding air to the bottom of the combustion chamber The resulting superheated steam powered a four cylinder reciprocating engine in turn powering a pair of contra rotating propellers Though this system of propulsion gave the TI great speed and endurance it had the distinct disadvantage of being very noisy and leaving a long wake of bubbles common to most torpedoes of the period with the exception of the Japanese surface launched Type 93 and submarine launched Type 95 which were fuelled by an enriched oxygen wetheater engine For U boats this relegated the TI for use mainly at night when its wake was least noticeable so as to not give away the element of surprise and the location of the submarine that fired it During daytime the electrical propulsioned torpedoes were favoured For the period 1934 1940 the only available warhead for the TI and TII were the Type Ka with two available pistols The Pi G7A AZ and the Pi G7a MZ The former was a direct acting mechanical pistol while the latter had an additional influence mechanism magnetic Both mechanisms were flawed and contributed to the german Torpedokrise torpedo crisis which lasted from the start of the war and through 1942 The mechanical deflection arms was designed too short and the magnetic igniting mechanism couldn t be properly tuned for the natural magnetic fields in the northern hemisphere and narrow fiords These issues led to premature or late detonations as well as failing to detonate even when hitting the target in numerous cases during this period until properly working pistols were introduced with first the mechanical Pi1 and later the combined mechanical magnetic Pi2 Also the depth mechanism had a design issue leading to leakage of vacuum when stored on the U boats causing the torpedo to run deep The problems were common for the TI and TII torpedoes but the TI also had issues with weak engine blocks cracking at 44 kt setting and the TII had issues with poorly performing batteries The problems were so serious Admiral Donitz said never before in military history has a force been sent into battle with such a useless weapon 1 In general all issues were resolved by 1942 when new depth mechanisms and new pistols had been developed and put into service The TII was then also replaced by the TIII with improved batteries Use editThere is at least one recorded case of a U boat being bombed based upon her position being given away by a TI s wake On 14 September 1939 U 30 was attacked by loitering United Kingdom Fairey Swordfish naval bombers when she fired a TI from her stern torpedo tube at the SS Fanad Head U 30 was undamaged in the attack and served until she was scuttled at the end of the war The TI were also issued in versions with program steering gyroscopes using the Fat I and Lut I or Lut II pattern running mechanisms primary for use in attacking convoys and as self defence against allied escorts Technical data for G7a TI torpedo editType Standard straightrunning torpedo with wet heater propulsion and whitehead tail Design and development 1928 33 based on the 50 cm G7v torpedo Operative service in Kriegsmarine 1934 1945 Length prepared for launch with Ka Kb warhead and Pi1 pistol 7163 mm Diameter 533 4 mm 21 Weight prepared for launch with warhead 1538 kg Warhead explosive charge 250 300 kg of various explosives depending on type of head Boostercharge Pi1 Pi2 pistols 300 g Pentrite Minimum angle of impact to detonate Pi1 Pi2 pistols mechanical mode 16 degrees Speed 30 kn Weitschuss WS 40 kn Nahschuss NS 44 kn Schnellschuss SS 1 Depthsetting 1 12 m TA I mechanism or 1 15 m TA II mechanism Arming distance Pi1 Pi2 pistols 100 m black impeller 150 m red impeller 300 m blue impeller 2 Propulsion 4 cylinder steam engine powered by a mixture of overheated steam and compressed air Fuel Decaline Engine power output 110 Hp 30 kn 255 Hp 40 kn 350 Hp 44 kn Engine RPM 1170 30 kn 1280 40 kn 1470 44 kn Propeller 2 6 blade contra rotating 3 Max running distance 12000 m 30 kn 7500 m 40 kn 5000 m 44 kn Air tank capacity 676 L 200 kg cm2 Freshwater compartment 57 L Fueltank 14 5 L Oiltank engine 6 5 L Oiltank low pressure regulator 0 3 L Steering Mechanical gyroscope powered by pressurised air GA VIII with anglesetting mechanism 90 degrees from initial course after launch Depthcontrol Hydrostatic mechanism with pendulum TA I or TA II mechanism Note 1 44kn was used only by S Boote problems with initial design led to breakdown on engines running 44 kn so this setting was banned until the new engine was available Note 2 Black used only from shore torpedo batteries red from uboats and blue from surface vessels Note 3 Pre war produced models had 4 blade propellers Post war use The TI were used post war by several navies with different modifications and designations Marina Espanola G 7a Bundesmarine DM11 Royal Danish Navy T1 and T1T Royal Norwegian Navy T1 and T1 mod 1 Last known operator was RNoN with the T1 mod 1 G7a with wire guidance Although four modifications to the torpedo were carried out over the years the last with computerised control in 1992 the same designation mod 1 was applied throughout its service In the RNoN T1 mod 1 was used from FACs until ca 1995 submarines until ca 1990 and Coastal artillery shore batteries until 2001 Other versions G7a TI Fat I TI with Fat I programsteering 1 G7a TI Lut I TI with Lut I programsteering 1 G7a TI Lut II TI with Lut II programsteering 1 G7a TIu TI dedicated for use with Schulboote at U Flotillen The torpedo was equipped with the older type depth mechanism the lead ballast was removed from the water chamber and a special light exercise head was fitted it was empty i e no water and blowing mechanism This was done to ensure positive buoyancy at the end of the run Minor adjustments were also done to the air regulators and combustion chamber to lower the temperature of the drive gas i e mixture of steam and pressurized air These measures lead to a decrease in range but achieved the overall goal of significantly fewer incidents of damaged or lost torpedoes and a higher number of exercise shots for the crews G7a TIu Lut II T1u with Lut II 2 G7a TIV TI with changed buoyancy max air pressure reduced from 200 to 100 kg cm2 for the Seehund midget submarine with sinker mechanism never fielded G7as TI with acoustic seeker never fielded nor designated a KM torpedonumber Note 1 For launch with program setting speed could only be set to 30 kn Note 2 For launch with program setting speed could be set to 30 or 40 kn Exercise and Warheads pistols used on the TI Exersiceheads Type 1210 or type 1215 improved head with dual blow mechanisms Warhead pistol statutory combinations according to Kriegsmarine regulations Ka Ka1 or Ka2 with Pi1 Pi1a or Pi1c pistols Kc with Pi3 or Pi3c pistols Kc1 or Kc2 with Pi3 Pi3a or Pi3c pistolsWarhead pistol possible technically combinations only on special demand approved by torpedo arsenal and with special consideration to depth settings in order to assure proper function of the pistol Kb or Kb1 with Pi1 Pi1a Pi1c Pi2 Pi2c or Pi2c pistols only heads with extended pocket See also editG7e torpedo List of World War II torpedoes of GermanyReferences editNotes edit Bekker quoted p 132 Sources edit Bekker Cajus Hitler s Naval War New York Zebra Books Kensington Publishing Corp 1977 Reprints 1974 MacDonald and Jane s 1971 translation of Gerhard Stalling Verlag edition Blair Clay Jr Silent Victory New York Bantam 1976 Reprints Lippincott 1975 edition Eberhard Rossler Die Torpedos der deutschen U Boote 2 ed 2005 ISBN 3 8132 0842 7 Kriegsmarine T V A Technische Dienstvorschrift Nr 194 Torpedo Kopf Pistolen Tabelle 1944 Bundesmarine Deutsche Unterwasserwaffen Torpedos 1967 German translation of U S Navy Ordnance Pamphlet 1673B Bundesmarine Torpedo Zunder der Deutschen Marine von 1914 bis 1968 mit historischen Ruckblick Band 1 ca 1975 Bundesmarine TDv 1356 004 20 Teil 2 Bedienungsanweisung einschlisslich Pflege und Sicherheitsmassnahmen fur Torpedo DM11 G7a 1965 Royal Norwegian Navy SEP 116 Technical manual for Torpedo T1 mod 1 ca 1990 unofficial intended as replacement for several regulations like E 12 E 19 etc Royal Norwegian Navy E 12 Manual for torpedo T1 mod 1 ca 1950External links editBismarck class G7a T1 Archived 16 January 2006 at the Wayback Machine uboat net The Norwegian Operation and the Torpedo Crisis G7A plans Retrieved from https en wikipedia org w index php title G7a torpedo amp oldid 1210834695, wikipedia, wiki, book, books, library,

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