Wind turbine unlocking

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A ready-to-drop bomb with windmill release and safety wire on the head detonator in the weapon bay of an aircraft
Bomb with windmill release on the head and tail fuse and safety wire
Detonator with rotating cap

The wind turbine or propeller unlocking (also wind turbine or propeller locking ) is a type of unlocking or sharpening of a detonator for bombs or rockets .

When aerial bombs were first used on a larger scale during the First World War, safe detonators were sought especially in Germany and England . The detonators should be safe during transport and also in an emergency landing , but on the other hand trigger reliably after being dropped over the target. When bombs are dropped in groups, they often crash in midair shortly after being dropped. The detonators must not trigger these collisions either, as an explosion so close to the aircraft would destroy it. Similar requirements for safe fuses existed before with artillery shells ; Due to the strong acceleration when firing there, it is easier to unlock the fuse without external technical means. Such high forces do not work when a bomb is dropped, so you had to go other ways. Therefore, detonators with wind turbine release were developed soon after the war began.

The wind turbine is usually designed as a propeller or sometimes as an impeller . With head detonators, the wind turbine is located directly on the detonator. Instead of a separate wind turbine, there are also designs in which the cap of the detonator is equipped with aerodynamic blades that set the cap in rotation. In the case of rear fuses, on the other hand, the wind turbine is often not directly on the fuse; the slipstream of the bomb body prevents a reliable air flow through the wind turbine. Then the wind turbine is attached to a shaft that acts as an extension to the igniter.

Before the bomb is dropped, a safety wire attached to the aircraft locks the wind turbine and prevents it from rotating too early. When the bomb is dropped, the safety wire is pulled out of the wind turbine lock and the wind turbine begins to turn. The wind turbine rotates in the air flow and thus moves a mechanism that unlocks the fuse after a number of rotations. In the event of an attack at low altitude , it can therefore happen that the fuse is not yet unlocked.

The windmill release is used for many fuzes , such as impact fuses , time fuses or proximity fuses . Due to the use in different types of detonators, as well as the place of use as head or rear detonators, there are different technical constructions. Usually the wind turbine is attached to a bolt . The bolt is screwed into the detonator body with a thread and initially locks the trigger mechanism. Through several revolutions of the windmill, the bolt until the stopper is unscrewed and thus unlocks the trigger mechanism.

Individual evidence

  1. ↑ Wolfgang Fleischer: German dropping ammunition until 1945 p. 22, 194
  2. ↑ a b L.Dv. 152/28 Draft of a fuse regulation - Part 2: Technical principles of the mechanical fuse for dropping ammunition 1938, Chapter II.1.d [1]
  3. ↑ Fritz Hohm: The weapons of the air forces , 1935 pp. 152, 155 [2]
  4. ↑ a b c United States Navy Bomb Disposal: BRITISH ROCKTES AND FUZES , July 1945, SECTION VI - ROCKET FUZES [3]
  5. ↑ a b Wolfgang Fleischer: German drop ammunition until 1945 pp. 19–20
  6. ↑ Bruce Gordon: The Spirit of Attack , Verlag Author House, 2014, ISBN 9781491846032 p. 65 [4]
  7. ^ A b c Mike Pickett: Explosives Identification Guide , Verlag Cengage Learning, 2004, ISBN 9781401878214 p. 9 [5]
  8. ↑ Pilot's Information File , 1943, United States Army Air Forces p. 212 [6]
  9. ↑ Thomas Gersbeck: Practical Military Ordnance Identification , Verlag CRC Press , 2014, ISBN 9781439850589 , pp. 40, 49, 57 [7]