Fuze Keeping Clock

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Device used for a fire control computer

title: "Fuze Keeping Clock" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["anti-aircraft-artillery", "military-computers", "naval-artillery", "artillery-operation", "equipment-of-the-royal-navy", "fire-control-computers-of-world-war-ii", "military-equipment-introduced-in-the-1930s"] description: "Device used for a fire control computer" topic_path: "history" source: "https://en.wikipedia.org/wiki/Fuze_Keeping_Clock" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Device used for a fire control computer ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/b/b0/HMS_Belfast_-4_inch_guns-_shell_loading_1.jpg" caption="A Mk V Fuze setting tray with a 4 in (102 mm) anti-aircraft (A/A) round. The Fuze setting tray received its fuze timing information, via electrical signals from the FKC, on a receiver dial. The operator then matched the settings on the receiver dial with the indicator dial on the tray, which then adjusted the clockwork mechanism in the A/A warhead to the calculated time of flight to the target."] ::

The Fuze Keeping Clock (FKC) was a simplified version of the Royal Navy's High Angle Control System analogue fire control computer. It first appeared as the FKC MkII in destroyers of the 1938 , while later variants were used on sloops, frigates, destroyers, aircraft carriers and several cruisers. The FKC MkII was a non-tachymetric anti-aircraft fire control computer. It could accurately engage targets with a maximum speed of 250 kn.

Operation

The FKC received vertical reference information from a Gyro Level Corrector and aircraft altitude, range, direction, and speed input information from the Rangefinder-Director, and output to the guns the elevation and deflection data needed to hit the target, along with the correct fuze timing information, so that the shells fired would explode in the vicinity of the target aircraft. Most guns controlled by the FKC had Fuze Setting Pedestals or Fuze Setting Trays where the correct fuze timing was set on a clockwork mechanism within the AA shell warhead.

::figure[src="https://upload.wikimedia.org/wikipedia/commons/a/a5/Radar_and_Electronic_Warfare_1939-1945_A28824.jpg" caption="Cut-away view of a destroyer "K" type D.C.T. with Type 285 radar. The below-decks FKC is shown in the centre of the drawing and is labelled "Gunnery Calculating Position", with the deflection operator seated."] ::

Development

Type 285 radar was an early addition to the FKC system, being fitted on new destroyers from mid-1941 onward, and retrofitted to existing destroyers as time and opportunity permitted. Later variants increased the maximum target speed to 500 kn, and were combined with Gyro Rate Units (GRU) which gave tachometric capabilities to the system, and radar which greatly improved ranging and rate keeping accuracy.

Wartime use

::figure[src="https://upload.wikimedia.org/wikipedia/commons/d/d0/HMS_Auckland_(L61)_IWM_FL_1201.jpg" caption="Port view of the sloop HMS ''Auckland''. She is armed with eight 4-inch Mark XVI guns in four twin Mark XIX mountings at A and B positions forward and in X and Y positions aft. They are controlled by the Rangefinder-Director sited behind the bridge which fed targeting information to her FKC located below decks. A [[Vickers .50 machine gun]], quad mount Mk. II, was also fitted."] ::

The FKC saw extensive use during the war on British Commonwealth naval ships, typically on destroyers and sloops. Prior to the widespread use of radar, optical detection and ranging on high altitude aerial targets was a daunting task, as shown by 's Report of Proceedings, for 3 September 1940:

Occasionally conditions would conspire to favour the surface ships during an aerial attack, as again revealed by HMAS Parramattas Report of Proceedings, for 20 September 1940:

The FKC was used throughout the war and its effectiveness was increased by the use of radar for gunnery and to provide warning against surprise attack, as demonstrated by this account of bringing down a Japanese A6M Zero fighter aircraft (a "HAMP"), in 1944: The "HAMP" was seen to crash approximately one mile west of Dodola Island. This was confirmed later by an American Army Officer serving on Dodola Island and also by a tidal observation party from "WARREGO", camped on Kokova Island.}}

Notes

References

  1. ''The Gunnery Pocket Book'', pp. 153–54, paragraphs 432–35
  2. ''Tribal Class Destroyers'', Hodges, p. 27
  3. Naval Weapons of WW2, Campbell, p. 19
  4. Hodges and Friedman, ''Destroyer weapons of WW2'', p. 51
  5. Hodges and Friedman, ''Destroyer weapons of WW2'', p. 95–96
  6. Howse, ''Radar at sea: The Royal Navy in World War 2''
  7. Destroyer Weapons of WW2, Hodges/Friedman, p. 102
  8. Naval Weapons of WW2, Campbell
  9. [https://www.awm.gov.au/collection/C1421662 HMAS Parramatta Report of Proceedings, AWM78, Folder 290/1 – May 1940 - December 1945 ], p. 125
  10. HMAS Parramatta Report of Proceedings, AWM78, Folder 290/1 – May 1940 - December 1945, p. 126
  11. The FKC Mk II could set target speed to a maximum of 250 knots or 288 mph.
  12. [http://www.navy.gov.au/sites/default/files/documents/Naval%20Warfare%20Nov-1944.pdf ACB 0254/45(4) ''Royal Australian Navy Monthly Naval Warfare Review (WWII)''] November 1944, pp. 3–4

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anti-aircraft-artillerymilitary-computersnaval-artilleryartillery-operationequipment-of-the-royal-navyfire-control-computers-of-world-war-iimilitary-equipment-introduced-in-the-1930s