HACS
High Angle Control System (HACS) was a British
Early history
The HACS was first proposed in the 1920s and began to appear on
Development
Operation
The bearing and altitude of the target was measured directly on the UD4 Height Finder/Range Finder, a
This calculated range rate was fed back to the UD4 where it powered a motor to move prisms within the UD4. If all the measurements were correct, this movement would track the target, making it appear motionless in the sights.
The angle measured by the graticule also caused a metal wire to rotate around the face of a large circular display on one side of the HACS, known as the Deflection Display. The measured value of altitude and range, and estimated value of target speed, caused optics to focus a lamp onto a ground glass screen behind the wire, displaying an ellipse whose shape changed based on these measures. The deflection operator used two controls to move additional wire indicators so they lay on top of the intersection of the outer edge of the ellipse where it was crossed by the rotating metal wire.[13] The intersection of the ellipse and the target direction was used as a basis for calculating elevation and training of the guns. The ellipse method had the advantage of requiring very little in the way of mechanical computation and essentially modelled target position in real-time with a consequent rapid solution time.[14]
Information flow
The HADT provides target direction, range, speed, altitude and bearing data to the HACP, which transmits direction and fuse timing orders to the guns. The HACP transmits the computer generated range rate and generated bearing back to the HADT, creating a feedback loop between the HADT and HACP, so that the fire control solution generated by the computer becomes more accurate over time if the target maintains a straight line course. The HADT also observes the accuracy of the resulting shell bursts and uses these bursts to correct target speed and direction estimates, creating another feed back loop from the guns to the HADT and thence to the HACP, again increasing the accuracy of the solution, if the target maintains a straight line course.[15] Most guns controlled by the HACS had Fuze Setting Pedestals or Fuze Setting Trays where the correct fuze timing was set on a clockwork mechanism within the AA shell warhead, so that the shell would explode in the vicinity of the target aircraft.
Target drones
The HACS was the first Naval AA system to be used against
Tachometric and radar additions
The RN moved quickly to add true tachometric target motion prediction and radar ranging to the HACS by mid 1941. The RN was the first navy to adopt dedicated FC AA radars. However the system, in common with all World War II-era mechanical AA fire control system still had severe limitations as even the highly advanced
The Fuze Keeping Clock
RN destroyers were hampered by the lack of good dual-purpose weapons suitable for ships of destroyer size; for much of the war 40° was the maximum elevation of the 4.7-inch (119 mm) guns equipping such ships, which were consequently unable to engage directly attacking dive bombers, although they could provide "barrage" and "predicted fire" to protect other ships from such attacks.[28] Destroyers did not use HACS, but rather the Fuze Keeping Clock (FKC), a simplified version of HACS.[29] Starting in 1938 all new RN destroyers, from the Tribal class onwards, were fitted with a FKC and continuous prediction fuse setting trays for each main armament gun.[30] WWII experience from all navies showed that dive bombers could not be engaged successfully by any remote computer-predictive AA system using mechanical fuzes[31][32] due to the lag time in the computer and the minimum range of optical rangefinders.[33] In common with other contemporary navies, pre-war designed RN destroyers suffered from a lack of short-range, rapid-fire AA with which to engage dive bombers.
The Auto Barrage Unit
The Auto Barrage Unit or ABU, was a specialized gunnery computer and radar ranging system that used Type 283 radar. It was developed to provide computer prediction and radar anti-aircraft fire control to main and secondary armament guns that did not have inherent anti-aircraft capability. The ABU was designed to allow the guns to be pre-loaded with time fused ammunition, and it then tracked incoming enemy aircraft, aimed the guns continuously to track the aircraft, and then fired the guns automatically when the predicted aircraft position reached the preset fuse range of the previously loaded shells.[34] The ABU was also used with guns that were nominally controlled by the HACS to provide a limited blind fire capability.[35][36]
Wartime experience
By May 1941, RN cruisers, such as HMS Fiji, were engaging the Luftwaffe with stabilized HACS IV systems with GRU/GRUB and Type 279 radar with the Precision Ranging Panel, which gave +/- 25 yd accuracy out to 14,000 yds. HMS Fiji was sunk in the Battle of Crete after running out of AA ammunition but her HACS IV directed 4-inch AA gun battery fended off Luftwaffe attacks for many hours.[37]
Demonstrating the RN's rapid strides in naval AA gunnery, in May 1941,
The RN made the following claims for ship borne anti-aircraft fire against enemy aircraft, from September 1939 up to 28 March 1941: :Certain kills: 234, Probable kills: 116, Damage claims: 134[41]
The RN made the following claims for ship borne anti-aircraft fire against enemy aircraft, from September 1939 up to 31 Dec 1942:[42]
- Major warships (ships likely to have HACS or FKC fire control systems)
- Certain kills: 524
- Probable kills: 183
- Damage claims: 271
- Minor warships and merchant vessels (most having no AA fire control systems)
- Certain kills: 216
- Probable kills: 83
- Damage claims: 177
- Total kill claims: 740
- Total probable claims: 266
- Total damage claims: 448
Radar and the Mark VI Director
HACS used various director towers that were generally equipped with Type 285 as it became available. This metric wavelength system employed six
HACS systems in use or planned in August 1940
HACS Directors fitted to ships in a document dated as "revised Aug 1940":[44]
- HACS III: ABC transmission, AV cradle for 15 ft HF/RF. Introduced Mk III table.
- HMS Ajax, Galatea, Arethusa, Coventry, HMAS Hobart, Sydney, Perth
- HACS III*: Similar to MarkIII but with larger windscreen and space for a rate officer.
- HMS Penelope, Southampton, Newcastle, Malaya, Hood*, Australia*, Nelson*, Royal Sovereign*, Barham*, Resolution*, Cairo*, Excellent (gunnery training school)*, Revenge*, Calcutta*, Carlisle*, Curacoa*, Exeter*, Adventure*, Warspite*. Ships marked with * had roll stabilization for layer.
- HACS III*G as mark III but fitted with GRU and roll stabilization for the layer.
- HACS IV: Similar to MkIII but with circular screen, magslip transmission and roll stabilization for the layer. Introduced Mk IV table.
- HMS Birmingham, Sheffield, Glasgow, Aurora, Liverpool, Manchester, Gloucester, Dido, and Fiji classes, Forth, Maidstone, Renown, Valiant, Illustrious, Formidable and Ark Royal.
- HACS IV G: Mk IV with Gyro rate unit.
- Dido class and Fiji classes.
- HACS IV GB: Mk IV and fitted with GRU and complete stabilization in laying and training, Keelavite system of power training.
- HMS King George V and Prince of Wales, Dido and Fiji classes.
- HACS V: Improved design, partially enclosed, complete stabilization for elevation and training. Keelavite system of power training, and GRU. Duplex 15 ft HF/RF. Uses Mk IV table.
- HMS Duke of York, Anson and Howe.
- HACS V* :As Mk V but single HF/RF and raised HF/RF compared to Mk V.[45]
- HMS Indomitable, Implacable and Indefatigable.
See also
References
- ^ Weapon Control in the Royal Navy 1935-45, Pout, from The Application of Radar and other Electronic Systems in the Royal Navy in WW2, p87 (Kingsley-editor)
- ^ Appendix one, Classification of Director Instruments, see external links.
- ^ Weapon Control in the Royal Navy 1935-45, Pout, from The Application of Radar and other Electronic Systems in the Royal Navy in WW2, p87,99 (ed Kingsley)
- ^ HACS III Operating Manual Part 1, paragraph 2 (a-o)
- ^ British Mechanical Gunnery Computers of World War II, Bromley, p19
- ^ The Gunnery Pocket Book, B.R. 224/45, 1945, paragraphs 429-431. See external links
- ^ HACS III Operating Manual Part 2, paragraph 300,301
- ^ HACS III Operating Manual Part 1, paragraph 2 (a)
- ^ Weapon Control in the Royal Navy 1935-45, Pout
- ^ British Mechanical Gunnery Computers of World War II, Bromley, p22
- ^ Naval Weapons of World War Two, Campbell, p. 30
- ^ HACS III Operating Manual Part 2, paragraph 174 (a)
- ^ The Gunnery Pocket Book, B.R. 224/45, 1945, paragraphs 424. See external links.
- ^ British Mechanical Gunnery Computers of World War II, Bromley, p19, figure 18
- ^ British Mechanical Gunnery Computers of World War II, Bromley
- ^ Unmanned Aviation, Newcombe, p47
- ^ The British Defense of Egypt, 1935-40, Morewood.P70-71
- ^ UK Hansard, Queen Bee Aircraft (shooting practice). HC Debate07 June 1939 volume 348 column 427W:
- ^ The Naval Review, A Misleading Success, July 1978, Jones, Basil, p254:
- ^ HACS Target practice video
- ^ ADM 186/339: Progress in naval gunnery, 1914-1936, p132. See external links
- ^ Naval Weapons of WW2, Campbell, P106. This data in turn was based upon USN wartime AA kill claims, and so probably overstates the system's effectiveness.
- ^ HACS III Operating Manual Part 1, paragraph 56,61
- ^ Weapon Control in the Royal Navy 1935-45, Pout, p104, from The Application of Radar and other Electronic Systems in the Royal Navy in WW2 (Kingsley-editor)
- ^ British Battleships of World War Two, Raven & Roberts, p378:
- ^ Weapon Control in the Royal Navy 1935-45, Pout, p97
- ^ Naval Weapons of WW2, Campbell, pp. 17–18
- ^ Tribal Class Destroyers, Hodges, p27
- ^ Naval Weapons of WW2, Campbell, p19
- ^ Tribal Class Destroyers, Hodges, p27
- ^ Summary of USN and RN gunnery reports. For example, the USS Enterprise reported her Mk 33 AAFC system as "ineffective" against dive bombers. USS ENTERPRISE CV6/A16-3/(10-My)
- ^ US Destroyers-An Illustrated Design History, Friedman, p203:
- ^ HACS III Operating Manual Part 2
- ^ The Gunnery Pocket Book, paragraph 448
- ^ Campbell, Naval Weapons of World War Two, p16.
- ^ Victor Humphries, HMS Renown WWII: "I was a radar RP3 rating on board HMS Renown during WW2. During which time I operated the ABU, which was very reliable; the set itself was not very big, the CRT being about 9 inches in diameter. The screen showed two green lines, the top one straight across the screen and the lower line had about a 1/4-inch step which was moved across the screen with a steering wheel situated below and to the left, which had a smaller steering wheel attached to it so that on moving the larger steering wheel to keep the step steady on the left side of the echo. Once I was satisfied that the aircraft was moving in at a steady speed, I could LOCK on with the small steering wheel and the stepped line would close in with the echo. There was an indicator on the screen at 5000 yards; when the aircraft was inside this range I could see by a green light that all guns were loaded, cocked, and ready to fire; all I then had to do was depress a foot pedal which fired ten 4.5-inch guns, either on the port or starboard sides. If the aircraft echo produced a downward echo every so many seconds (the number of seconds decided just before the operation) it would indicate IFF = identification friend or foe, which meant it was our own aircraft, if there was no IFF and the pilot did not break radio silence he could be shoot down. We also had long range aircraft warning Radar Type 281, which would warn of approaching enemy aircraft 150 miles away, and at WW2 aircraft speeds we had time to prepare. The types 273 & 284 are another story."
- ^ The true experiences of Mr Leonard Charles Eades during the Second World War, from the HMS Fiji Association.
- ^ The Development of Radar Equipments for the Royal Navy, Kingsley, p383.
- ^ The Royal Navy and the Mediterranean Convoys. A Naval Staff History, p26
- ^ Battleship: The Loss of the Prince of Wales and the Repulse, Middlebrook
- ^ March, British Destroyers, p. 434.
- ^ United States Navy, AntiAircraft Action Summary, July 1942 to Dec 1942 (Information Bulletin No. 22), pp. 281–282.
- ^ Weapon Control in the Royal Navy 1935-45, Pout, pp. 105-106.
- ^ Appendix one, Classification of Director Instruments.
- ^ Uses FKC AAFC table according to Campbell.
External links
- Newsreel video of HACS controlled guns in action Archived 11 June 2011 at the Wayback Machine
- More Newsreel footage of HACS guns engaging high level bombers Archived 5 June 2011 at the Wayback Machine
- HACS: A Debacle or Just-in-Time?)
- Illustration of the HACS Deflection Screen
- Appendix one, Classification of Director Instruments
- HACS III Operating manual Part 1
- HACS III Operating manual Part 2
- USS Enterprise Action Log
- The Gunnery Pocket Book, B.R. 224/45, 1945
- The true experiences of Mr. Leonard Charles
- HACS III*G with Type 285 Radar and the MkIII table
- British Mechanical Gunnery Computers of World War II
- Progress in Naval Gunnery, 1914–1936
- Memoirs of Sub-Lieutenant Robert Hughes, Gunnery Control Officer on HMS Scylla