page_title: Fire-control system
section_title: World War II
hierarchical_section_title: Fire-control system / Naval based fire control / World War II
caption_attribution_description: English: Radar and Electronic Warfare 1939-1945 Naval Radar: Diagram to illustrate the chain of command in High Angle Fire Control. Signals are picked up by the aerial array. The Radar operator (bottom) sees the 'echo' and transmits its range to the gunnery calculating position. The Layer and Trainer in the gun director transmit to the gunnery calculating position the bearing of the target. If the target cannot be seen the Radar display panel (left) is used to provide a radar bearing and the guns are thus able to fire 'blind'. The remainder of the crew are members of the gunnery team.
context_page_description: A fire-control system is a number of components working together, usually a gun data computer, a director, and radar, which is designed to assist a ranged weapon system in targeting, tracking and hitting its target. It performs the same task as a human gunner firing a weapon, but attempts to do so faster and more accurately.
context_section_description: During their long service life, rangekeepers were updated often as technology advanced, and by World War II they were a critical part of an integrated fire control system. The incorporation of radar into the fire control system early in World War II provided ships the ability to conduct effective gunfire operations at long range in poor weather and at night. For U.S. Navy gun fire control systems, see ship gun fire-control systems.
  The use of director-controlled firing, together with the fire control computer, removed the control of the gun laying from the individual turrets to a central position; although individual gun mounts and multi-gun turrets would retain a local control option for use when battle damage limited director information transfer (these would be simpler versions called "turret tables" in the Royal Navy). Guns could then be fired in planned salvos, with each gun giving a slightly different trajectory. Dispersion of shot caused by differences in individual guns, individual projectiles, powder ignition sequences, and transient distortion of ship structure was undesirably large at typical naval engagement ranges. Directors high on the superstructure had a better view of the enemy than a turret mounted sight, and the crew operating them were distant from the sound and shock of the guns. Gun directors were topmost, and the ends of their optical rangefinders protruded from their sides, giving them a distinctive appearance.
  Unmeasured and uncontrollable ballistic factors, like high altitude temperature, humidity, barometric pressure, wind direction and velocity, required final adjustment through observation of the fall of shot. Visual range measurement (of both target and shell splashes) was difficult prior to availability of Radar. The British favoured coincident rangefinders while the Germans favored the stereoscopic type. The former were less able to range on an indistinct target but easier on the operator over a long period of use, the latter the reverse.
  Submarines were also equipped with fire control computers for the same reasons, but their problem was even more pronounced; in a typical "shot", the torpedo would take one to two minutes to reach its target. Calculating the proper "lead" given the relative motion of the two vessels was very difficult, and torpedo data computers were added to dramatically improve the speed of these calculations.
  In a typical World War II British ship the fire control system connected the individual gun turrets to the director tower (where the sighting instruments were located) and the analogue computer in the heart of the ship. In the director tower, operators trained their telescopes on the target; one telescope measured elevation and the other bearing. Rangefinder telescopes on a separate mounting measured the distance to the target. These measurements were converted by the Fire Control Table into the bearings and elevations for the guns to fire upon. In the turrets, the gunlayers adjusted the elevation of their guns to match an indicator for the elevation transmitted from the Fire Control table—a turret layer did the same for bearing. When the guns were on target they were centrally fired.
  Even with as much mechanization of the process, it still required a large human element; the Transmitting Station (the room that housed the Dreyer table) for HMS Hood's main guns housed 27 crew.
  Directors were largely unprotected from enemy fire. It was difficult to put much weight of armour so high up on the ship, and even if the armour did stop a shot, the impact alone would likely knock the instruments out of alignment. Sufficient armour to protect from smaller shells and fragments from hits to other parts of the ship was the limit.
  The performance of the analog computer was impressive. The battleship USS North Carolina during a 1945 test was able to maintain an accurate firing solution on a target during a series of high-speed turns.
   It is a major advantage for a warship to be able to maneuver while engaging a target.
  Night naval engagements at long range became feasible when rad
caption: Accurate fire control systems were introduced in the early 20th century. Pictured, a cut-away view of a destroyer. The below deck analog computer is shown in the centre of the drawing and is labelled "Gunnery Calculating Position".
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