A director, also called an auxiliary predictor, [1] is a mechanical or electronic computer that continuously calculates trigonometric firing solutions for use against a moving target, and transmits targeting data to direct the weapon firing crew.
A director, also called an auxiliary predictor, [1] is a mechanical or electronic computer that continuously calculates trigonometric firing solutions for use against a moving target, and transmits targeting data to direct the weapon firing crew.
For warships of the 20th century, the director is part of the fire control system; it passes information to the computer that calculates range and elevation for the guns. Typically, positions on the ship measured range and bearing of the target; these instantaneous measurements are used to calculate rate of change values, and the computer ("fire control table" in Royal Navy terms) then predicts the correct firing solution, taking into account other parameters, such as wind direction, air temperature, and ballistic factors for the guns. The British Royal Navy widely deployed the Pollen and Dreyer Fire Control Tables during the First World War, while in World War II a widely used computer in the US Navy was the electro-mechanical Mark I Fire Control Computer.
On ships the director control towers for the main battery are placed high on the superstructure, where they have the best view. Due to their large size and weight, in the World War II era the computers were located in plotting rooms deep in the ship, below the armored deck on armored ships.
Directors were introduced into field artillery in the early 20th century to orient the guns of an artillery battery in their zero line (or 'centre of arc'). Directors were an essential element in the introduction of indirect artillery fire. In US service these directors were called 'aiming circles'. Directors could also be used instead of theodolites for artillery survey over shorter distances. The first directors used an open sight rotating on an angular scale (e.g. degrees & minutes, grads or mils of one sort or another), but by World War I most directors were optical instruments. Introduction of digital artillery sights in the 1990s removed the need for directors.
Directors were mounted on a field tripod and oriented in relation to grid north of the map. If time was short this orientation usually used an integral compass, but was updated by calculation (azimuth by hour angle or azimuth by Polaris) or 'carried' by survey techniques from a survey control point. In the 1960s gyroscopic orientation was introduced.
For anti-aircraft use, directors are usually used in conjunction with other fire control equipment, such as height finders or fire control radars. [2] In some armies these 'directors' were called 'predictors'. The Mark 51 director was used by the US Navy for 40 mm guns and later for 3"/50 caliber guns. [3] The Kerrison Predictor was also designed to be used with the Bofors 40 mm gun.
The Bofors 40 mm gun (called a fire unit) used in its anti-aircraft role has the M5 director for its fire-control system. [4] The director is operated by a member of the range section who reports to the chief of section, who in turn reports to the platoon commander. The range section's leader is also called a range setter; he guides the preparation of the director and generator for firing, verifies the orientation and synchronisation of the gun and the director, and supervises fire control using the M5 director (or by the carriage when the M7 Weissight is used). The range section that uses the M5 director consists of the range setter, elevation tracker, azimuth tracker, power plant operator and telephone operator.
The M5 director is used to determine or estimate the altitude or slant range of the aerial target. Two observers then track the aircraft through a pair of telescopes on opposite sides of the director. The trackers turn handwheels to keep the crosshairs of their respective telescope on the aircraft image. The rotation of the handwheels provides the director with data on the aircraft's change in elevation and change in azimuth in relation to the director. As the mechanisms inside the director respond to the rotation of the handwheels, a firing solution is mechanically calculated and continuously updated for as long as the target is tracked. Essentially, the director predicts future position based on the aircraft's present location and how it is moving.
After their introduction, directors soon incorporated correction factors that could compensate for ballistic conditions such as air density, wind velocity and wind direction. If the director was not located near the gun sections, a correction for parallax error could also be entered to produce even more accurate firing direction calculations. [5]
Directors transmit three important calculated firing solutions to the anti-aircraft gun firing crew: the correct firing azimuth and quadrant elevation calculated to determine where exactly to aim the gun, and for guns that use ammunition with timed fuzes, the director also provides the flight time for the projectile so the fuze can be set to detonate close to the target.
Early anti-aircraft artillery batteries located the directors in the middle of the position, with the firing sections (guns) located at the corners of the position. [6] Before the introduction of radars, searchlights were used in conjunction with directors to allow night target engagement. [7]
Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action". It includes surface based, subsurface, and air-based weapon systems, associated sensor systems, command and control arrangements, and passive measures. It may be used to protect naval, ground, and air forces in any location. However, for most countries, the main effort has tended to be homeland defence. NATO refers to airborne air defence as counter-air and naval air defence as anti-aircraft warfare. Missile defence is an extension of air defence, as are initiatives to adapt air defence to the task of intercepting any projectile in flight.
Indirect fire is aiming and firing a projectile without relying on a direct line of sight between the gun and its target, as in the case of direct fire. Aiming is performed by calculating azimuth and inclination, and may include correcting aim by observing the fall of shot and calculating new angles.
The Kerrison Predictor was one of the first fully automated anti-aircraft fire-control systems. It was used to automate the aiming of the British Army's Bofors 40 mm guns and provide accurate lead calculations through simple inputs on three main handwheels.
The Bofors 40 mm Automatic Gun L/60 is an anti-aircraft autocannon, designed in the 1930s by the Swedish arms manufacturer AB Bofors. The gun was designed as an intermediate anti-aircraft gun, filling the gap between fast firing close-range small calibre anti-aircraft guns and slower firing long-range high calibre anti-aircraft guns, a role which previously was filled by older outdated guns. The Bofors 40 mm L/60 was for its time perfectly suited for this role and outperformed competing designs in the years leading up to World War II in both effectiveness and reliability.
A fire-control system (FCS) 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 to target, track, and hit a target. It performs the same task as a human gunner firing a weapon, but attempts to do so faster and more accurately.
Gun laying is the process of aiming an artillery piece or turret, such as a gun, howitzer, or mortar, on land, in air, or at sea, against surface or aerial targets. It may be laying for direct fire, where the gun is aimed similarly to a rifle, or indirect fire, where firing data is calculated and applied to the sights. The term includes automated aiming using, for example, radar-derived target data and computer-controlled guns.
The SCR-268 was the United States Army's first radar system. Introduced in 1940, it was developed to provide accurate aiming information for antiaircraft artillery and was also used for gun laying systems and directing searchlights against aircraft. The radar was widely utilized by both Army and Marine Corps air defense and early warning units during World War II. By the end of World War II the system was already considered out of date, having been replaced by the much smaller and more accurate SCR-584 microwave-based system.
The Flak 30 and improved Flak 38 were 20 mm anti-aircraft guns used by various German forces throughout World War II. It was not only the primary German light anti-aircraft gun but by far the most numerously produced German artillery piece throughout the war. It was produced in a variety of models, notably the Flakvierling 38 which combined four Flak 38 autocannons onto a single carriage.
High Angle Control System (HACS) was a British anti-aircraft fire-control system employed by the Royal Navy from 1931 and used widely during World War II. HACS calculated the necessary deflection required to place an explosive shell in the location of a target flying at a known height, bearing and speed.
Rangekeepers were electromechanical fire control computers used primarily during the early part of the 20th century. They were sophisticated analog computers whose development reached its zenith following World War II, specifically the Computer Mk 47 in the Mk 68 Gun Fire Control system. During World War II, rangekeepers directed gunfire on land, sea, and in the air. While rangekeepers were widely deployed, the most sophisticated rangekeepers were mounted on warships to direct the fire of long-range guns.
The gun data computer was a series of artillery computers used by the U.S. Army for coastal artillery, field artillery and anti-aircraft artillery applications. For antiaircraft applications they were used in conjunction with a director computer.
The Iowa-class battleships are the most heavily armed gunships the United States Navy has ever put to sea, due to the continual development of their onboard weaponry. The first Iowa-class ship was laid down in June 1940; in their World War II configuration, each of the Iowa-class battleships had a main battery of 16-inch (406 mm) guns that could hit targets nearly 20 statute miles (32 km) away with a variety of artillery shells designed for anti-ship or bombardment work. The secondary battery of 5-inch (127 mm) guns could hit targets nearly 9 statute miles (14 km) away with solid projectiles or proximity fuzed shells, and was effective in an anti-aircraft role as well. Each of the four battleships carried a wide array of 20 mm and 40 mm anti-aircraft guns for defense against enemy aircraft.
A fire control tower is a structure located near the coastline, used to detect and locate enemy vessels offshore, direct fire upon them from coastal batteries, or adjust the aim of guns by spotting shell splashes. Fire control towers came into general use in coastal defence systems in the late 19th century, as rapid development significantly increased the range of both naval guns and coastal artillery. This made fire control more complex. These towers were used in a number of countries' coastal defence systems through 1945, much later in a few cases such as Sweden. The Atlantic Wall in German-occupied Europe during World War II included fire control towers.
The 37 mm gun M1 was an anti-aircraft autocannon developed in the United States. It was used by the US Army in World War II.
The QF 3-inch 20 cwt anti-aircraft gun became the standard anti-aircraft gun used in the home defence of the United Kingdom against German Zeppelins airships and bombers and on the Western Front in World War I. It was also common on British warships in World War I and submarines in World War II. 20 cwt referred to the weight of the barrel and breech, to differentiate it from other 3-inch guns. While other AA guns also had a bore of 3 inches (76 mm), the term 3-inch was only ever used to identify this gun in the World War I era, and hence this is what writers are usually referring to by 3-inch AA gun.
The QF 1 pounder, universally known as the pom-pom due to the sound of its discharge, was a 37 mm British autocannon, the first of its type in the world. It was used by several countries initially as an infantry gun and later as a light anti-aircraft gun.
The QF 5.25-inch Mark I gun was the heaviest dual-purpose gun used by the Royal Navy during the Second World War. Although considered less than completely successful, it saw extensive service. 267 guns were built.
Ship gun fire-control systems (GFCS) are analogue fire-control systems that were used aboard naval warships prior to modern electronic computerized systems, to control targeting of guns against surface ships, aircraft, and shore targets, with either optical or radar sighting. Most US ships that are destroyers or larger employed gun fire-control systems for 5-inch (127 mm) and larger guns, up to battleships, such as Iowa class.
"Pom-Pom" director was a director for British anti-aircraft guns on British warships of the 1930s into the Second World War.
The Western Electric M-33 Antiaircraft Fire Control System was an X-Band "Gunfire Control Radar", for aiming antiaircraft artillery by computer control. Developed for mobility via 3 trailers, the "M-33 system could compute, for the 90-mm. and 120-mm. guns, firing data for targets with speeds up to 1,000 mph", and for targets at 120,000 yards had similar gun laying accuracy as "SCR-584 type radars" at 70,000 yards. The system included a telescopic "target selector" on a tripod near the guns for additional measurement of aircraft "azimuth and elevation data [to] be transmitted to the computer and utilized as gun directing data."
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