A director, also called an auxiliary predictor, is a

mechanical Mechanical may refer to: Machine * Machine (mechanical), a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement * Mechanical calculator, a device used to perform the basic operations ...

electronic Electronic may refer to: *Electronics, the science of how to control electric energy in semiconductor * ''Electronics'' (magazine), a defunct American trade journal *Electronic storage, the storage of data using an electronic device *Electronic co ...

computer that continuously calculates

trigonometric Trigonometry () is a branch of mathematics that studies relationships between side lengths and angles of triangles. The field emerged in the Hellenistic world during the 3rd century BC from applications of geometry to astronomical studies. ...

firing solutions for use against a moving target, and transmits targeting data to direct the weapon firing crew.

Naval warships

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 The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against Fr ...

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 Table Admiral Sir Frederic Charles Dreyer, (8 January 1878 – 11 December 1956) was an officer of the Royal Navy. A gunnery expert, he developed a fire control system for British warships, and served as flag captain to Admiral Sir John Jellicoe at ...

s 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 The Mark 1, and later the Mark 1A, Fire Control Computer was a component of the Mark 37 Gun Fire Control System deployed by the United States Navy during World War II and up to 1991 and possibly later. It was originally developed by Hannibal C. ...

. On

ship A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished ...

s 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.

Field artillery

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

theodolite A theodolite () is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes. The traditional use has been for land surveying, but it is also used extensively for building and ...

s 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.

Anti-aircraft

For anti-aircraft use, directors are usually used in conjunction with other fire control equipment, such as

height finder A height finder is a ground-based aircraft altitude measuring device. Early height finders were optical range finder devices combined with simple mechanical computers, while later systems migrated to radar devices. The unique vertical oscillating ...

s or

fire control radar A fire-control radar (FCR) is a radar that is designed specifically to provide information (mainly target azimuth, elevation, range and range rate) to a fire-control system in order to direct weapons such that they hit a target. They are sometime ...

s. 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 gun The 3"/50 caliber gun (spoken "three-inch fifty-caliber") in United States naval gun terminology indicates the gun fired a projectile in diameter, and the barrel was 50 calibers long (barrel length is 3 in × 50 = ). Different guns (identifi ...

s. The

Kerrison Predictor 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 ...

was also designed to be used with the

Bofors 40 mm gun Bofors 40 mm gun is a name or designation given to two models of 40 mm calibre anti-aircraft guns designed and developed by the Swedish company Bofors: *Bofors 40 mm L/60 gun - developed in the 1930s, widely used in World War II and into the 1990s ...

Example

The Bofors 40 mm gun (called a fire unit) used in its anti-aircraft role has the M5 director for its

fire-control system 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 ...

. 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 A platoon is a military unit typically composed of two or more squads, sections, or patrols. Platoon organization varies depending on the country and the branch, but a platoon can be composed of 50 people, although specific platoons may range ...

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 M7, M-7, or M.7 may refer to: Transportation Air * M7 Aerospace, a United States aerospace company * Macchi M.7, an Italian flying boat fighter in service from 1923 to 1930 * Miles M.7 Nighthawk, a 1930s British training and communications monopla ...

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 Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...

slant range In radio electronics, especially radar terminology, slant range or slant distance is the distance along the relative direction between two points. If the two points are at the same level (relative to a specific datum), the slant distance equals t ...

of the aerial target. Two observers then track the aircraft through a pair of

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...

s on opposite sides of the director. The trackers turn handwheels to keep the

crosshairs A reticle, or reticule also known as a graticule, is a pattern of fine lines or markings built into the eyepiece of an optical device such as a telescopic sight, spotting scope, theodolite, optical microscope or the screen of an oscilloscope ...

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 Ballistics may refer to: Science * Ballistics, the science that deals with the motion, behavior, and effects of projectiles ** Forensic ballistics, the science of analyzing firearm usage in crimes ** Internal ballistics, the study of the proc ...

conditions such as

air density The density of air or atmospheric density, denoted '' ρ'', is the mass per unit volume of Earth's atmosphere. Air density, like air pressure, decreases with increasing altitude. It also changes with variation in atmospheric pressure, temperature a ...

wind velocity In meteorology, wind speed, or wind flow speed, is a fundamental atmospheric quantity caused by air moving from high to low pressure, usually due to changes in temperature. Wind speed is now commonly measured with an anemometer. Wind speed a ...

and

wind direction Wind direction is generally reported by the direction from which it originates. For example, a ''north'' or ''northerly'' wind blows from the north to the south. The exceptions are onshore winds (blowing onto the shore from the water) and offsho ...

. If the director was not located near the gun sections, a correction for

parallax error Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...

could also be entered to produce even more accurate firing direction calculations. 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 Ammunition (informally ammo) is the material fired, scattered, dropped, or detonated from any weapon or weapon system. Ammunition is both expendable weapons (e.g., bombs, missiles, grenades, land mines) and the component parts of other weap ...

with timed

fuze In military munitions, a fuze (sometimes fuse) is the part of the device that initiates function. In some applications, such as torpedoes, a fuze may be identified by function as the exploder. The relative complexity of even the earliest fuze d ...

s, the director also provides the flight time for the projectile so the fuze can be set to

detonate Detonation () is a type of combustion involving a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations propagate supersonically through shock waves with s ...

close Close may refer to: Music * ''Close'' (Kim Wilde album), 1988 * ''Close'' (Marvin Sapp album), 2017 * ''Close'' (Sean Bonniwell album), 1969 * "Close" (Sub Focus song), 2014 * "Close" (Nick Jonas song), 2016 * "Close" (Rae Sremmurd song), 201 ...

to the target. Early anti-aircraft

artillery batteries In military organizations, an artillery battery is a unit or multiple systems of artillery, mortar systems, rocket artillery, multiple rocket launchers, surface-to-surface missiles, ballistic missiles, cruise missiles, etc., so grouped to faci ...

located the directors in the middle of the position, with the firing sections (guns) located at the corners of the position. Before the introduction of

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

searchlight A searchlight (or spotlight) is an apparatus that combines an extremely bright source (traditionally a carbon arc lamp) with a mirrored parabolic reflector to project a powerful beam of light of approximately parallel rays in a particular direc ...

s were used in conjunction with directors to allow night target engagement.

U.S. Army anti-aircraft directors

* T1 (wilson) director * T4 gun director used with

3-inch M1918 gun The 3-inch gun M1918 was a United States 3-inch anti-aircraft gun that entered service in 1918 and served until it was largely superseded by the 3-inch anti-aircraft gun M3 in 1930, though the M1918 remained with some National Guard units until ...

* T6 was built by

Sperry Corporation Sperry Corporation was a major American equipment and electronics company whose existence spanned more than seven decades of the 20th century. Sperry ceased to exist in 1986 following a prolonged hostile takeover bid engineered by Burroughs ...

in 1930 and standardized as the M2 director. * M3 was standardized from the T8 in 1934 * M4 was standardized in 1939 * M5 Gun Director Mechanical, a US-produced

, for use with

37mm Gun M1 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 gun was produced in a towed variant, or mounted along with two M2 machine guns on the M2/ M3 half-track, resul ...

and M1 40 MM ** M5A1 ** M5A2 * M7 gun director was standardized in 1941, and is similar to the M4 but added power control to the guns it is still described as a mechanical system. for use with 90 mm gun ** M7A1B1 ** M7A1B2 * T10 standardized as M9 gun director electrical for use with 90 mm gun produced by

Bell Labs Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by mult ...

** M9B1 * M10 gun director electrical for use with

120 mm M1 gun The 120 mm Gun M1 was the United States Army's standard super-heavy anti-aircraft gun during World War II and the Korean War, complementing the smaller and more mobile M2 90 mm gun in service. Its maximum altitude was about , which earned it ...

Naval directors

* Mark 1 *

MK 51 Fire Control System MK or mk may refer to: In arts, entertainment and media Fictional characters * Moon Knight, a Marvel Comics superhero * M.K., an '' ''Into the Badlands'' (TV series) character * Mary Katherine "M.K." Bomba, the protagonist in ''Epic'' (2013 fil ...

* Mark 56 * Mark 57 * Mark 58 * Mark 59 * Mark 92 * Type 6 director (PRC) File:Sea Sparrow Mark115 Fire Control Director.JPEG, A late

Cold War The Cold War is a term commonly used to refer to a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc. The term '' cold war'' is used because the ...

era

U.S. Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage o ...

Mark 115

Sea Sparrow RIM-7 Sea Sparrow is a U.S. ship-borne short-range anti-aircraft and anti-missile weapon system, primarily intended for defense against anti-ship missiles. The system was developed in the early 1960s from the AIM-7 Sparrow air-to-air missile as a ...

fire control system director on board a . File:Cardiff gunnery.JPG, A modern

director on board a

Type 42 destroyer The Type 42 or ''Sheffield'' class, was a class of fourteen guided-missile destroyers that served in the Royal Navy.Marriott, Leo: ''Royal Navy Destroyers since 1945'', , Ian Allan Ltd, 1989 A further two ships of this class were built for and s ...

. File:Mk51 Director.jpg, A U.S. Navy Mark 51 director for Bofors 40 mm guns, circa 1958. File:USS Hornet director front.jpg, A Cold War era U.S. Navy MK-56 director on board .

Surviving examples

South African National Museum of Military History The South African National War Museum in Johannesburg was officially opened by Prime Minister Jan Smuts on 29 August 1947 to preserve the history of South Africa's involvement in the Second World War. In 1975, the museum was renamed the South Af ...

- Number 1 Mark II Predictor *

Powerhouse Museum The Powerhouse Museum is the major branch of the Museum of Applied Arts & Sciences (MAAS) in Sydney, the others being the historic Sydney Observatory at Observatory Park, Sydney, Observatory Hill, and the newer Museums Discovery Centre at Castle ...

- Vickers No.1 anti-aircraft predictor, 1942 * , museum ship, Houston, Texas. Mark 51 anti-aircraft directors.

Notes

References

* TM 9-2300 Standard Artillery and Fire Control Materiel dated 1944 * Brooks, Brian L., ''Antiaircraft command: Preserving the history of U.S.Army antiaircraft artillery of World War II'', Directors and height finders

* Lone Sentry.com, ''German Antiaircraft Artillery, Military Intelligence Service, Special Series 10, Feb. 1943'', U.S. War Department, 1943 * Skylighters, A Beginner's Guide to the Skylighters, WW II Antiaircraft Artillery, Searchlights, and Radar
Skylighters.org
January 10, 2004 * Brown, Louis, ''A Radar History of World War II: Technical and Military Imperatives'', CRC Press, 1999 * ''Journal of the United States Artillery'', v. 47, Artillery School (Fort Monroe, Va.), Coast Artillery Training Center (U.S.), 1917 * Dow Boutwell, William, Brodinsky, Ben, Frederick, Pauline, Pratt Harris, Joseph, Nixon, Glenn, Robertson, Archibald Thomas, ''America Prepares for Tomorrow; the Story of Our Total Defense Effort'', Harper and brothers, 1941 * Evans, Nigel F.

* Bennett, Stuart, ''A History of Control Engineering, 1930–1955'', IET, 199
''The Coast Artillery Journal''
May/June 1935

External links

Director Firing Handbook index from HMS Dreadnought project

* http://web.mit.edu/STS.035/www/PDFs/sperry.pdf * https://books.google.com/books?id=sExvSbe9MSsC&printsec=frontcover&dq=Between+Human+and+Machine * https://books.google.com/books?id=T-IDAAAAMBAJ&pg=PA801&dq=m16+gun+data+computer&as_brr=1

* ttp://www.navsource.org/archives/01/57o.htm Director section of Mark 1 Mod 1 computer operations at NavSource.org {{DEFAULTSORT:Director (Military) Applications of control engineering Artillery components Ballistics * Anti-aircraft guns of the United States Artillery operation