A RNZAF P-3K Orion; the magnetic anomaly dectector protrudes from the tail to minimise interference from the aircraft's avionics.

The SH-60B Seahawk helicopter carries an orange, towed MAD array known as a ‘MAD bird’, seen on the aft fuselage.

A magnetic anomaly detector (MAD) is a piece of equipment that is used to detect minute variations in the Earth's magnetic field. The term refers specifically to magnetometers used either by military forces to detect submarines—such a mass of ferromagnetic material disturbs the magnetic field and can be detected—or to a geomagnetic survey instrument used to search for minerals by the disturbance of the normal earth-field. Image File history File links From NZ govt records File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links From NZ govt records File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... The Royal New Zealand Air Force (RNZAF) is the air force arm of the New Zealand Defence Force. ... P-3 Orion The Lockheed P-3 Orion is a maritime patrol aircraft of the United States military used primarily for maritime patrol, reconnaissance, and anti-submarine warfare. ... Image File history File linksMetadata Download high resolution version (3008x2000, 570 KB) An SH-60B Seahawk helicopter and SH-60F Seahawk prepare to land on the flight deck of USS Kitty Hawk (CV 63). ... Image File history File linksMetadata Download high resolution version (3008x2000, 570 KB) An SH-60B Seahawk helicopter and SH-60F Seahawk prepare to land on the flight deck of USS Kitty Hawk (CV 63). ... Sikorsky SH-60B Seahawk The SH-60B is designed to operate as an integral fighting unit aboard specifically configured Oliver Hazard Perry (FFG-7) class Guided Missile Frigates, Spruance (DDG-963) class Destroyers, Kidd (DDG-993), class Guided Missile Destroyers and Ticonderoga (CG-47) class Guided Missile Cruisers. ... An anomaly is a deviation from the common rule. ... Current flowing through a wire produces a magnetic field (B, labeled M here) around the wire. ... A magnetometer is a scientific instrument used to measure the strength of magnetic fields. ... German UC-1 class World War I submarine A model of Gunter Priens Unterseeboot 47 (U-47), German WWII Type VII diesel-electric hunter-killer (SSK) submarine Inside of the Argonaute, showing the typical obstructed, tiny space of a post-WWII diesel attack submarine. ... Ferromagnetism is a phenomenon by which a material can exhibit a spontaneous magnetization, and is one of the strongest forms of magnetism. ... The cause of Earths magnetic field (the surface magnetic field) is not known for certain, but is possibly explained by dynamo theory. ... There are several uses of the word survey, relating to two primary meanings: land surveying; and statistical surveys of people or other items, such as animals, stars, or messages. ... Minerals are natural compounds formed through geological processes. ...

History

Magnetic anonmaly detectors were first employed to detect submarines during World War II. MAD gear was used by both Japanese and U.S. anti-submarine forces, either towed by ship or mounted in aircraft to detect shallowly submerged enemy submarines. After the war, the U.S. Navy continued to develop MAD gear as a parallel development with sonar detection technologies.

Operation

To reduce interference from electrical equipment aboard anti-submarine aircraft the 'MAD head' is placed out from the aircraft on a boom or is a towed aerodynamic device. Even so the submarine must be very near the aircraft's position (and close to the sea surface) to detect the change or anomaly. The detection range is normally related to the distance between the sensor and the submarine. The size of the submarine, its orientation in the Earth's magnetic field, and its hull material composition also determines the detection range. MAD devices are usually mounted on aircraft. German UC-1 class World War I submarine A model of Gunter Priens Unterseeboot 47 (U-47), German WWII Type VII diesel-electric hunter-killer (SSK) submarine Inside of the Argonaute, showing the typical obstructed, tiny space of a post-WWII diesel attack submarine. ... Airbus A380 An aircraft is any machine capable of atmospheric flight. ...

Function

There is some misunderstanding of the actual detection of submarines in water using the MAD boom system - ostensibly magnetic moment displacement is the main disturbance, yet submarines are detectable even when lying parallel with the earth's magnetic field, and despite construction with non-ferromagnetic hulls , in particular the Soviet-Russian Alfa-class attack submarine, whose hull is constructed out of Titanium to both give dramatic submerged performance and protection from detection by MAD sensors - to which it is still detectable. Soviet redirects here. ... General Name, Symbol, Number titanium, Ti, 22 Chemical series transition metals Group, Period, Block 4, 4, d Appearance silvery metallic Atomic mass 47. ...

The Alfa's detectability has led analysts not privy to the actual workings of the MAD sensor to deduce that its very name is a form of intelligence smokescreen, so effective that the Soviet Union to construct the Alfa and even consider building the Typhoon-class SSBN out of titanium at one point. Since titanium structures are detectable, MAD sensors do not directly detect deviations in the earth's magnetic field. Instead, they may be described as long-range electric and electromagnetic field detector arrays of great sensisitivity. It has been proposed below that SSBN be renamed and moved to Ballistic missile submarine. ...

An electric field is set up in conductors experiencing a variation in physical environmental conditions, providing that they are contiguous and posess sufficient mass. Particularly in submarine hulls, there is a measurable temperature difference between the bottom and top of the hull producing a related salinity difference, as salinity is affected by temperature of water. The difference in salinity sets up an electric potential, with the submarine hull acting as a conductor - and an electric field flows through the hull, as ions exchange charge as a flow of metal nuclei-bound free electron flow in the metal between the otherwise depth and temperature separated laminae of sea-water. In physics, an electric field or E-field is an effect produced by an electric charge (or a time-varying magnetic field) that exerts a force on charged objects in the field. ... Salinity is the saltiness or dissolved salt content of a body of water. ... Electric potential is the potential energy per unit of charge associated with a static (time-invariant) electric field, also called the electrostatic potential, typically measured in volts. ...

The resulting dynamic electric field produces an electromagnetic field of its own, and thus even a titanium hull will be detectable on a MAD scope, as will a surface ship for the same reason.

In the case of the "Pave Mace"/"Black Crow" system (see below), the same principle applies - the electric field of the truck coil is visible, rather than its magnetic disturbance, which is in itself a strong indication as to the true nature of the MAD sensor system's functions.

Other uses

For geomagnetic survey work the detector can be mounted on a long probe in front of the aircraft or be a towed device. A chart is produced that geologists can study to determine the location and extent of mineral deposits.

Another, similar use was by the original AC-130A Spectre gunships, which employed the "Pave Mace"/"Black Crow" magnetic anomaly detection system to detect truck ignition coils (hidden in heavy overhead jungles) during the Vietnam War. AC-130 deploying flares The AC-130 Gunship is an armed variant of the Lockheed C-130 Hercules. ... Combatants Republic of Vietnam United States Republic of Korea Thailand Australia New Zealand The Philippines Democratic Republic of Vietnam National Front for the Liberation of South Vietnam People’s Republic of China Commanders William Westmoreland Ho Chi Minh Strength ~1,200,000 (1968) ~520,000 (1968) Casualties South Vietnamese dead...

See also: Antisubmarine warfare Anti-submarine warfare is a term referring to warfare directed against submarines. ...