Magnetic anomaly detector

Thalen's "The Examination of Iron Ore Deposits by Magnetic Measurements", published in 1879, was the first scientific treatise describing this practical use.

[2] Magnetic anomaly detectors employed to detect submarines during World War II harnessed the fluxgate magnetometer, an inexpensive and easy to use technology developed in the 1930s by Victor Vacquier of Gulf Oil for finding ore deposits.

[3][4] MAD gear was used by both Japanese and U.S. anti-submarine forces, either towed by ship or mounted in aircraft to detect shallow submerged enemy submarines.

[6] To reduce interference from electrical equipment or metal in the fuselage of the aircraft, the MAD sensor is placed at the end of a boom or on a towed aerodynamic device.

Unlike sonar it is not impacted by meteorological conditions; indeed above sea state 5, MAD may be the only reliable method for submarine detection.

MAD rear boom on P-3C
The SH-60B Seahawk helicopter carries a yellow and red towed MAD array known as a "MAD bird", seen on the aft fuselage
A Soviet Tu-142MK (with MAD located in aft-facing fin-top fairing) escorted by US Navy Lockheed P-3C (MAD located in projection at base of tail), March 1986
PAC P-750 XSTOL geosurvey aircraft with a MAD stinger in Upernavik , Greenland