MAD stands for Magnetic Anomaly Detector. How is it used?

• A. Magnetic Acceleration Device; used to increase submarine speed underwater.
• B. Magnetic Anomaly Detector; used by aircraft to locate submarines by detecting magnetic disturbances.
• C. Mechanical Anomaly Detector; used to measure hull stress.
• D. Magnetic Alignment Device; used by helicopters to align with sub sil.

Answer: (B)

The idea being tested is how a Magnetic Anomaly Detector is used in anti-submarine warfare. MAD devices are highly sensitive magnetometers carried on aircraft. They measure the Earth’s magnetic field as the plane flies over ocean areas and look for distortions caused by a submarine’s ferromagnetic hull and equipment. Those magnetic disturbances stand out against the normal field, guiding the crew to where a submarine may be located and where sonar searches should focus. Submarines often try to reduce their magnetic signature with degaussing, but some anomaly is still detectable, especially at lower altitudes.

This is why the option describing use by aircraft to locate submarines by detecting magnetic disturbances best fits. The other choices describe non-existent or unrelated uses, so they don’t match what MAD actually does.