What is a "sniffer" in anti-submarine warfare?

Short answer

A device that detected from the air the gases a diesel submarine released into the atmosphere. The British Autolycus, developed in the early years of the Cold War, was an ion mobility spectrometer. It debuted on the Avro Shackleton in the mid-1950s, and the Nimrod carried it as legacy equipment.

Published: November 5, 2026 · Updated: November 5, 2026 · Edited by Above Ten Thousand · Editorial policy

What is a "sniffer" in anti-submarine warfare?

Hawker Siddeley Nimrod in flight, Manston Kent 1981Les Chatfield from Brighton, England (CC BY), vía commons

An exhaust-gas detector

Autolycus was a device that detected the gases a diesel submarine released into the atmosphere. It was developed by the British in the early years of the Cold War and was designed to locate diesel-powered submarines from an aircraft. Technically it was an ion mobility spectrometer. The first version was deployed aboard Avro Shackletons in the mid-1950s. Its weak point was its inability to distinguish between a submarine's exhaust, that of fishing boats, and sources on land.

Aboard the Nimrod

The Nimrod carried Autolycus, but as legacy equipment no longer considered a front-line technique, so it was not integrated into the new tactical display system. The aircraft was used in anti-submarine warfare operations, aimed at detecting the presence of Soviet submarines and tracking their movements. Its sensor systems included radar, ESM radar detection and sonar, as well as a MAD (magnetic anomaly detection) boom.

A converted civilian airframe

The Nimrod was an extensive modification of the de Havilland Comet. The fuselage changed significantly: an internal weapons bay, a lengthened nose for the radar, a new tail with electronic warfare sensors mounted in a bulky fairing, and the aforementioned MAD boom. Rolls-Royce Spey turbofans were fitted for their better fuel efficiency, particularly at the low altitudes required for maritime patrol.