Autolycus ( submarine detector ) Autolycus was a method for detecting submerged submarines from aircraft . It attempted to detect exhaust fumes from their diesel engines . It was developed by the British during the early Cold War period . The first version of Autolycus was deployed on Shackleton aircraft in the mid - 1950s , with an improved version re - appearing in the mid - 1960s . Submarines . During WWII , the first submarine snorkel s came into service . These allowed diesel submarines to operate near the surface , using their diesel engines , and without being seen by surface search radar . Designs such as the German type XXI U - boat were the first submarines designed to operate " primarily " submerged , rather than as submersibles that navigated on the surface and could submerge as a means to escape detection or launch an attack . After WWII , this emphasis on submerged operation , battery capacity and higher submerged speed continued . In the US , the GUPPY program rebuilt wartime submarines to emphasise this . New Soviet Union submarines , primarily of the " Whiskey " class , were based on the four Type XXIs that were assigned to them by the Potsdam Agreement . In the 1950s , the Fleet Air Arm were patrolling the North Sea and the GIUK gap for patrol and potentially anti - submarine warfare in search of Whiskey , Zulu and Foxtrot submarines . Patrol aircraft operated from RAF Ballykelly in Northern Ireland . A means was needed for the initial detection of submarines in the area . Once detected , other methods such as radar or sonobuoy hydrophone s could be used to track and target the contact . Operation . Autolycus was an ion - mobility spectrometer ( IMS ) . This is an early technique of extreme sensitivity and was a major technique for the initial detection of an unseen submarine . An IMS measures how fast a given ion moves in a uniform electric field through a given atmosphere . The spectrometer separates ions by shape and charge , so that different species arrive at the detector at different times . Typically this is used to produce a mobility profile characterising the sample . For Autolycus , a boxcar integrator sampled the times for known markers within diesel exhaust . Withdrawal . Autolycus was withdrawn for a number of reasons . The most immediate one was the withdrawal of the Shackleton carrier aircraft and their replacement with the Nimrod MR1 . The Nimrod was equipped with a Magnetic Anomaly Detector ( MAD ) tail boom . MAD was considered to be more capable than the Autolycus approach and could also detect submerged submarines operating without diesels or the increasing threat from nuclear submarines . MAD had not been successfully fitted to the Shackleton , possibly because of interference problems from the piston engines and their ignition system . Although the main submarine threat at the time of Autolycus ' withdrawal was still the diesel - engine Golf and Juliett class submarines , increasing numbers of the nuclear - powered Hotel and Echo II were in service in this region . As these did not need to snorkel and did not produce diesel exhaust they were effectively undetectable by either the Shackleton ' s Autolycus or its ASV Mk 13 radar . One of the cited limitations for Autolycus was a lack of discrimination between submarine exhaust , trawlers and on - shore sources . In practice this does not appear to have been a major limitation as it was used for initial detection , not identification or tracking .