Autolycus or Sniffer [1] was a submarine detection system designed to detect diesel-engined submarines from aircraft. It was designed to detect exhaust fumes from their diesel engines. [2] Named after the mythical Greek, Autolycus, who took part in the search for the Golden Fleece, it was developed by the British during the early Cold War period. The first version of Autolycus was deployed on Avro Shackleton aircraft in the mid-1950s, with an improved version re-appearing in the mid-1960s. [3]
Until the end of the Second World War, submarines spent the majority of the time on the surface, powered by their diesel engines. They could submerge for only short periods during and after the attack. This made them easy to detect on radar, and by 1943, radar-equipped aircraft had made surface submarine operations difficult.[ citation needed ]
Just before the outbreak of the Second World War, the Royal Netherlands Navy introduced the first submarine snorkels, which provided air to the crew and the engines, allowing the submarine to remain submerged just below the surface. This allowed them to avoid most radars, as well as allowing them to approach convoys more closely on diesel, extending the range they could run on batteries. When Nazi Germany invaded and occupied the Netherlands in 1940 they also captured the latest Dutch O 21-class submarines equipped with snorkels, which the Germans then copied and started to use from 1943 onwards. Designs like the Type XXI U-boat were the first German submarines to operate primarily submerged.
After the Second World War, this emphasis on submerged operation, battery capacity and higher submerged speed continued. In the US, the GUPPY program rebuilt wartime submarines to emphasise these features. In the Soviet Union, the four Type XXIs that were assigned to them by the Potsdam Agreement formed the basis for their Whiskey class.
In the 1950s, the Fleet Air Arm were flying in 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. [3] A means was needed for the initial detection of submarines in the area. Once detected, other methods such as radar or sonobuoy hydrophones could be used to track and target the contact.
Autolycus was an ion-mobility spectrometer (IMS). [4] This is an early technique of extreme sensitivity and was a major technique for the initial detection of an unseen submarine. [2]
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. Display to the operator was on a continuous paper printout. [5]
The Autolycus technique was developed and first tested during the Second World War on warships. [6] After the war, the Mk. II version became light enough for airborne use. Fast-moving aircraft were better able to locate submarines by travelling in search patterns.
Early Mk II versions of Autolycus suffered from calibration difficulties in high humidity and stopped working altogether in rain. These problems were reduced in the Mk. III version. [6] This also had better time discrimination, giving better position fixes. On the Shackleton the air scoop for the system was located on the port side of the aircraft nose.
As Autolycus detected fumes from the submarine, rather than sound emanating from the hull, it could detect the passage of a submarine for some time after it had passed. This aided searching, as it did not need to pass directly overhead. A zig-zag search pattern was flown, passing at right-angles over the likely direction of submarine movements. When an exhaust plume was detected, the aircraft would begin to fly a tracking pattern of progressively shorter zig-zags. Each crossing of the plume trail would be plotted, giving a map plot of the submarine's likely track. As the track was narrowed down, the aircraft would switch sensors to a more precise method, such as centimetric radar or dropping sonobuoys before potentially closing for an attack. [7]
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. Nimrod was fitted with Autolycus, but this legacy equipment was no longer considered to be a first-line technique and so it was not integrated into the new tactical display system, based on an Elliott 920 digital computer. [8]
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.[ citation needed ]
Although the main submarine threat at the time of Autolycus' withdrawal was still the Soviet diesel-engine Golf and Juliett class submarines, increasing numbers of the nuclear-powered Hotel and Echo II were in service in this region. [9] 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. [10]
One of the cited limitations for Autolycus was a lack of discrimination between submarine exhaust, trawlers and on-shore sources. [2] In practice this does not appear to have been a major limitation as it was used for initial detection, not identification or tracking. [11]
A submarine is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine and the wet sub. Submarines are referred to as boats rather than ships irrespective of their size.
The Hawker Siddeley Nimrod is a retired maritime patrol aircraft developed and operated by the United Kingdom. It was an extensive modification of the de Havilland Comet, the world's first operational jet airliner. It was originally designed by de Havilland's successor firm, Hawker Siddeley; further development and maintenance work was undertaken by Hawker Siddeley's own successor companies, British Aerospace and, later, BAE Systems.
A magnetic anomaly detector (MAD) is an instrument used to detect minute variations in the Earth's magnetic field. The term refers specifically to magnetometers used by military forces to detect submarines ; military MAD equipment is a descendant of geomagnetic survey or aeromagnetic survey instruments used to search for minerals by detecting their disturbance of the normal earth-field.
The Grumman S-2 Tracker was the first purpose-built, single airframe anti-submarine warfare (ASW) aircraft to enter service with the United States Navy. Designed and initially built by Grumman, the Tracker was of conventional design — propeller-driven with twin radial engines, a high wing that could be folded for storage on aircraft carriers, and tricycle undercarriage. The type was exported to a number of navies around the world. Introduced in 1952, the Tracker and its E-1 Tracer derivative saw service in the U.S. Navy until the mid-1970s, and its C-1 Trader derivative until the mid-1980s, with a few aircraft remaining in service with other air arms into the 21st century. Argentina and Brazil are the last countries to still use the Tracker.
The Avro Shackleton is a British long-range maritime patrol aircraft (MPA) which was used by the Royal Air Force (RAF) and the South African Air Force (SAAF). It was developed by Avro from the Avro Lincoln bomber, which itself had been a development of the famous wartime Avro Lancaster bomber.
A maritime patrol aircraft (MPA), also known as a patrol aircraft, maritime reconnaissance aircraft, maritime surveillance aircraft, or by the older American term patrol bomber, is a fixed-wing aircraft designed to operate for long durations over water in maritime patrol roles — in particular anti-submarine warfare (ASW), anti-ship warfare (AShW), and search and rescue (SAR).
The Balao class was a design of United States Navy submarine used during World War II, and with 120 boats completed, the largest class of submarines in the United States Navy. An improvement on the earlier Gato class, the boats had slight internal differences. The most significant improvement was the use of thicker, higher yield strength steel in the pressure hull skins and frames, which increased their test depth to 400 feet (120 m). Tang actually achieved a depth of 612 ft (187 m) during a test dive, and exceeded that test depth when taking on water in the forward torpedo room while evading a destroyer.
Tench-class submarines were a type of submarine built for the United States Navy (USN) between 1944 and 1951. They were an improvement over the Gato and Balao classes, only about 35 to 40 tons larger, but more strongly built and with a slightly improved internal layout. One of the ballast tanks was converted to carry fuel, increasing range from 11,000 nautical miles to 16,000 nautical miles. This improvement was also made on some boats of the previous two classes. Further improvements were made beginning with SS-435, which are sometimes referred to as the Corsair class. Initial plans called for 80 to be built, but 51 were cancelled in 1944 and 1945 when it became apparent that they would not be needed to defeat Japan. The remaining 29 were commissioned between October 1944 (Tench) and February 1951 (Grenadier). The last submarine of the Tench class, as well as the last submarine which served during World War II, remaining in service with the U.S. Navy was USS Tigrone (AGSS-419) which was decommissioned on 27 June 1975.
The Naxos radar warning receiver was a World War II German countermeasure to S band microwave radar produced by a cavity magnetron. Introduced in September 1943, it replaced Metox, which was incapable of detecting centimetric radar. Two versions were widely used, the FuG 350 Naxos Z that allowed night fighters to home in on H2S radars carried by RAF Bomber Command aircraft, and the FuMB 7 Naxos U for U-boats, offering early warning of the approach of RAF Coastal Command patrol aircraft equipped with ASV Mark III radar. A later model, Naxos ZR, provided warning of the approach of RAF night fighters equipped with AI Mk. VIII radar.
A sonobuoy is a relatively small buoy – typically 13 cm (5 in) diameter and 91 cm (3 ft) long – expendable sonar system that is dropped/ejected from aircraft or ships conducting anti-submarine warfare or underwater acoustic research.
An anti-submarine weapon (ASW) is any one of a number of devices that are intended to act against a submarine and its crew, to destroy (sink) the vessel or reduce its capability as a weapon of war. In its simplest sense, an anti-submarine weapon is usually a projectile, missile or bomb that is optimized to destroy submarines.
The Canadair CP-107 Argus is a maritime patrol aircraft designed and manufactured by Canadair for the Royal Canadian Air Force (RCAF). The Argus served throughout the Cold War in the RCAF's Maritime Air Command and later the Canadian Force's Maritime Air Group and Air Command.
Anti-submarine warfare is a branch of underwater warfare that uses surface warships, aircraft, submarines, or other platforms, to find, track, and deter, damage, or destroy enemy submarines. Such operations are typically carried out to protect friendly shipping and coastal facilities from submarine attacks and to overcome blockades.
The R600A Metox, named after its manufacturer, was a pioneering high-frequency radar warning receiver (RWR) used by the German forces on U-boats from 1942-45. It was initially installed to receive signals used by British radars.
A submarine snorkel is a device which allows a submarine to operate submerged while still taking in air from above the surface. British Royal Navy personnel often refer to it as the snort. A concept devised by Dutch engineers, it was widely used on German U-boats during the last year of World War II and known to them as a Schnorchel.
Geophysical MASINT is a branch of Measurement and Signature Intelligence (MASINT) that involves phenomena transmitted through the earth and manmade structures including emitted or reflected sounds, pressure waves, vibrations, and magnetic field or ionosphere disturbances.
Orange Harvest was an ESM receiver fitted to marine patrol Avro Shackletons during the Cold War.
Yellow Duckling was an early development of an infrared linescan camera, developed for the detection of submarines during the Cold War. The name is one of the series of British Rainbow Codes.
Radar, Air-to-Surface Vessel, or ASV radar for short, is a classification used by the Royal Air Force (RAF) to refer to a series of aircraft-mounted radar systems used to scan the surface of the ocean to locate ships and surfaced submarines. The first examples were developed just before the opening of World War II and they have remained a major instrument on patrol aircraft since that time. It is part of the wider surface search radar classification, which includes similar radars in ground and ship mountings.
Air-Sea Warfare Development Unit RAF (ASWDU) was a research and development unit of the Royal Air Force, within RAF Coastal Command, it was operational from December 1940 and disbanded in April 1970.
There are two other methods of detecting a submerged submarine from the air. The first, called Autolycus in Britain and Sniffer in America, is a device which detects the fumes emitted by a diesel-powered submarine into the atmosphere. It is not a primary means of detection and at best it can only tell the aircraft that a diesel submarine was recently present (and has now dived), or is present but for some reason the snorkel has not been detected. As more and more submarines become nuclear powered the device will lose its already limited usefulness.