This “confidential” Cold War-era United States Navy training film follows the Sonobuoy Indicator Group AN/AQA-1. The expendable sonobuoy was developed during World War II in response to the devastating destruction of Allied shipping in the Atlantic caused by German U-boats. The simple radio-linked listening device, thrown out of an aircraft, proved revolutionary. The indicator is shown at mark 01:18 as the narrator explains its operation and types, including the Range-Only Echo-Ranging AN/SSQ-15, the Directional Listening AN/SSQ-20, and the Non-Directional Listening AN/SSQ-2-b Type, as the trio are illustrated on the screen. Subsequent illustrations show exactly how the equipment works in painstaking detail, with each type of sonobuoy discussed starting at mark 03:54 with the Range-Only Echo-Ranging sonobuoy. As the film rolls on the narrator continues to explain various operations including how issues such as using two types of sonobuoys — such as the Range-Only Echo-Ranging AN/SSQ-15 and the Directional Listening AN/SSQ-20 — are used in tandem. The Non-Directional Listening sonobuoy is address starting at mark 14:19. “Your ability to properly operate the equipment in the Sonobuoy Indicator Group may mean the difference between an unsuccessful or a successful ASW mission,” the narrator says as the film comes to an end.
A sonobuoy (a portmanteau of sonar and buoy) is a relatively small buoy (typically 13 cm or 5 in, in diameter and 91 cm or 3 ft long) expendable sonar system that is dropped/ejected from aircraft or ships conducting anti-submarine warfare or underwater acoustic research. The buoys are ejected from aircraft in canisters and deploy upon water impact. An inflatable surface float with a radio transmitter remains on the surface for communication with the aircraft, while one or more hydrophone sensors and stabilizing equipment descend below the surface to a selected depth that is variable, depending on environmental conditions and the search pattern. The buoy relays acoustic information from its hydrophone(s) via UHF/VHF radio to operators on board the aircraft. Early sonobuoys had limited range, limited battery life and were overwhelmed by the noise of the ocean. They first appeared during world war II, in which they first were used in July 1942 by RAF Coastal Command under the code name 'High Tea', the first squadron to use them operationally being No. 210 Squadron RAF, operating Sunderlands. They were also limited by the use of human ears to discriminate man-made noises from the oceanic background. However, they demonstrated that the technology was viable. With the development of better hydrophones, the transistor and miniaturization, and the realization that very low frequency sound was important, more effective acoustic sensors followed. The sonobuoy went from being an imposing six feet tall, two feet diameter sensor to the compact suite of electronics it is today.
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This film is part of the Periscope Film LLC archive, one of the largest historic military, transportation, and aviation stock footage collections in the USA. Entirely film backed, this material is available for licensing in 24p HD, 2k and 4k. For more information visit http://www.PeriscopeFilm.com