User:Usnavfac

The Integrated Undersea Surveillance system (IUSS) was conceived back in the 1950's. By the early 1980's the US Navy had distributed undersea surveillance arrays - often miss called SOSUS arrays around the World. In the North Atlantic a number of arrays were in place. They were referred to by a 4 number code such as 7116 which was situated north of the Iceland Faeroes gap. The array's operated originally from RAF Brawdy in Wales - now at RAF St.Mawgan - from South to North were 7123, 7122, 7121, 7114, 715 and 7116 with an FDS system in a horse shoe shape, fixed just North of Ireland opposite Faslane and Holy Lock naval bases.

The Royal Navy worked these arrays jointly with the US Navy, but the Royal Navy also operated the Innkeeper array just inside the Gibraltar straits of the Med. The array rather that stretching across the entrance, ran the length of the entrance with 24 beams - formed from hydrophones placed on the sea bed. Ice maiden also operated in the Norwegian sea with arrays also running out of Iceland 7112, 7111, and from Norway. Additionally Ice arrays were placed on the permanent Ice pack to allow detection below the Ice.

Most of the arrays were 24 beam arrays, allowing long range detection of contacts both surface and subsurface. Ranges of some 4000 nautical miles were common in ideal conditions – particularly with noisy Type 1 and 2 soviet submarines (Hotel, Echo and November, Charlie and Victor classes). Although some older Type 3 hulls were also detected at similar ranges (Yankee I/II and Delta I/II). The more common detection ranges were within 1,000 NM.

Quieter western submarines were detected up to 1,000 plus NM particularly during acceleration.

Discrete tonal frequencies were the main causes of detection with SSTGs at 50 cycles (50Hz), and harmonics thereof. Soviet gearing of 10.89:1 on HEN classes and 17.02 to 1 on the C,V,Y,D classes were also common. Often the planetary gearing of the type 2’s and 3’s could be detected with individual teeth on sun and ring gears being predominant. 209 teeth on the ring and 92 on the sun. The later Type 4 (Papa), Type 5’s (Alfa), Type 6 Oscar and 7’s Typhoon could be detected quite easily. Even the MPTA’s of the Alfa was detectable with a 144 pole ration on the electric drive motor giving a 12 to 1 reduction between MPTA (main propulsion turbo alternator) and shaft. Blade and shaft counts were commonly seen, even with the move to seven blades on the VIII and newer boats. However as newer boats became quieter flow induced resonance from the hulls became more common. The Firs were complimented by HARS (high amplitude resonance) and HAIRS ((high amplitude internal resonance). These tonal frequencies were given off by hull deficiencies such as missing anechoic tiles or poor stream lining of the hull causing cavitation or water resonance in or around the hull.

Most vessels from all nations were detected and tracked throughout all the Worlds oceans and seas. However the arrays were no good for pin pointing contacts. Often they would be narrowed to within a few hundred square miles, were ships or submarines, supported by MPA’s (maritime patrol aircraft), would isolate the contacts down to a few hundred yards. Arrays ran out of Bermuda, Hawaii and Argencia, along with many other counties.

At their peak the Nato forces knew the location of every Soviet ship and submarine and practiced their subsequent destruction continually.