Sonar aboard Knox-Class frigates helps Navy keep a close watch

http://www.etaiwannews.com/Taiwan/2004/09/20/1095646342.htm, While China's Navy with its large number of surface ships and submarines can be an intimidating force, the Taiwan Navy sees its own Knox-Class frigates of the 168 Fleet as an ace in the hole.

The Knox-Class frigates were specially designed to U.S. Navy requirements to counter the threat of the huge Russian submarine fleet during the Cold War, but after the 46 ships were decommissioned, the Taiwanese Navy acquired eight of them between 1992 and 1998.

The Knox-class frigate was designed with anti-submarine warfare in mind, the key technology being its sonar equipment. The ship carries an SQS-26 sonar at the front and an SQS-35 (V) variable depth sonar at the rear, as well as an SQR-18A (V) towed sonar.

“The sonar equipment on our ships is what any submarine fears the most,” said Captain Maio Yen-hsin of the Feng Yang 934, one of the eight Knox-class frigates leased from the U.S.

The sonar equipment on the ships has the ability to issue an underwater ping that could seem deafening to a submarine crew. According to the crews serving on another class of submarine in the Taiwan navy, the underwater ping from the Knox-class vessel sounds like a big bell over one's head being hit by a huge hammer.

“If we encounter any unknown submarines in our waters, we can chase them away, at all costs,” said Captain Maio.

According to former crew members of the 168 Fleet, when the Knox-class ships were first acquired by the Taiwan Navy, they were based at Kaohsiung's Tsoying military harbor on Taiwan's west coast where the sonar equipment was tested, but after the first test it became evident that the area was unsuitable as the pings were detected as far away as Okinawa on Japan's coastline. The frigates were moved to the deeper waters on the east coast and were later stationed at the Su Ao military harbor.

It is believed that Chinese submarines have been on the receiving end of the sonar equipment, as their Song-class and Ming-class vessels reportedly often try to sneak up on Taiwan's eastern coast.

A military officer disclosed that during a drill a few years ago in which two other types of Taiwan Navy submarines, the SS-793 Hai Lung and SS-794 Hai Hu played the role of an imaginary enemy, the Knox-class frigate detected a number of other vessels in Taiwan's waters. They were identified as Chinese, American, Japanese and Russian submarines. The Knox-Class frigates tracked them for a while, then “pinged” them, after which they fled. It was never quite clear why the foreign vessels were in that particular location at the time.

In another incident the Feng Yang 934 had a three-day encounter with a submarine of unknown nationality in 2000, just before the presidential elections. The unidentified vessel was located in waters off Hualien and Ilan. The crew of the Feng Yang 934 requested that the submarine identify itself but the request was ignored.

Following standard procedure, the Feng Yang 934 closely tracked the vessel. The crew of the submarine, in a surprising reaction, did not maintain the expected silence but rather could be heard giving loud orders in Chinese. It was deduced that it was a People's Liberation Army vessel, possibly of the Ming class.

On that occasion, the Feng Yang did not ping the submarine, choosing instead to protect the frequency of its sonar.

The Taiwan Navy headquarters, noting that the encounter was a rare one, sent other frigates such as the Cheng Kung 1101 and other Gearing-Class destroyers to monitor the situation that lasted three days.

The Knox-Class frigate is 134 meters long and 14.33 meters wide with a displacement of 4260 tons.