Denmark is buying twelve American MH-60R Seahawk anti-submarine helicopters. This is a navalized version of the 11 ton U.S. Army UH-60. Denmark will use the MH-60Rs for search and rescues, as well as for ASW (Anti-Submarine Warfare). This involves using computers, sonar and radar to search for submarines. This work involves staring at a screen most of the time, while manipulating the sensors and computers to detect and locate subs. Once you have a solid location fix, you can launch a torpedo and sink the enemy vessel.
The MH-60R uses a sonar that operates in active (broadcasting) and passive (just listening) mode. This is a dipping sonar, which is lowered into the water from the helicopter using a 806 meter (2,500 foot) cable and winch. The MH-60R is also equipped with a radar system for detecting subs on the surface, or just beneath the surface (with only the periscope or schnorkel, which provides air for the diesel engine, and gets rid of the exhaust fumes). The sonar system consists of a dipping sonar and sonobuoys, that are dropped and communicate wirelessly.
For search and rescue work, the sonar and all its associated electronics is removed, but the radar stays. The MH-60 can hover low enough to deploy a line to people in the water, and winch them aboard.
Denmark has long used British helicopters, and still has bought four Westland EG101 Merlins, along with older Super Lynx models. The Lynxs are to be refurbished, and are currently so worn out that less than half of them are available for service at any one time.