Olympus by HMCS Calgary in 1997. They can do this at significantly greater ranges than is possible with the ship's own sensor range. The use of a helicopter with active sonar extends the ship's antisubmarine detection range out past 100 nm and, when used effectively, allows for the detection, tracking and localization of hostile submarines as well as the delivery of weapons on a hostile submarine at far greater range than the submarine's torpedoes. This is particularly important when forces are in transit. Helicopters are not vulnerable to submarine torpedoes and therefore are the platform of choice to prosecute submarines.
Helicopters are able to reposition four times more quickly than ships.
This permits the rapid concentration of additional sensors and weapons on a sonar contact. Helicopters can be used to insert a ship's boarding team when the use of a ship's boat is impossible due to weather and sea state. Operations involving the extraction of combatants or non-combatants from countries or situations where there are no airfields, or where the use of an airfield is simply impractical, can be conducted with helicopters. In some cases, the only way to get a helicopter close enough to conduct the operation is from a sea-based unit. In the Persian Gulf helicopters conduct mine reconnaissance ahead of the ship searching for floating or mines lurking just below the surface of the water.