Sikorsky Aircraft Corp., a subsidiary of United Technologies Corp., has delivered the 400th MH-60 Seahawk helicopter to the US Navy. The milestone consists of 166 MH-60R anti-submarine and anti-surface warfare helicopters, and 234 MH-60S utility/armed helicopters.

MH-60S (“Sierra”) helicopters carry supplies and sailors between ships, and protect U.S. ships from surface threats in an armed configuration. Sierra aircraft are expected to take on an airborne mine countermeasures role starting in 2014.

MH-60R (“Romeo”) helicopters employ radar, acoustic sonar, communications links, torpedoes and air-to-surface missiles for the anti-surface and anti-submarine warfare roles.

Sierra aircraft, which entered US Navy service in 2002, will remain in full rate production through 2015 as part of a currently planned production run of 275 aircraft. Romeo helicopters, operational since 2006, are currently scheduled to remain in production through 2017 to meet the Navy’s 291 intended aircraft buy. The two aircraft models have accumulated a combined 660,000 flight hours to date.

Sikorsky produces the MH-60R/S Seahawk aircraft models on separate production lines at its final assembly facility in Stratford, Connecticut. Avionics prime contractor Lockheed Martin performs all mission systems integration for Romeo aircraft at its Mission Systems and Training facility in Owego, New York, and also produces the digital cockpit common to both Romeo and Sierra models.