AgustaWestland has received a $750 million contract to upgrade the UK’s Merlin helicopter fleet for amphibious operations.

The RAF’s current fleet of AgustaWestland EH101 Merlin Mk. 3 and Mk. 3A helicopters will undergo the upgrade to the Mk. 4/4A standard for the U.K. Royal Navy’s amphibious Commando Helicopter Force (CHF).

The upgraded Merlins will be used to replace the aging Westland Sea King Mk. 4 currently in use by the CHF, which will exit service along with all other Sea Kings in the U.K. inventory by the end of March 2016.

A folding main rotor head will be fitted. The aircraft will also be given strengthened landing gear, deck lashing mounting points and a new fast-roping point. In the cockpit, the aircraft will be refitted with the avionics suite used in the update of the Royal Navy’s current fleet of Merlin helicopters used for anti-submarine and anti-surface warfare. Several of those aircraft are already in service. The program will also include obsolescence updates to improve maintainability and reliability.