Under Crowsnest, all 30 of the HM2s will be fitted for the Crowsnest. Ten system sets will be purchased with eight Merlins to be fitted out at any one time. A critical part of the specification is that the role change from ASW and AEW must take 24 hr. or less.
Some options are offered. The first is the AgustaWestland/Thales concept of simply reusing the current Searchwater radars and mounting them from the rear of the Merlin with the radar mounted on a hinge that drops down below the aircraft. But Royal Navy Merlins are not fitted with a rear ramp, so Thales and AgustaWestland are studying an option that would see the radar lowered into the airflow on the rotorcraft's port side on two rails. Navy officials are concerned that the method may not meet the 24-hr. role-change requirement. However, they like that the system, because it is already owned by the Defense Ministry, is relatively low-cost. Also, it can be transplanted from one platform into the other.
The alternative is Lockheed Martin's Vigilance system. This uses a pair of Northrop Grumman AN/APG-81 active, electronically scanned array radars from the F-35 Lightning II, fitted in pods, one on each side of the aircraft. Each array is capable of providing 120 deg. of coverage. To achieve the full 180 deg., the radar will be mounted on a 30-deg. pintle.
Lockheed Martin say a production pod would weigh roughly the same as an air-launched torpedo and could be installed and removed from the aircraft in less than 2 hr. The company also asserts the system would be “plug and play” given its involvement in the development of the Merlin Mk2's mission system. A Merlin fitted with a prototype Vigilance pod is due to fly in the U.K. imminently.
Although not offered for Crowsnest, the team also studied and eliminated the configuration of the Italian navy's AEW mission-configured EH101s, which have a Selex Galileo Heliborne Early Warning 748 surveillance radar fitted in an enlarged radome under the forward fuselage.
Royal Navy commanders will also have to decide what to do with the experienced tactical mission commander and tactical aircraft control officers, who will have no platform to fly on after 2016.
Consideration is being given to sending personnel to the U.S. to join Navy E-2 Hawkeye units, similar to Project Seedcorn, in which people from the BAE Systems Nimrod maritime patrol aircraft community flew with other air forces to maintain their MPA operations skills following the cancellation of the Nimrod MRA4 program in 2010.