Photograph: AgustaWestland Merlin HM.2 (ZH831) by Paul Cremin on 22 July 2024 at the Royal International Air Tattoo, RAF Fairford, taken with a Canon EOS 7D Mk II and a Canon 100–400mm zoom lens at 300mm, f/14, 1/160 sec, ISO 100.
Royal Navy Merlin ZH831 (Construction Number 50053) is one of the most historically significant airframes in the UK's maritime helicopter fleet. It served as the pioneering test platform for major technological leaps, transitioning from a standard anti-submarine helicopter into the very first operational "Crowsnest" Airborne Early Warning (AEW) aircraft.
ZH831 completed its first flight on 4 February 1999 and was officially delivered to the Royal Navy on 11 March 1999. It was assigned to 700 Naval Air Squadron (NAS) at RNAS Culdrose by October 1999. Over the following decade, it rotated through front-line Anti-Submarine Warfare (ASW) units, including 820 NAS, 814 NAS, and 824 NAS (carrying code "583-CU" and nicknamed "Guinevere" during its time with 824).
In August 2000, ZH831 was selected as the very first Merlin to undergo the automatic main blade and tail rotor folding assembly modifications at Oldmixon, a critical capability for compact storage aboard Royal Navy warships.
In April 2009, the airframe was sent to AgustaWestland in Yeovil to be stripped down and rebuilt under the Merlin Capability Sustainment Programme (MCSP). It was converted into a Merlin HM.2 (completed in March 2014). This upgrade replaced its legacy 1990s computer architecture with a completely modernised glass cockpit, digital touchscreen displays, and enhanced processing systems.
ZH831 was chosen by the prime contractors Lockheed Martin, Thales and Leonardo to serve as the designated trials helicopter for the Crowsnest system. Crowsnest was designed to replace the retired Sea King ASaC7 fleet to provide carrier strike groups with long-range air, sea, and land surveillance.
On 28 March 2019, ZH831 successfully completed its official maiden flight from Leonardo’s airfield in Yeovil, fitted with the massive, distinctive external port-side radome. Following intensive aerodynamic, mechanical, and radar testing (evaluating the Thales Searchwater 2000 radar), the airframe was integrated back into 820 NAS. It deployed aboard HMS Queen Elizabeth to extend the fleet's defensive horizon against incoming missiles and enemy assets.
ZH831 remains a very active helicopter, which the Royal Navy showcases as a crown jewel of the Fleet Air Arm. The helicopter is seen here departing from the Royal International Air Tattoo at RAF Fairford.
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