In the carriers and frigates, the larger Merlin anti-submarine warfare helicopter is used. There are 30 Merlin HM2 helicopters in service. In late 2009 the Fleet Air Arm retired its remaining Sea King HC4 helicopters, their place being taken by Merlins upgraded and transferred from the Royal Air Force (RAF). The future AEW capability of the FAA is the "Crowsnest" programme, which will replace the former Sea King ASaC7 fleet which retired in September 2018. Current plans will see Crowsnest achieve initial operating capability in September 2021. Full operating capability is expected in May 2023.The original six year capability-gap between the retirement of the Sea King ASaC7 fleet and the entry service of Crowsnest was the source of much criticism. A PAC report had revealed the Main Gate decision for the Crowsnest to be around 2017. Crowsnest is now scheduled to be initially operational by late 2021. As a result of the time gap between the planned out of service date of the Sea King, and the introduction of "Crowsnest", seven Sea King ASaC.7 helicopters were extended in service until September 2018. Thales was selected as the chosen bidder to provide the radar and mission system at the heart of the Crowsnest capability on 22 May 2015. They will provide a slightly upgraded version of the existing Searchwater 2000 radar. All 30 of the Royal Navy's HM2 Merlins will be equipped to carry the Crowsnest system, though a maximum of 10 could be fitted with it at any one time. The RN has been slower to adopt unmanned systems than some other navies; following trials with the rail-launched ScanEagles it started operational flights of leased ScanEagles in January 2014 watching for swarm attacks on HMS Somerset and RFA Cardigan Bay in the Persian Gulf. This was expanded in November 2014, when 700X NAS was formed to serve as both the parent unit for ship based ScanEagle flights, and as the evaluation unit for any future RPAS systems that the Royal Navy elects to try. The ScanEagle will be withdrawn by 2017 and likely to be replaced by an unknown UAS, chosen through the Unmanned Warrior exercise in 2016. Dstl are testing ISR packages compatible with the RQ-20A Puma hand-launched UAV on board the M80 Stiletto US special forces trials ship in November 2014 under Capability Demonstration 15-1. The optionally-manned PZL-Świdnik SW-4 Solo completed trials with the RN in 2015 as part of the UK's RWUAS (Rotary Wing Unmanned Air System) Capability Concept Demonstrator (CCD) programme.