The United Kingdom bought three KC-135R aircraft for conversion to RC-135W Rivet Joint standard under the Airseeker project. Acquisition of the three aircraft was budgeted at £634m, with entry into service planned for October 2014.The aircraft formed No. 51 Squadron RAF, based at RAF Waddington along with the RAF's other ISTAR assets. They are expected to remain in British service until 2045.
Previously, the Royal Air Force had gathered signals intelligence with three Nimrod R1,converted in the 1970s from the Nimrod MR1 maritime patrol aircraft. When the time came to upgrade the maritime Nimrods to MRA4 standard, Project Helix was launched in August 2003 to study options for extending the life of the R1 out to 2025. The option of switching to Rivet Joint was added to Helix in 2008 and the retirement of the R1 became inevitable when the MRA4 was cancelled under the UK's 2010 budget cuts. The R1's involvement over Libya in Operation Ellamy delayed its retirement until June 2011.
Helix became Project Airseeker, under which three KC-135R airframes are being converted to RC-135W standard by L-3 Communications. L-3 will also provide ongoing maintenance and upgrades under a long-term agreement. The three airframes are former United States Air Force KC-135R, all of which first flew in 1964 but will be modified to the latest RC-135W standard before delivery. The three RAF airframes are the youngest KC-135s in the USAF fleet. As of September 2010 the aircraft had approximately 23,200 flying hours, 22,200 hours and 23,200 hours.
51 Sqn personnel began training at Offutt in January 2011 for conversion to the RC-135. The first RC135W (ZZ664) was delivered ahead of schedule to the Royal Air Force on 12 November 2013, for final approval and testing by the Defence Support and Equipment team prior to its release to service from the UK MAA.
1. ZZ664 Delivered 12th November 2013.
2. ZZ665 Delivered 3rd September 2015.
3. ZZ666 Delivered 8th June 2017.
Crew: 27: 3 pilots, 2 navigators, 22 rear-crew members
Length: 136 ft 3 in (41.53 m)
Wingspan: 130 ft 10 in (39.88 m)
Height: 41 ft 8 in (12.70 m)
Wing area: 2,433 ft² (226 m²)
Empty weight: 175,000 lb (V/W models) (79,545 kg)
Loaded weight: 297,000 lb (135,000 kg)
Max. takeoff weight: 322,500 lb (146,000 kg)
Powerplant: 4 × CFM International F-108-CF-201 turbofan engines, 22,000 lbf (96 kN) each
Maximum speed: 580 mph (933 km/h)
Range: 3,450 mi (5,550 km)
Service ceiling: 50,000 ft (15,200 m)
Rate of climb: 4,900 ft/min (1,490 m/min)