Although the airframe of the Nimrod R1 is essentially the same as the Nimrod MR1 ASW variant, internally the aircraft are completely different, apart from the flight deck area. Because of the sensitivity of the equipment involved, the aircraft were delivered as essentially empty shells to RAF Wyton where they were fitted out. The flight deck area consists of 5 crew (2 pilots, 2 navigators and a flight engineer) but additional space is available for 2 supplementary crew to provide relief on long sorties. Accurate navigation is essential and the aircraft were fitted out with AD360 ADF, AD260 VOR/ILS, AN/ARN-172 TACAN, AN/ARA-50 UFH DF, LORAN, and a Kollsman periscope sextant. The ASV-21D radar from the ASW variant was retained with a 32in diameter dish, but provision was made for an antenna up to 5ft. Up to 23 SIGINT specialists are accommodated at 13 side facing equipment consoles in the fuselage; console 1-5 are located on the port side with consoles 6-13 on the starboard side. Each console was designed to accommodate two 4ft modules with provision for a single seat placed centrally but able to slide on transverse rails. Consoles 1-4 and 9-12 had provision for a pair of side-by-side seats. Three forward facing single-man consoles now augment these double consoles.

The first Nimrod R1, XW664, was delivered to Wyton on 7 Jul 71 and took over 2 years to fit out. The first training sortie (Captained by Flt Lt Gordon Lambert) was flown on 21 Oct 73. The first operational sortie was flown on 3 May 74 and the type was formally commissioned into RAF service on 10 May 74. Two more Nimrod R1’s entered service during late 1974, XW665 and XW666, allowing the retirement of the last Comets and Canberra’s. For pilot training 51 Sqn also received a standard Nimrod MR1 (XZ283) on 8 Apr 76; this airframe stayed with the squadron until June ’78 when it was returned to BAe for conversion to AEW3 standard. Another Nimrod MR1 (XV252) then briefly acted as the trainer until the squadron reverted to the 3 operational aircraft.

In 1980 the aircraft were upgraded by replacing the ASV21 ASW radar with an ECKO 290 weather radar displaying in the cockpit this allowed the radar navigator crew position to be removed. The workload of the single navigator was improved by removing one of the LORAN sets and replacing it with a Delco AN/ASN-119 Carousel IVA INS. As a result of this upgrade one of the LORAN external aerials was removed and a variety of other external antennae appeared, believed to be used for direction finding. Wingtip pods, similar in appearance to the Yellow Gate Electronic Support Measures (ESM) fitted to the Nimrod MR2 also appeared on XW664 and then the other 2 aircraft. The requirement for in-flight refuelling became apparent as a result of Operation Corporate, the plan to recapture the Falkland Islands following the Argentinean invasion in 1982; however, the probes were not actually fitted until after the conflict was resolved. Along with the refuelling probe each aircraft also gained a large ventral fin, overwing vortex generators and retangular tailplane finlets. Underwing pylons were also fitted at the same time and these now carry a modified BOZ pod believed to contain a towed radar decoys. It is believed the aircraft is now also fitted with a Marconi Master satellite communications system.

The Nimrod R1 used during Op Corporate was XW664, where the aircraft operated from during the conflict in open to speculation, but some sources believe the aircraft operated from a base in Chile alongside a detachment of RAF Canberra PR9’s. In 1995 51 Sqn finally left RAF Wyton after 32 years in residence and moved to RAF Waddington from where it continues to operate.

Nimrod R1 XW666 was jokingly referred to by some personnel on 51 Sqn as ‘The Beast’ or ‘Damian’, because of the ‘satanic’ connotations of the number 666. Unfortunately, on 16 May 95, during an air-test, following a lengthy stay at the Nimrod Major Servicing Unit at Kinloss, a starter motor blew itself to bits and the debris punctured the wing and fuel tanks. A catastrophic fire broke out which was so severe that there was every likelihood the main spar holding the wing onto the fuselage would burn through and fail. The pilot of the aircraft, Flt Lt Art Stacey, had no choice but to carry out an immediate ditching in the Moray Firth from which all the crew survived. The aircraft was later recovered and scrapped. A Nimrod MR2, XV249, was identified as a suitable replacement and after a major overhaul at Kinloss the aircraft was ferried to BAe Woodford and stripped of all ASW equipment. After the installation of some antenna fairings, the aircraft was ferried to RAF Waddington on 19 Dec 96.

When XW666 was lost the 3 Nimrod R1’s were in the middle of a major modification programme known as Starwindow. The project had been launched to equip the R1’s with a new Open Systems architecture digital SIGINT suite, probably based on those carried by the RC-135 Rivet Joint aircraft operated by the USAF. The Starwindow system incorporates two high-speed search receivers, a wide band digital direction finding system and 22 pooled digital intercept receivers. New workstations were fitted for the ‘specialists’ in the rear of the aircraft. The Starwindow installation on XV249 began on 27 Dec 96 and the aircraft eventually flew as a fully equipped R1 on 11 Apr 97. In addition to the Starwindow package the R1’s were also fitted with a new ‘Special Signals’ intercept facility with a digital recording and playback suite, an enhanced pulse-signal processing capability and multi channel digital data demodulator.

On 21 Sep 05 it was announced that the RAF had completed flight trials and acceptance testing of a new airborne reconnaissance system named Extract that was designed specifically for the three Nimrod R1 SIGINT aircraft.

Developed by Raytheon Intelligence and Information Systems, Extract examines routine radio and radar emissions whilst providing electronic combat support to military commanders and will provide enhanced automated capabilities enabling it to respond to current and future threats. In addition to the Extract system on the Nimrod R1s, the company also supplied ground-based analysis systems and a rear crew trainer, as well as providing continued contractor logistic support for Extract through to 2013.

In addition to the new Extract system, Northrop Grumman have been selected to execute a £2 million first stage assessment phase for Project Helix, a program to provide a new mission suite, associated ground stations and training facilities to enhance the overall reconnaissance mission capabilities of the Nimrod R1. Also in competition for the final £200 million project are L-3 Communications’ Integrated Systems and Lockheed Martin’s Integrated Systems and Solutions, both of whom have also been awarded Phase 1 assessment contracts. In 2007 L-3 Communications Integrated Systems (L-3 IS) won a £11.5M contract to carry out the risk reduction studies for Helix Assessment Phase Stage 3. Main Gate approval is expected in June 2009 and L-3 IS will be the prefered contractor to execute the Project Helix Demonstration and Manufacture contract, with a projected value of £400M over a seven year period. The first upgraded aircraft is scheduled to be delivered in early 2013. The Nimrod R1s were planned to remain in service until 2012 and many expected these original aircraft to be replaced by a new version based on the Nimrod MRA4, however, this now appears unlikly to happen and a study will eventually determine how best to replace the capability provided by these three unique aircraft.