British Aerospace Nimrod AEW3 The British Aerospace Nimrod AEW3 was a planned airborne early warning ( AEW ) aircraft intended as to provide airborne radar cover for the air defence of the United Kingdom by the Royal Air Force ( RAF ) . The project was designed to use the existing Nimrod airframe , in use with the RAF as a maritime patrol aircraft , combined with a brand new radar system and avionics package developed by Marconi Avionics . The Nimrod AEW project proved to be hugely complex and expensive for the British government , as a result of the difficulties of producing brand new radar and computer systems and integrating them successfully into the Nimrod airframe . Despite close to a decade ' s work , the project was eventually cancelled , with the RAF instead purchasing new build Boeing E - 3 Sentry aircraft to fulfil the AEW requirement . Development . Background . In the mid 1960s following the development of the Grumman E - 2 Hawkeye carrier - borne AEW aircraft and its associated systems , the British government began looking around for a radar system that could be used to provide airborne early warning for the United Kingdom . At the time , the only recognised AEW aircraft in British service was the Fairey Gannet aircraft used by the Fleet Air Arm on board Royal Navy aircraft carriers . These were fitted with the AN / APS - 20 Radar , which had been developed during World War II and was rapidly becoming obsolete . Work had been started in the early 1960s on a brand new AEW platform for the Royal Navy to replace the Gannet that would encompass both a new type of radar system mounted on a new aircraft , the P . 139 . While the defence cuts of the mid 1960s led to the cancellation of the P . 139 , work continued on a wholly British designed radar system , while strategic thinking led to a decision being taken that the RAF needed an AEW aircraft to operate as part of the national air defence strategy . To fulfill the planned requirements for a new land based AEW aircraft , the government had a number of factors to consider : Designers at Hawker Siddeley Aviation came up with a proposal that would see the FMICW radar system installed using a Fore Aft Scanner System in the new Nimrod aircraft . This proposal was rejected as being too expensive , with instead a proposal to convert surplus Andover transport aircraft . This though was also rejected due to the potential cost of development . In the interim , to provide a land based AEW aircraft , radar systems from withdrawn Royal Navy Gannets were installed in similarly surplus Avro Shackleton maritime patrol aircraft and commissioned into service from 1972 . At around the same time , it was decided not to proceed with FMICW technology as the basis of an AEW system , as research from the US Air Force had shown that pulse - doppler radar was superior and would be used in the brand new aircraft then under development . As a consequence , the idea of a new land - based AEW aircraft for the RAF was re - examined , and again it was decided that the Nimrod met the requirements . The decision was taken to procure the aircraft fitted with a pulse - doppler radar system , which then proceeded to a range of options : While the fourth option was the most attractive as far as British industry was concerned , in that it would sustain thousands of British jobs , it was also far riskier than purchasing an " off the shelf " product or spreading the risk across multiple partners . In 1977 , the US had made an offer to NATO for purchasing several of the new Boeing E - 3 Sentry aircraft , which were being delivered to the US Air Force ; this was intended to provide airborne early warning cover for Europe ' s NATO nations without having to rely on the United States , and eventually came into being as the NATO E - 3A Component . However , the complex multi - lateral negotiations eventually led the United Kingdom to pursue the all - British development . Development issues . In 1977 an RAF Comet 4 was modified for flight testing with the nose radome and conducted a series of trials , the results of which proved promising enough for an order for three prototype Nimrods to be built using redundant MR1 airframes . The first of these was rolled out in March 1980 and flew for the first time in July , and was intended to test the flight characteristics , with the second airframe planned to carry out trials on the " Mission Systems Avionics " ( MSA ) package . The MSA was based around a GEC 4080M computer , which was required to process data from the two radar scanners , the ESM system , IFF and inertial navigation systems . The integration of all of these systems into a single package proved too difficult for the underpowered computer , which had an ultimate data storage capacity of 2 . 4 MB . Additionally , when operating at full power the radar scanners and on - board electronic systems generated a significant amount of heat . A system was developed to channel this via the fuel system , from where it could then dissipate , but which only worked when the fuel tanks were at least half full . Cancellation . Despite the problems , the Nimrod was persevered with , and 8 production aircraft were ordered ( which would also come from spare MR1 airframes ) , with the first of these flying in March 1982 . Even while the technical problems were being worked on , the aircraft was delivered to the RAF , with No 8 Squadron , the RAF ' s AEW squadron which at that time operated the Shackleton , receiving its first in 1984 to begin crew training . The problem was that , with an anticipated in - service date of mid 1982 , No 8 Squadron had been reduced from 12 aircraft and crews to 6 as part of the 1981 Defence Review . By the time of the Falklands War , the Nimrod AEW had been originally scheduled to be in service ; however the technical problems proved insurmountable to be deployed in the conflict . To provide some degree of cover , several Nimrod MR . 2 were quickly modified to undertake the airborne surveillance role for the task force however . However , at the same time , the MoD decided to conduct a complete review of the AEW programme . The result of this was the start of a bid process to supply AEW aircraft for the RAF that began in 1986 . The primary bidders were GEC Marconi with the Nimrod , and Boeing with its Sentry . In December 1986 , the Sentry was finally chosen and the Nimrod AEW programme was cancelled . In spite of the project ' s difficulties however , India expressed interest in procuring the Nimrod AEW3 ; these investigations continued even after the British government ' s eventual cancellation of the project . The Nimrod programme had cost in the region of £1 billion up to its cancellation , contrasting with manufacturer claims in 1977 that the total cost of the project would be between £200 - 300 million . The unused airframes were eventually stored and used as a source of spares for the Nimrod R1 and MR2 fleets , while the elderly Shackleton aircraft that had been commissioned in 1971 as a " stop - gap " measure for AEW cover until the planned entry of the Nimrod were forced to soldier on until 1991 and the entry into RAF service of the Sentry . The scandal over the collapse of the Nimrod AEW project was a major factor in Prime Minister Margaret Thatcher ' s stance to open up the UK defence market to competition . Potential future use . Following the cancellation of the Nimrod AEW programme , BAe Woodford began looking at ways that the now redundant airframes could be re - used , and entered into studies looking at the potential use of the Nimrod as a missile carrying strike aircraft . BAe ' s intention would have seen the AEW modifications , primarily the FASS scanners , and the fuel and cooling systems installed in the weapons bay , removed . The Searchwater radar , at the time fitted to the Nimrod MR . 2 , would have been installed in a nose installation , and the weapons bay outfitted to accommodate up to six Sea Eagle anti - ship missile s . However , this did not go beyond the study phase , and the airframes were eventually scrapped during the 1990s . Issues . The thinking behind the attempted development of the Nimrod AEW was to maintain Britain ' s position at the forefront of radar technology and development as part of defence . However , the complexity of the AEW requirement proved too much for British industry to overcome by itself . A major project management issue was the appointment of British Aerospace and GEC Marconi as joint programme leaders . This meant in practice that as development issues arose , the companies had a distressing tendency to blame each other for the problem rather than try to resolve it . The choice of the Nimrod airframe proved to be the wrong one , as it was too small to accommodate the radar , electronics , power generation and cooling systems needed for a system as complex as the one required – at just over , the Nimrod was close to shorter than the Boeing 707 aircraft that formed the basis of the E - 3 Sentry , but was expected to accommodate sufficient crew and equipment to perform a similar function . The choice of computer to integrate the various sensor systems was wrong , as the GEC 4080M was simply too slow and too underpowered to perform the tasks required of it : by the time of project cancellation , the mission system mean time between failure was around 2 hours , yet it took around 2 and a half hours to load all the mission data via a tape system . What mission performance there was largely due to the Cossor IFF interrogator which complemented the radar system : with the addition of IFF data , the system could successfully track aircraft carrying IFF transponders , but when the IFF was switched off , radar tracks would rapidly be lost . This meant that the system would successfully track civil and ' friendly ' military aircraft , but would not reliably detect Warsaw Pact aircraft which did not carry a compatible IFF system - detection of which was the whole point of the project . The mission system electronic racks were earthed to different points on the airframe , which led to differences in earth potential and the introduction of short - lived , random track information which added to the computer overload . Finally , the advanced design of the radar proved difficult - the FASS method to gain full 360° radar coverage was problematic , involving as it did the scanner in the nose making a left to right sweep , with the signal then immediately passed to the scanner in the tail , which would sweep right to left . However , getting the two scanners to synchronise proved difficult , resulting in poor all - round surveillance capability . The system also split incoming raw radar information into upper and lower beams , each of which was then further split into in - phase and quadrature - phase channels . Each of these 4 channels contained identical individual elements ( such as a spectrum analyser ) , which in theory should have been entirely interchangeable between locations . JTU trials showed that in fact the system would only work with a particular device in a particular place in the system : putting the same device in one of the other 3 channels would not give a serviceable system . The consequence of this was that the JTU trials aircraft would fly loaded with spare electronic devices so that when system failure occurred , there was a better chance of finding a particular combination of system elements which would work . This would not have been a sustainable practice had the aircraft entered service . The reason for this issue was never resolved : the JTU suspicion was that tolerances in transmitting information through each channel were too loose , so that as the processed information emerged from each channel to be correlated back into a coherent picture , such correlation was in fact impossible since each channel was offering up a different ' time slot ' to the others .