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The Nimrod has been the Royal Air Force's primary maritime patrol bomber since replacing the Avro Shackleton in the early 1970s. It is a conversion of the De Havilland Comet, the world's first jet airliner. It was originally designed by Hawker-Siddeley, but today BAE Systems is the prime contractor. The Nimrod serves the RAF in two variants: the R1 variant in a reconnaissance and electronic intelligence gathering capacity (ELINT), and the MR2 variant in the Maritime Reconnaissance role.
The Nimrod was the first jet-powered patrol aircraft to be designed; earlier designs generally used piston or turboprop engines to improve fuel economy and allow for long duration patrols. Jet engines are generally very "thirsty" at low altitudes, but the Nimrod's huge fuel capacity made up for this. It can also shut down two outboard engines at low altitude to extend endurance. When needed, the Nimrod could "dash" to its targets at a speed that no propeller aircraft could match. Since the introduction of the Nimrod, most new patrol designs have been jet powered, including the US Navy's S-3 Viking and future P-8.
Development
MR1
Nimrod development began in 1964 as a project to replace the elderly Avro Shackleton. Like many other successful maritime patrol aircraft, it was based on a civil airliner which had reached the end of its market life - in this case, the Comet 4. The first two RAF aircraft were unfinished Comet 4 airliners. The Comet's turbojet engines were replaced with Rolls-Royce Spey turbofans (for better fuel efficiency, particularly at the low altitudes required for maritime patrol), and major changes made to the fuselage, including an internal weapons bay, an extended nose for radar, a new tail with ESM sensors mounted in a bulky fairing, and a MAD boom. After a first flight in May 1967 the RAF ordered 46 Nimrod MR1s, and the first example entered service in October 1969. Five squadrons were eventually equipped with the MR1.R1
Three Nimrod aircraft were adapted to the SIGINT role, replacing the Comet C2s and Canberras of No. 51 Squadron in May 1974. The R1 is distinguished from the MR2 by the lack of a MAD boom. Only since the end of the Cold War has the role of the aircraft been officially acknowledged. Officially these were once described as "radar calibration aircraft". The R1s have not suffered the same rate of fatigue and corrosion of the MR2s and will continue in service long after the MR2 is replaced by the MRA4. New Bombardier Sentinel R1 (ASTOR) aircraft due for delivery from mid 2004 may take on some duties performed by the R1.The Nimrod R1 is based at RAF Waddington in Lincolnshire, England and flown by 51 Sqn.
MR2
Starting in 1975, 32 aircraft were upgraded to MR2 standard, involving modernisation of the electronic suite and (as the MR2P) provision for inflight refueling and additional ESM pods on the wingtips. The inflight refueling capability was introduced during the Falklands War, as well as hardpoints to allow the Nimrod to carry the AIM-9 Sidewinder missile (giving rise to the aircraft being called "the largest fighter in the world"). Eventually all MR2s gained refueling probes and the "P" designation was dropped. The Nimrod MR2 carries out three main roles; Anti-Submarine Warfare (ASW), Anti-Surface Unit Warfare (ASUW) and Search and Rescue (SAR). Its extended range enables the crew to monitor maritime areas far to the north of Iceland and up to 4,000 km out into the Western Atlantic. With AAR (Air-to-Air Refuelling), its range and endurance is greatly extended. The MR2 is a very lethal submarine killer carrying the most up to date sensors and data processing equipment linked to the weapon systems. In addition to weapons and sonar-buoys, a searchlight can be mounted in the starboard wing pod for search and rescue (SAR) operations.Crew members comprise 2 x Pilots and 1 x Flight Engineer operate the flight deck, 2 x Navigators (1 x Tactical Navigator and 1 x Routine Navigator), 1 x Air Electronics Officer (AEO), the sonobuoy sensor team of 2 x Weapon System Operators WSOp (ACO) and 4 x Weapon System Operators WSOp (EW) to manage passive and active electronic warfare systems. Two of the WSOps will be tasked as observers positioned at the Port and STBD Beam lookout windows when transiting or flying in dense air traffic. The MR2 has the longest Bomb Bay of any NATO aircraft.
The Nimrod MR2 is based at RAF Kinloss in Scotland and flown by 201, 120 and 42(R) Sqns.
First maintenance of the MR2 is carried out by the Nimrod Line Sqn.
Software Support for the MR2 is carried out by the Nimrod Software Team also based at RAF Kinloss
AEW3
In the mid-1970s, the Nimrod's duties were expanded to include AEW - again, as a replacement for the Lancaster-derived, piston-engined Shackleton which, astonishingly, was still in service in that role. The aircraft were modified by BAe at the former Avro plant at Woodford, Manchester to house the GEC Marconi radars in a bulbous nose and tail (see picture). From the start of the first flight trials in 1982 the Nimrod AEW3 project was plagued by cost over-runs and electronic difficulties. Eventually, the UK MOD realised that the cost of developing the radar system to achieve the required level of performance was prohibitive and the probability of success very uncertain, and in December 1986 the project was cancelled. The RAF eventually received seven Boeing E-3 Sentrys (AWACS) instead, with proven radar performance and electronic enhancements to the original USAF systems to address UK-specific requirements. Of the eleven RAF aircraft that were selected for conversion to AEW3 standard, none returned to the maritime reconnaissiance role: all were eventually reduced for spares to support the maritime Nimrod fleet.MRA4
In 1992 the RAF started a Replacement Maritime Patrol Aircraft (RMPA) procurement programme to replace the Nimrod MR2 aircraft. To meet the requirement BAe proposed re-building each Nimrod MR2 with new engines and electronics which it called 'Nimrod 2000'. The RAF considered bids from Lockheed with its P-3 Orion, Loral Corp. with rebuilt ex-US Navy Orions, and Dassault with the Atlantique 3, but in December 1996 awarded the contract to BAe for the Nimrod 2000 which was then renamed the Nimrod MRA4.The MRA4 is essentially a new aircraft, with current-generation BMW Rolls-Royce (now known as Rolls-Royce Deutschland) BR710 turbofan engines, a new, larger wing, and fully refurbished fuselage. Much larger air intakes are required, because the airflow of the BR710 engine is significantly higher than that of the original Spey 250/251. The rebuilt aircraft borrow heavily from Airbus technology, the wings are designed and manufactured by BAE Systems (the UK Airbus partner) and the glass cockpit is derived from that of the Airbus A340.
Development has taken longer than anticipated, but the first of 18 MRA4s are expected to enter service shortly. The contract was initially for the supply of 21 rebuilt Nimrods, but due to technical problems the project was brought to a halt. Early in the contract, BAeS discovered that none of the Nimrod airframes supplied by the RAF for refurbishing were to a common standard, which considerably complicated the refurbishment process.
Following public recriminations between the Ministry of Defence and BAE the contract was renegotiated, for the revised number of 18 aircraft. Officially this is put down to the fact that increased capability and availability of the MRA4 will require fewer aircraft, but it has been suggested that this is in effect compensation to BAE, who had to absorb the cost increases of the project. Announcing plans for the future of the British military on July 21 2004 Defence Secretary Geoff Hoon detailed plans to reduce the upgrade programme to cover only 16 aircraft and suggested that an eventual fleet of twelve may suffice.
BAE Systems offered a new build version of the Nimrod for the US Navy's Multimission Maritime Aircraft (MMA) competition. The competition was launched in 2000; BAE withdrew in October 2002, recognising the political reality that the failure to find a US-based production partner made the bid unrealistic. Boeing's 737 won the competition on June 14, 2004.
The first flight of a Nimrod MRA4 (the aircraft designated PA1) occurred on Thursday 26 August 2004. As of June of 2006, the Nimrod MRA4 program was 87 months(7 years, three months) behind schedule and £1,000 million over budget.
Specifications (MR2/R1)
Specifications (MRA4)
Units Using the Nimrod
Royal Air Force
- No. 42(R) Squadron - Nimrod OCU (MR2)
- No. 51 Squadron - R1
- No. 120 Squadron - MR2
- No. 201 Squadron - MR2
Related content
British ASW aircraft 1960-1969 | British patrol aircraft 1960-1969 | United Kingdom defence procurement
"Hawker-Siddeley Nimrod"