BAe Nimrod

BAe Nimrod MR.2 - XV260

The Nimrod was developed to meet an RAF requirement for a replacement for the ageing Avro Shackleton. In 1964 two unsold Comet 4 airliners were selected as prototype airframes for the new maritime patrol aircraft. These two prototypes were given the Hawker Siddeley model number 801, and the first flew in converted form on May 23rd 1967. Changes to the Comet included the replacement of the airliner’s RR Avon turbojets with Spey turbofans (increasing fuel efficiency, and thus range - the Nimrod can cruise while on patrol on 2 of its 4 Spey's) and the new lower fuselage with an internal weapons bay and extended nose to contain a search radar. Other changes included a Magnetic Anomaly Detector (MAD) mounted in a boom extending from the rear fuselage, and ESM sensors mounted in a fairing on top of the tail. The first of 46 Nimrod MR.1's ordered entered RAF service in October 1969.

The MR.2 designations applies to an upgrade applied to 32 Nimrod's from 1975. The upgrade involved a new central tactical system with a new computer and processors, new communications suite and EMI’s Searchwater radar. Subsequently the fleet was modified to MR.2P standard with the addition of an in-flight refuelling probe, and more recently Nimrod's have been fitted with Loral wingtip ESM pods. A mid 1980s program to adapt the Nimrod as an AEW aircraft, (designated AEW.3) was cancelled due to technical problems. Two further Nimrod's (a third made a successful ditching off the coast of Scotland in May 1995) serve as R.1P Elint platforms. Identifiable by the lack of MAD boom, the R.2's are still officially identified as radar calibration aircraft, but are fitted with sensors to detect and record electronic emissions.

In 1992 the RAF started a Replacement Maritime Patrol Aircraft (RMPA) procurement program to replace the Nimrod MR.2 aircraft. To meet the requirement BAe proposed rebuilding each Nimrod MR.2 with new engines and electronics which it called Nimrod 2000. The RAF considered bids from Lockheed and Dassault but in December 1996 awarded the contract to BAe for the Nimrod 2000 as the Nimrod MRA.4. The MRA.4 is essentially a new aircraft, with current-generation Rolls-Royce 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. Development has taken longer than anticipated and the first of 12 MRA.4's have only just entered service. The contract was initially for the supply of 21 rebuilt Nimrod's, but due to technical problems the project was halted. Early in the contract BAe discovered that none of the Nimrod airframes supplied by the RAF for refurbishing were to a common standard. This considerably complicated the refurbishment process.

On July 30th, 2007, the Nimrod MRA.4 successfully released the Sting Ray torpedo for the first time. The safe separation trial to demonstrate the ability to deploy this store from the MRA.4 bomb bay took place at Aberporth range off the coast of West Wales. The MRA.4 was expected to enter RAF service in 2010, but the program was cancelled due to defence cuts and all Nimrod's were retired and scrapped by the end of 2011.

The Nimrod is used in four main roles: Anti Submarine Warfare (ASW), Anti-Surface-Unit Warfare (ASUW), Intelligence and Communications Support and Search and Rescue (SAR). The operating crew comprises two pilots and a flight engineer, two weapon systems officers (WSO) (tactical and routine), and a WSO who is the sensor and communications coordinator. He is, in turn, supported by a team of two 'wet' weapon systems operators (WSOps) and four 'dry' WSOps. The 'wet' team supervise the aircraft’s acoustic processors, which monitor active and passive sonobuoys, whilst the 'dry' team manage a range of radar and non-acoustic sensors, all of which are essential to delivering Nimrod’s full capability. The aircraft can carry in excess of 200 sonobuoys internally, of several different types, both active and passive, which are delivered via two unpressurised 6-buoy rotary launchers and two pressurised singleshot launchers. The Nimrod’s offensive weapons include Sting Ray torpedoes for use in the ASW and ASUW role and for self-defence the aircraft is fitted with Defensive Aids systems and may be armed with four wing-mounted Sidewinder air-to-air missiles. For SAR purposes the aircraft has a selection of air deliverable, multi-seat dinghies and survival packs.

The majority of the Nimrod’s tasking comes from the UK Maritime Air Operations Centre at the Joint Northwood HQ. Peacetime work includes worldwide surface and sub-surface surveillance and the maintenance of a permanent standby for UK and overseas operations or SAR in support of the Aeronautical Rescue Coordination Centre, collocated at RAF Kinloss. SAR tasks include long-range search and shepherd, assistance to SAR helicopters and coordination of search activities as the On-Scene Commander at major incidents. The aircraft routinely operates over the sea down to 200 ft, but is limited to 300 feet at night or in bad weather.

The Nimrod MR.2 has also provided a continual presence in the Middle East since late 2001. In that time, employment of the aircraft has evolved to take on an additional range of non-traditional tasks, including overland Electro-Optic IMINT (Image Intelligence) surveillance of Iraq and Afghanistan, and IMINT and communications support to coalition ground troops. The Nimrod MR.2 will continue in service until it is replaced by the MRA.4, which was expected to enter service around 2010.

However the project for the MRA.4 was subject to significant delays due to cost over-runs and contract re-negotiations. This was partly due to difficulties combining refurbished Nimrod MR.2 fuselages, which had not been built to a common standard, with newly built wings. The numbers of aircraft to be procured fell from 21 to nine over a course of years, while costs continued to climb. The MRA.4 was ultimately cancelled in late 2010 as a result of the Strategic Defence and Security Review, at which point it was £789 million over-budget and over nine years late.

The final flight of a Nimrod in RAF service took place on 28th June 2011, with XV249 given the honours and operated by No.51 Sqn.