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Hawker Siddeley Nimrod


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The Hawker Siddeley Nimrod is a military aircraft developed and built in the United Kingdom. It is an extensive modification of the de Havilland Comet, the world's first jet airliner. It was originally designed by de Havilland 's successor, Hawker Siddeley, now part of BAE Systems.

It was designed as a Royal Air Force maritime patrol aircraft, the Nimrod MR1/MR2, with the major role being anti-submarine warfare (ASW), although it also had secondary roles in maritime surveillance and anti-surface warfare. It served in this role from the early 1970s until March 2010. The current Nimrod series was due to be replaced by the now cancelled Nimrod MRA4.

The RAF also uses the Nimrod R1 variant in an electronic intelligence gathering (ELINT ) role.

Development

Five separate marks of the Nimrod have been developed during the period of the type's service with the RAF. Of these, three have been successfully in service;

*MR1 - the initial maritime reconnaissance variant

*MR2 - an upgraded version of the MR1

*R1 - a Mark 1 Nimrod optimised for the signals intelligence role

The other two were unsuccessful and were eventually cancelled before they could enter front-line service;

*AEW3 - an airborne early warning version cancelled in 1986 in favour of the E-3 Sentry

*MRA4 - an upgraded version of the MR2 cancelled in 2010 in a defence review

MR1

The development of the Nimrod patrol aircraft began in 1964 as a project to replace the Avro Shackleton. The Nimrod design was based on that of the Comet 4 civil airliner which had reached the end of its market life (the first two RAF aircraft were unfinished Comets). The Comet's turbojet engines were then replaced with Rolls-Royce Spey turbofan s for better fuel efficiency, particularly at the low altitudes required for maritime patrol. Major fuselage changes were made, including an internal weapons bay, an extended nose for radar, a new tail with electronic warfare (ESM) sensors mounted in a bulky fairing, and a MAD (Magnetic anomaly detector ) boom. After the first flight in May 1967, the RAF ordered 46 Nimrod MR1s. The first example (XV230 ) entered service in October 1969. Five squadrons were eventually equipped with the MR1.

R1

Three Nimrod aircraft were adapted for the signals intelligence 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; they were once described as "radar calibration aircraft". The R1s have not suffered the same rate of fatigue and corrosion of the MR2s. One R1 was lost in a flying accident since the type's introduction; this occurred in May 1995 during a flight test after major servicing, at RAF Kinloss. To replace this aircraft an MR2 was selected for extensive conversion, undertaken by BAE Systems at the Woodford factory, to R1 standard, and entered service in December 1996.

The Nimrod R1 is based at RAF Waddington in Lincolnshire, England and flown by 51 Sqn. The two remaining Nimrod R1s were originally planned to be retired at the end of March 2011, but operational requirements forced the RAF to deploy one to RAF Akrotiri, Cyprus on 16 March in support of Operation Ellamy. They will now be kept in service for at least another 3 months until June 2011. The R1 will be replaced by ex-USAF Boeing RC-135W ''Rivet Joint'' aircraft starting in 2014, known as Air Seeker.

MR2

Starting in 1975, 32 aircraft were upgraded to MR2 standard, including modernisation of the electronic suite and (as the MR2P) provision for in-flight refuelling and additional ESM pods on the wingtips. The in-flight refuelling capability was introduced during the Falklands War, as well as hardpoints to allow the Nimrod to carry the AIM-9 Sidewinder missile for use against Argentine Air Force Boeing 707 which were configured for maritime patrol/surveillance duties shadowing the British naval task force. Eventually all MR2s gained refuelling probes and the "P" designation was dropped.

The Nimrod MR2 carried out three main roles - Anti-Submarine Warfare (ASW), Anti-Surface Unit Warfare (ASUW) and Search and Rescue (SAR). Its extended range enabled the crew to monitor maritime areas far to the north of Iceland and up to 4,000 km out into the Western Atlantic. With Air-to-Air Refuelling (AAR), range and endurance was greatly extended. The MR2 was a submarine killer carrying up to date sensors and data processing equipment linked to the weapon systems. In addition to weapons and sonobuoy s, a searchlight was mounted in the starboard wing pod for Search and Rescue (SAR) operations.

The crew consisted of two pilots and one flight engineer, two navigators (one tactical navigator and a routine navigator), one Air Electronics Officer (AEO), the sonobuoy sensor team of two Weapon System Operators (WSOp ACO) and four Weapon System Operators (WSOp EW) to manage passive and active electronic warfare systems. Two of the WSOps were used as observers positioned at the port and starboard beam lookout windows when flying in dense air traffic. The MR2 had the longest bomb bay of any NATO aircraft.

The Nimrod MR2 was based at RAF Kinloss in Scotland and flown by 201, 120 and 42(R) Squadrons. First maintenance of the MR2 was carried out by the Nimrod Line Sqn. Software support for the MR2 was carried out by the Nimrod Software Team also based at RAF Kinloss. The Nimrod MR2 aircraft was withdrawn on 31 March 2010, a year earlier than planned, for financial reasons. The last official flight of the MR2 Nimrod took place on 26 May 2010, with XV229 flying from RAF Kinloss to Kent International Airport, Manston in Kent, where it will be used by the nearby MOD Defence Fire Training and Development Centre as an evacuation training airframe.

AEW3

In the mid-1970s a modified Nimrod was proposed for the Airborne Early Warning (AEW) mission — again as a replacement for the Lancaster -derived, piston-engined Shackleton AEW.2. Eleven existing Nimrod airframes were to be converted by British Aerospace at the former Avro plant at Woodford to house the GEC Marconi radars in a bulbous nose and tail. The Nimrod AEW3 project was plagued by cost over-runs and problems with the GEC 4080M computer used. Eventually, the MoD recognised 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 Sentry aircraft instead.

MRA4

The Nimrod MRA4 was intended to replace the capability provided by the MR2. It was essentially a new aircraft, with current-generation Rolls-Royce BR710 turbofan engines, a new larger wing, and fully refurbished fuselage. However the project was subject to delays, cost over-runs, and contract re-negotiations. It was cancelled in 2010 as a result of the Strategic Defence and Security Review at which point it was £789 million over-budget and nine years late. The prototype aircraft, produced at a cost of over £1bn each, have been scrapped.

Design

The Nimrod is the first jet-powered Maritime Patrol Aircraft (MPA). Earlier MPA designs used piston engine s or turboprop engines to improve fuel economy and to allow for lengthy patrols at low altitudes, as with the Lockheed P-3 Orion. Jet engines are most economical at high altitudes and less economical at low altitudes; the aircraft can travel to the operational area at high altitude which is economical on fuel and fast compared to earlier piston aircraft. On reaching the patrol area the Nimrod descends to its working altitude.

On patrol at high weight all four engines are used, but as fuel is consumed and weight is reduced first one and then a second engine is shut down, allowing the remaining engines to be run at an efficient RPM rather than running all engines at less efficient RPM. A "rapid start" system is fitted should the closed-down engines need to be restarted quickly; instead of relying only on ram air for restarting an engine, compressor air from a live engine is used in a starter turbine which rapidly accelerates the engine being started. All engines are used for travel back to base at high altitude.

Operational history

At first the crews, who were transferred to the Nimrod from the piston-engine Avro Shackleton s, were not enthusiastic with the craft, mainly because its sensor suite was only marginally superior to the Shackleton's. In fact most sensors were the same, although the aircraft had a new digital data fusion computer. The Nimrod gave sterling service during the "Cod Wars " between Iceland and the UK over fishing rights. During the Falklands war (Operation Corporate), several Nimrods combed the sea for enemy submarines. The Nimrods took part in Operation Granby (the Gulf War 1990/1991), the NATO operations against Serbia in 1999, Operation Telic (the Iraq war in 2003 and beyond), the campaign in Afghanistan, and over Libya in 2011. They also were a routine component of British search and rescue (SAR) operations in the North Sea.

Search and rescue

While the Nimrod MR1/MR2 was in service, one aircraft from each of the squadrons on rotation was available for search and rescue operations at one-hour standby. The standby aircraft carried two sets of Lindholme Gear in the weapons bay. Usually one other Nimrod airborne on a training mission would also carry a set of Lindholme Gear. As well as using the aircraft sensors to find aircraft or ships in trouble, it was used to find survivors in the water, with a capability to search areas of up to. The main role would normally be to act as on-scene rescue coordinator to control ships, fixed-wing aircraft, and helicopters in the search area.

Because of the search and rescue role, Nimrod aircraft often appeared in the media in connection with major rescue incidents. In August 1979 a number of Nimrods were involved in finding competitors in distress in the disaster-stricken 1979 Fastnet race, and directing helicopters to the scene. The ''Alexander L. Kielland'' was a Norwegian semi-submersible drilling rig that capsized whilst working in the Ekofisk oil field in March 1980 killing 123 people. Six different Nimrods searched for survivors and took it in turn to provide a rescue co-ordination role, involving the control of 80 surface ships and 20 British and Norwegian helicopters; control became particularly important as the visibility deteriorated. In an example of the search capabilities, in September 1977 when an attempted crossing of the North Atlantic in a Zodiac inflatable dinghy went wrong, a Nimrod found the collapsed dinghy and directed a ship to it.

Offshore Tapestry

Tapestry is a codeword for the activities by ships and aircraft that protect the United Kingdom's Sovereign Sea Areas, including the protection of fishing rights and oil and gas extraction. Following the establishment of a Exclusive Economic Zone (EEZ) at the beginning of 1977 the Nimrod fleet was tasked with patrolling the area. The aircraft would locate, identify, and photograph vessels operating in the EEZ. The whole area was normally covered every week, with each vessel being photographed. The aircraft would also check and communicate with all oil and gas platforms. In 1978 a Nimrod arrested an illegal fishing vessel from the air in the Western Approaches and made the vessel proceed to Milford Haven for further investigation. During the Icelandic Cod Wars of 1972 and 1975-1976 the Nimrod aircraft operated with Royal Navy surface vessels protecting British fishing fleets.

Operators

UK

*Royal Air Force

Aircraft on display

MR2 variants

*XV226 - Bruntingthorpe Aerodrome

*XV231 - Manchester Airport viewing park

*XV232 - Coventry airport

*XV240 - Gate guardian at RAF Kinloss

*XV250 - Yorkshire Air Museum

*XV254 - Highland Aviation Museum, Inverness Airport (Forward of fuselage preserved)

*XV255 - City of Norwich Aviation Museum

AEW3

*Cockpit at Solway air Museum, Carlisle

Accidents and incidents

Five Nimrods have been lost in accidents :

*On 17 November 1980, a Nimrod MR2 XV256 crashed near RAF Kinloss after three engines failed following multiple birdstrikes. Both pilots were killed but the remaining crew survived.

*On 3 June 1984, a Nimrod MR2 XV257 stationed at RAF St Mawgan suffered extensive damage when a reconnaissance flare ignited in the bomb bay during flight. The aircraft successfully returned to base but was subsequently written-off due to fire damage. There were no casualties.

*On 16 May 1995, XW666, a Nimrod R1 from RAF Waddington, ditched in the Moray Firth from Lossiemouth after an engine caught fire during a post-servicing test flight from RAF Kinloss. The Ministry of Defence (MoD) inquiry identified a number of technical issues as the cause. There were no casualties.

*On 2 September 1995, a Nimrod MR2 XV239 crashed into Lake Ontario while participating in the Canadian International Air Show, killing the seven crew members.

*On 2 September 2006, a Nimrod MR2 XV230 crashed near Kandahar in Afghanistan, killing 12 airmen, one marine and one soldier — the largest single day loss of UK personnel since the Falklands War. This was the first Nimrod to enter operational service, originally as a MR1 but upgraded to MR2 standard in the 1980s. On 23 February 2007, the Ministry of Defence grounded all MR2 aircraft while fuel pumps were inspected. The MoD stressed that this was not necessarily related to the crash in Afghanistan.

* On 5 November 2007, XV235 was involved in a midair incident over Afghanistan when the crew noticed a fuel leak during air-to-air refuelling. After transmitting a mayday call, the crew landed the aircraft successfully. The incident came only a month before the issue of the report of a Board of Enquiry into the 2 September 2006 fatal accident to XV230 in (likely) similar circumstances. The RAF subsequently suspended air-to-air refuelling operations for this type.

Specifications