Hawker Siddeley (now BAE Systems) Nimrod

Hawker Siddeley Nimrod
An RAF Nimrod MR2 taxis for takeoff
RoleMaritime patrol aircraft
ManufacturerHawker Siddeley
BAE Systems
First flightMay 1967
IntroducedOctober 1969
StatusActive
Primary userRoyal Air Force
Number built49 (+2 prototypes)
Developed fromde Havilland Comet

The Hawker Siddeley Nimrod is a maritime patrol aircraft developed 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. A major modification was the fit of a large weapon bay under the fuselage that can carry and drop torpedoes, mines, bombs and other stores. Sonobuoys for tracking submarines are dropped from special launchers in the rear of the fuselage.

The Nimrod is also capable of carrying American-made Harpoon anti-ship missiles, and Sidewinder air-to-air missiles for self-defense.

The Nimrod has been the Royal Air Force's primary Maritime Patrol Aircraft (MPA) since the early 1970s, when it replaced the piston-engined Avro Shackleton. The RAF uses two Nimrod variants: the MR2 variant in the Maritime and Reconnaissance role; the R1 variant in a reconnaissance and electronic intelligence gathering capacity (ELINT).

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 then replaced with Rolls-Royce Spey turbofans 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

Nimrod MR1 XV231 at NAS Norfolk (USA) in 1984. Hawker Siddeley (now BAE Systems) Nimrod R1

Three Nimrod aircraft were originally 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. 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. One R1 has been 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.

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 (giving rise to the aircraft being called "the largest fighter in the world"). Eventually all MR2s gained refuelling 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 Air-to-Air Refuelling (AAR), range and endurance is greatly extended. The MR2 is a submarine killer carrying up to date sensors and data processing equipment linked to the weapon systems. In addition to weapons and sonobuoys, a searchlight can be mounted in the starboard wing pod for Search and rescue (SAR) operations.

The crew consists of two pilots and one flight engineer, two navigators (one tactical navigator and a routine navigator), one Airborne Eating 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 will be used as observers positioned at the port and starboard beam lookout windows when 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) Squadrons. 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

Nimrod AEW3

In the mid-1970s the Nimrod's duties were expanded to include Airborne Early Warning and Control (AEW) again as a replacement for the Lancaster-derived, piston-engined Shackleton which was still in service in that role. The aircraft were modified by British Aerospace at the former Avro plant at Woodford, Greater Manchester to house the GEC Marconi radars in a bulbous nose and tail. From the start of the first flight trials in 1982 the Nimrod AEW3 project was plagued by cost over-runs and problems with the GEC 4080M computer used for the Mission System Avionics (MSA). Eventually, the 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 Sentry aircraft instead, with proven radar performance, and electronic enhancements to the original USAF systems to address UK-specific requirements. Of the 11 RAF Nimrods that were selected for conversion to AEW3 standard, none returned to the maritime reconnaissance 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 rebuilding 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 as the Nimrod MRA4.

The MRA4 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. The rebuilt aircraft borrows heavily from Airbus technology; the wings are designed and manufactured by BAE Systems (a former Airbus partner) and the glass cockpit is derived from that of the Airbus A340.

The initial in-service date for the MRA4 was scheduled for April 2003. However, development took longer than anticipated and, as of 2009, the aircraft have not yet entered service. The contract was initially for the supply of 21 rebuilt Nimrods. Initially Flight Refuelling Limited were contracted to undertake the conversions to MRA 4 standard, but 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 and the task of converting the existing airframes was transferred to BAE Systems Woodford. Due to technical problems the project was halted, after a design fault was discovered with the new wings. This allowed BAE Systems to design a modification to the wing design before the programme could be restarted. During this time wing assembly was transferred from Chadderton factory to the Woodford site. The British House of Commons Defence Committee, in July 2004, reported a forecast cost of 3.5 billion compared to 2.8 billion approved at Main Gate. They noted that the in-service date had slipped to 2009, compared to the date of 2003 approved at "Main Gate".

Nimrod MRA4

Following public recriminations between the Ministry of Defence and BAE, the development contract was renegotiated for the revised number of 18 aircraft. Officially this is attributed to increased capability and availability MRA4 will provide, but it has been suggested that this is in effect compensation to BAE, who had to absorb the cost increases.

Announcing plans for the future of the British military on 21 July 2004, the Defence Secretary Geoff Hoon detailed plans to reduce the upgrade programme to cover only 16 aircraft and suggested that an eventual fleet of twelve might suffice. On 18 July 2006, BAE received a contract worth 1.1 billion for 12 MRA4s. This involves the completion of three development aircraft and conversion of nine more to production standard. In response to the news of the production contract, Mike Turner, Chief Executive of BAE Systems, said: "The new NIMROD MRA4 is a world leader in terms of maritime patrol platforms and it will give the UK at least 30 years of adaptable capability in maritime reconnaissance and attack operations." The Nimrod MRA4 mission systems enable the crews to gather, process and display up to 20 times more technical and strategic data than in the current aircraft, the MR2. The Searchwater 2000 radar is capable over land as well as water: it can sweep an area the size of the UK every 10 seconds.

On 30 July 2007, the Nimrod MRA4 successfully released the Sting Ray torpedo for the first time. The safe separation trial to demonstrate the ability to deploy this weapon from the MRA4 bomb bay took place at Aberporth range off the coast of West Wales during the 75th flight of development aircraft PA02. Three MRA4 development aircraft have been built and are undergoing an intensive flight-test programme. PA02 achieved its first flight in December 2004 and is being used to test elements of the mission system and the air vehicle.

In September 2007, another milestone was passed with the handover of the Aircraft Synthetic Training Aids (ASTA) from Thales Training & Simulation to BAE Systems. ASTA provides the RAF with a sophisticated synthetic training suite that will allow them to transfer training from the aircraft to the ground-based training system. This will increase the availability of the aircraft for operational missions while optimising flight and mission crew performance and capabilities.

As of 2009, delivery of the first production order aircraft to the RAF is planned for late 2010.

Design

The Nimrod was the first jet-powered Maritime Patrol Aircraft (MPA) of any significance. Earlier MPA designs used piston engines 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. However, the transit to the operational area can be made at high altitude and in a jet aircraft this is not only economical on fuel but fast as well, compared to earlier piston-powered aircraft. After transit, the Nimrod descends to its patrol area altitude.

On patrol at high weight all four engines are used, but as fuel is consumed and weight is reduced, first one engine is shut down and then a second is shut down. This allows 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. For transit back to base, the shut down engines are restarted and the aircraft ascends to altitude.

Operators

United Kingdom

Royal Air Force


Royal Airforce Nimrod Squadrons
SquadronAircraftStation (if available)
No. 42(R) SquadronNimrod MR2RAF Kinloss
No. 51 SquadronNimrod R1RAF Waddington
No. 120 SquadronNimrod MR2RAF Kinloss
No. 201 SquadronNimrod MR2RAF Kinloss

As of late 2006, 15 Nimrod MR2 and 3 Nimrod R1 remain in operation.

Former RAF Squadrons

  • No. 203 Squadron RAF - Nimrod MR1
  • No. 206 Squadron RAF - Nimrod MR1 & MR2

Accidents and incidents

Five Nimrods have been lost in accidents:

  • On the 17 November 1980, a Nimrod MR2 crashed near RAF Kinloss after three engines failed following multiple birdstrikes, killing both pilots. The remaining crew survived.
  • On the 3 June 1984, a Nimrod MR2 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 the 16 May 1995, a Nimrod R1 from RAF Lossiemouth ditched in the Moray Firth after suffering an engine fire whilst on a post-servicing testflight. The MoD inquiry identified a number of technical issues as the cause. There were no casualties.
  • On the 2 September 1995, a Nimrod MR2 crashed into Lake Ontario while participating in the Canadian International Air Show, killing the 7 crew members.
  • On the 2 September 2006, a Nimrod MR2 XV230 crashed near Kandahar, Afghanistan, killing 12 airmen, one marine and one soldier the largest single day loss of UK personnel since the Falklands War. On 23 February 2007, the Ministry of Defence took the decision to ground all MR2 aircraft while investigations were carried out on fuel pumps. The MoD were quick to stress that this was not necessarily related to the crash in Afghanistan.
  • On 5 November 2007, a further mid-air incident took place in XV235 over Afghanistan, when the crew noticed a fuel leak during air to air refuelling operations. After issuing an in-flight mayday, the crew landed the aircraft successfully. This incident is highly significant, coming 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) very similar circumstances. The RAF subsequently suspended air to air refuelling operations for this type.

Specifications (MR2)

General characteristics

  • Crew: 12
  • Capacity: 24 "Persons On Board"
  • Length: 38.65 m (126 ft 9 in)
  • Wingspan: 35.00 m (114 ft 10 in)
  • Height: 9.14 m (31 ft)
  • Wing area: 197.05 m (2,121 sq ft)
  • Empty weight: 39,009 kg (86,000 lb)
  • Max takeoff weight: 87,090 kg (192,000 lb)
  • Powerplant: 4 Rolls-Royce Spey turbofans, 54.09 kN (12,160 lbf) each

Performance

  • Maximum speed: 923 km/h (575 mph)
  • Cruise speed: 787 km/h (490 mph)
  • Range: 8,340-9,265 km (5,180-5,755 mi)
  • Service ceiling: 13,411 m (44,000 ft)

Armament

  • AIM-9 Sidewinder, AGM-84 Harpoon, Sting Ray torpedo, depth charges, nuclear depth bombs (until 1992)

Specifications (MRA4)

General characteristics

  • Crew: 10
  • Length: 38.6 m (126 ft 9 in)
  • Wingspan: 38.71 m (127 ft)
  • Height: 9.45 m (31 ft)
  • Wing area: 235.8 m2 (2,538 sq ft)
  • Empty weight: 46,500 kg (102,515 lb)
  • Max takeoff weight: 105,376 kg (232,315 lb)
  • Powerplant: 4 Rolls-Royce BR710 turbofans, 68.97 kN (15,500 lbf) each

Performance

  • Maximum speed: Mach 0.77
  • Range: 11,119 km (6,910 mi)
  • Service ceiling: 12,800 m (42,000 ft)

Armament

  • AIM-9 Sidewinder, AGM-84 Harpoon, Sting Ray torpedo, depth charges, 4 Storm Shadow