Hawker Siddeley Nimrod
From Scramble - The Aviation Magazine
|Hawker Siddeley Nimrod MRA4|
|Role||Maritime patrol aircraft|
|Length||@||126 ft 9 in|
|Wing area||m²||2,538 ft²|
|Maximum takeoff weight||@||231,165 lbs|
|Engines||four BMW Rolls-Royce BR710B3-40 turbofan engines|
|Max speed||@||Mach 0.77|
|Unrefueled range||@||> 6,000 nm|
|Service ceiling||@||42,000 ft|
|Armament||Payload in excess of 12,000lb lbs|
The Hawker Siddeley HS.801 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 fitting of a large weapons bay under the fuselage that can carry and drop aerial torpedoes, mines, bombs and other munitions. Sonobuoys for tracking submarines are dropped from launchers in the rear of the fuselage.
In 1982, the Nimrod MR2 makes its combat debut during the Falklands War. First to deploy were two Nimrod MR1 maritime patrol aircraft to patrol Ascension waters and act as links with the nuclear subs. Later in April, they were replaced by some of the thirteen plus and more modern MR2's. In over a hundred sorties from Wideawake, they flew ahead of the Task Force and provided SAR and radio links and coordinated air refuelling for Victor and Vulcan missions and Harrier staging flights. By the surrender, some MR2's were fitted for air-refuelling and some with Sidewinder AAM's for self defence, but no aircraft equipped with the Harpoon anti-shipping missile were ready in time. An endurance record was established during a 18h 50min sortie.
Afganistan and Iraq
The period between 2001 and 2009 saw MR2s used to conduct simultaneous activity above Iraq and Afghanistan, as well as contributing to the maritime security mission in support of the USA's Operation Enduring Freedom in the Middle East. They were also still flying ASW, maritime counter-terrorism and counter-narcotics sorties as required in the UK. Support for the Afghanistan campaign started in October 2001, with MR2s initially serving in a communications rebroadcast role. The aircraft was subsequently equipped with an L-3 Wescam MX-15 electro-optical/infrared surveillance camera under an urgent operational requirement deal. This saw the aged type become a highly valued part of the UK's deployed intelligence, surveillance, target acquisition and reconnaissance capability, despite lacking the datalinks found on more modern platforms. Installed beneath the aircraft's starboard wing, the MX-15 sensor provides images in three formats: wide and narrow electro-optical, and infrared. An operator position for the equipment was placed next to the aircraft's acoustics stations, and includes a moving map function. In Afghanistan, this was used to slew the sensor on to co-ordinates provided by a forward air controller.
The sustained high pace of activity with the MR2 eventually took its toll, and on 2 September 2006 aircraft XV230 was lost in Afghanistan following a mid-air explosion that happened shortly after refuelling from an RAF Lockheed TriStar tanker. Fourteen British personnel died in the incident. Originally due to have left service several years before the crash, the Nimrod aircraft came under intense public scrutiny following the publication of a Board of Inquiry report into the accident. This found that a fundamental design flaw with the Nimrod's fuel system, combined with the hastily performed air-to-air refuelling modification made for the Falklands conflict, had combined to destroy VX230. A catastrophic fire broke out as overflowing fuel came into contact with super-heated hot air ducts. The type remained in deployment following the accident, but was no longer allowed to undergo in-flight refuelling. But it was eventually withdrawn from theatre in May 2009 for a fleet-wide safety modification. Eleven aircraft, received new hot air ducts and some replacement fuel seals.
Developed to replace the Avro Shackleton and based on the Comet 4 civil airliner. 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.
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, these were once described as "radar calibration aircraft". New Sentinel R1 (ASTOR) aircraft have taken on some duties performed by the R1, and the remaining R1s will be replaced by RC-135V Rivet Joint aircraft. Known upgrades include:
A major modification programme was known as Starwindow. The project had been launched to equip the R1’s with a new Open Systems architecture digital SIGINT suite, probably based on those carried by the RC-135 Rivet Joint aircraft operated by the US Air Force. The Starwindow system incorporates two high-speed search receivers, a wide band digital direction finding system and 22 pooled digital intercept receivers. New workstations were fitted for the ‘specialists’ in the rear of the aircraft. The Starwindow installation on XV249 began in December 1996. In addition to the Starwindow package the R1’s were also fitted with a new ‘Special Signals’ intercept facility with a digital recording and playback suite, an enhanced pulse-signal processing capability and multi channel digital data demodulator.
On 21 September 2005 it was announced that the RAF had completed flight trials and acceptance testing of a new airborne reconnaissance system named Extract that was designed specifically for the three Nimrod R1 SIGINT aircraft. Developed by Raytheon, Extract examines routine radio and radar emissions whilst providing electronic combat support to military commanders and will provide enhanced automated capabilities enabling it to respond to current and future threats. In addition to the Extract system on the Nimrod R1s, the company also supplied ground-based analysis systems and a rear crew trainer,
In addition to the new Extract system, Northrop Grumman was selected to execute a first stage assessment phase for Project Helix, a program to provide a new mission suite, associated ground stations and training facilities to enhance the overall reconnaissance mission capabilities of the Nimrod R1.
Starting in 1975, 32 aircraft were upgraded to MR2 standard, including modernisation of the electronic suite, such as the Thales Searchwater maritime surveillance radar, and (as the Nimrod 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 Sidewinder missiles. 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 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, 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 is mounted in the starboard wing pod for SAR operations. The last MR2 was retired on 31 March 2010, significantly ahead of the planned introduction of the MRA4, which was cancelled altogether later in 2010.
Proposed replacement for the Lancaster-derived, piston-engined Shackleton in the Airborne Early Warning role. The aircraft was to have GEC Marconi radars in a bulbous nose and tail. From the start of the first flight trials in 1982 the project was plagued by cost over-runs and problems with the GEC 4080M computer used for the Mission System Avionics (MSA). Eventually, the MoD cancelled the project in December 1986 and ordered seven E-3D Sentry aircraft instead.
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. In December 1996 BAE was awarded a contract to rebuild 21 MR2s to Nimrod MRA4. In February 2002, the UK Ministry of Defence (MoD) reduced this number to 18 aircraft, citing a perceived reduction in the submarine threat. In July 2004, the MoD announced that this number was to be further reduced to 12 aircraft, reduced to 11 in March 2010. In October 2010, the Nimrod MRA4 was cancelled in the Defence Review, leaving the Royal Air Force without ASW and long range SAR capability. The MRA4 essentially was new aircraft, with new Rolls-Royce BR710 turbofan engines, a new larger wing, and fully refurbished fuselage. Much larger air intakes were required because the airflow of the BR710 engine was significantly higher than that of the original Spey 250. The rebuilt aircraft borrowed heavily from Airbus technology; the wings were designed and to be manufactured by BAE Systems (a former Airbus partner) and the glass cockpit was derived from that of the Airbus A340. Equipped with more than 90 antennae and sensors and containing over six million lines of software code, the MRA4 would have been able to scan an area the size of the UK every 10 seconds. The Nimrod MRA4 would have had an endurance of over 15 hours, equivalent to a range in excess of 11.112 km (6,000 nm).
- The Nimrod review - An independent review into the broader issues surrounding the loss of the RAF Nimrod MR2 Aircraft XV230 in Afghanistan in 2006. ISBN: 9780102962659