BAe Nimrod MRA4

BAe Nimrod MRA4

In the early 1960s the search for a replacement for the RAF’s Shackleton maritime patrol aircraft was resolved when the MOD decided to order a redesigned version of the Comet airliner – the HS 801 Nimrod. On 19 Jan 1966 a contract for 38 production aircraft was signed and the type entered service in 1969. The Nimrod has proved to be an excellent aircraft and ideally suited for the role it was originally intended – the worlds only jet powered maritime patrol and anti-submarine warfare aircraft. The aircraft were upgraded, from MR1 to MR2, during the late 1970s and early 1980’s, when the Searchwater radar replaced the ASV21 and the new AQS 901 acoustic system was installed. However, by the early 1990s it was becoming apparent that a replacement aircraft was required; the airframe, engines and avionics were all starting to show their age and the only sensible solution was a new aircraft that could take advantage of significant improvements in aerodynamics, engine performance, avionics and onboard equipment.

The basic requirement for the new aircraft was agreed and in Nov 1992 a study took place to determine the outline specification for the replacement aircraft. At first it appeared likely that the MR2s would be given another upgrade and refurbished, but when this proved too expensive, attention switched to the purchase of a new version of the Lockheed P-3 Orion, known as the P-7, that the US Navy intended to purchase. When the US Navy decided not to order the P-7 the programme stalled, leaving the RAF to cast around and consider other options. A competitive tendering phase between potential contractors began in Jan 1995 and then, on 2 Dec 1996, BAe systems were awarded a fixed-price contract as sole prime contractor, design authority and platform & systems integrator for the new aircraft – known then as Nimrod 2000. However, to reduce the overall cost, and in keeping with the MOD/Treasury’s desire for a Commercial Off The Shelf (COTS) solution, BAe proposed using the fuselages from a number of current Nimrod MR2s. The original contract called for 21 fully equipped aircraft, but this figure was later reduced to 18 after the MOD re-assessed the future threats and the improvements gained by the use of updated equipment.

BAe Nimrod MRA4

Perhaps the most significant change that has affected the design of the new aircraft was the disintegration of the old Warsaw Pact and with it the majority of the submarine threat in the North Atlantic. As the threat from Warsaw Pact submarines fell away, and with it the need for the MR2 to help protect UK SSBNs from attendant Soviet SSNs, it was clear that in this new environment more effective use needed to be made of these capable aircraft. In response to these changes, four MR2 aircraft were fitted with electro-optical cameras and these aircraft have been used frequently for overland surveillance missions, a task complimented by the aircrafts extensive communication equipment, enabling it to operate as a very effective comms relay for other units. During Operation Iraqi Freedom, these specially equipped MR2s operated from Prince Sultan Airbase in Saudi Arabia and flew over western Iraq using their cameras and Orange Crop Electronic Support Measures (ESM) equipment in support US, British and Australian Special Forces.

BAe Nimrod MRA4

In recognition of the new roles undertaken by the MR2 and the roles planned for the replacement aircraft, the Nimrod 2000 was renamed the Nimrod Maritime, Reconnaissance and Attack Mk 4 in early 1998. Given the nature of the current threat, there is every likelihood that the new aircraft will spend far more time on reconnaissance, ELINT and comms relay duties, than on traditional maritime patrols, complimenting the 3 continually over-tasked ELINT Nimrod R1s of 51 Sqn.

BAe Nimrod MRA4 - wing removed

The most controversial decision taken by BAe in their study to determine the design for the MRA4, was to refurbish and reuse the fuselages of a number of old Nimrods for the new aircraft. To some extent this decision was driven by the desire of the MOD to procure a derivative of an existing aircraft. Although this decision probably enabled BAe to lower their overall bid for the contract, whilst probably also appearing to be really efficient to some Treasury bean-counter, in the event this decision created some unforseen problems and has contributed significantly to the long delay in the aircraft entering service. In retrospect, it would probably have been easier to have built completely new fuselages and although the original jigs were destroyed by BAe some time ago, reopening a complete assembly line would have enabled any number of aircraft to be built and the aircraft to be marketed and sold to other countries.

BAe Nimrod MRA4 - old and new

The first 3 fuselages to be refurbished were stripped of all equipment and flown from Kinloss to FRA/Serco at Bournemouth Hurn between Feb 14-16 1997, inside an Antonov An-124. FRA/Serco were sub-contracted by BAe to completely re-life the fuselages to give another 25 years of service, but it soon became obvious that they could not meet the planned timetable within the agreed costs. Eventually, the aircraft were transferred back to BAe Woodford for the work to be completed, but by the time everything had been sorted out, this resulted in the entire programme slipping 23 months. To describe the Nimrod MRA4 simply as a refurbished Nimrod MR2 is to ignore the fact that the aircraft that will eventually emerge is to all intents and purposes a new aircraft. In fact the only the parts of the old MR2 fuselage that are being refurbished and retained are the fuselage pressure cell and empennage – everything else including the cabin pressure floor, bomb bay area, wings and undercarriage are newly designed and manufactured.

BAe Nimrod MRA4 cockpit

At the front end, the new ‘all-glass’ cockpit will incorporate a flight deck using automated flight systems, based on modified Airbus 340 technology, allowing a 2 pilot operation without the flight engineer and routine navigator currently employed in the MR2. Some informed commentators view the reduction in front cockpit crew as a mistake, as the addition of a Tactical Display in the cockpit could easily distract the pilots from their most important function – to fly the aeroplane.



BAe Nimrod MRA4 RRD BR710 engines

The new wing, with 12ft more span and comprising a 23% greater area than the old MR2 wing, will also have 4 underwing hardpoints wired to allow the carriage of a variety of weapons including Harpoon, ATARM, ASRAAM, SLAM-ER, Maverick, Sidewinder and Storm Shadow, giving the aircraft an impressive offensive capability. The other really significant difference in the new wing are the much larger air intakes for the four RRD BR710 high-bypass turbofan engines, each one providing some 14,900 lbs of static thrust, These modern high technology modular engines will provide 25% more thrust than the old RR Spey engines and yet use 30% less fuel.

Inside the fuselage, and linked by MIL-STD 1553B databusses, will be a Tactical Command System (TCS) developed by Boeing from their TMS-2000 system and running on fibre optics. The TCS is a powerful data distribution and display programme, using a Windows based operating system that will allow data to be displayed on 7 reconfigurable high-resolution multifunctional workstations. The sensors include the Thales Searchwater 2000MR multimode search radar that can provide pulse Doppler modes for air-to-air search and Synthetic Aperture Radar (SAR) for ground mapping and Inverse Synthetic Aperture Radar (ISAR) for identifying targets. For the ASW task the aircraft will be fitted with the CDC/Ultra UYS503/AQS970 acoustic processor, a development of the excellent system currently installed on the RAAF AP-3C Orion. To provide an advanced visual search capability, the Northrop Grumman Nighthunter Electro-Optical Search and Detection System (EOSDS) will also be installed under the nose in a retractable ball turret. Using TV cameras and infra-red sensors, the EOSDS will add significantly to the aircrafts search and rescue and vessel identification capability. Data taken by the EOSDS will be recorded using the Super VHS format.

BAe Nimrod MRA4

However, perhaps the most significant item of new equipment on the MRA4 will be the Israeli Elta EL/L-8300UK Electronic Support Measures (ESM) suite – which in reality is more of an ELINT system than anything else. This comprehensive and capable system will be able to identify and classify an extensive range of radars carried by ships or aircraft and will be one of a number of items of equipment carried that will give the aircraft a significant ELINT capability and make the aircraft a very useful adjunct to the Nimrod R1. Also fitted will be a fully integrated Defensive Aids Sub-System (DASS) comprising a Radar Warning Receiver (RWR), a Missile Approach Warner (MAW), a Towed Radar Decoy (TRD), chaff dispensers and Infra-Red Countermeasures (IRCM) flares. The communications capability of the MRA4 will be particularly impressive with 5 V/UHF radios, incorporating Have Quick II secure comms, 2 HF radios, a teletype Modem / Link 11 / Link 16 JTIDS data links and SHF SATCOM.

BAe Nimrod MRA4 - internal layout

The fuselage will house the 8 mission crew. Currently these will comprise a radar operator, an ESM operator, a communications manager, two tactical co-ordinators, two acoustic operators and one additional dry operator capable of handling either radar or above water communications as necessary. To make the most efficient use of the available manpower, I would imagine some operators will be cross-trained and additional crew carried depending on the planned mission.

BAe Nimrod MRA4 - PA1 wing at Woodford layout

A number of significant problems have been encountered during the development and construction of the Nimrod MRA4 and these have resulted in lengthy programme delays and the in-service date slipping 6 years from 2003 to 2009. The inability of FRA/Serco to complete the initial work on the fuselage created the first delay. Then a further delay was caused when they tried to attach the new wing to the old fuselage. The old MR2 wings and fuselages were constructed before the days of CAD / CAM and were built in jigs and then mated by tradesmen hammering & filing the metal to fit as BAe Nimrod MRA4 - intakes necessary – as a result each fuselage was slightly different, in some cases by up to 4 inches. Consequently, when a new wing designed on CADDS5 and manufactured with great precision was presented to the old fuselage, unsurprisingly it didn’t fit. It also probably didn’t help that the re-lifted fuselage was designed on a different CAD system, CATIA, and that the teams had used one fuselage to establish certain datum points and then discovered that the first fuselage they worked on was subtly different.

When the Nimrod MRA4 eventually enters service, provided it achieves its design goals, it will be an impressive and capable aircraft with twice the patrol endurance of the MR2. It should have a range of over 6000 miles, an endurance of over 15 hours, carry a much wider range of offensive weapons and have a significant ISTAR capability. In comparison to the proposed Boeing 737-700 BAe Nimrod MRA4 - PA1 under construction MMA, the Nimrod MRA4 will have much longer range, endurance, weapons load and additional capabilities and not forgetting twice the number engines. There is no doubt that the MRA4 is a very complex aircraft – it will carry around 5.4 million lines of computer code, making it around 3 times as complex as the B-2 Spirit stealth bomber. However, at current prices the programme is likely to cost in excess of £3.4 billion and, if the history of this project and MOD procurement in general is anything to go by, the final cost will creep inexorably towards £4 billion, making the eventual aircraft easily be the most expensive ever operated by the RAF.

BAe Nimrod MRA4 - PA1 grond run

Because of the recurring problems with this programme, in Feb 03 the MOD and BAe systems eventually agreed changes to the contract structure. Now the contract for the Research and Development (R&D) phase for the MRA4 has been split from the production phase. Currently only the first 3 aircraft are included in the R&D contract, the production contract for the remaining 15 aircraft will be negotiated when the various systems are validated on the first 3 aircraft. When the dust has settled, I hope that the MOD & BAe both eventually produce honest internal reports of what has gone wrong with this programme and why it happened, but sadly given the nature of these projects, the timescales involved and the changeover of the personnel involved, this is unlikely to ever happen. In retrospect it would have certainly been easier to have just manufactured a completely new fuselage and then perhaps the new aircraft could have been re-named Nemesis or something similar and wouldn’t have carried the ‘baggage’ of being just a refurbished Nimrod MR2.

BAe Nimrod MRA4 - PA1 taxi trials

To put it mildly, the Nimrod MRA4 programme was and still is very ambitious and BAe Systems appear to have completely under-estimated the complexity and quantity of work necessary to achieve their proposal, together with the associated costs. Despite many rumours to the contrary, I very much doubt the aircraft will be ever be cancelled because, when it does eventually enter service, it will add precisely the Network Enabled Capability sought by the MOD and considered essential for the type of conflicts that UK forces are likely to be involved in over the next 3 decades. Huge political, as well as financial, capital has been invested in this aircraft and current reports indicate that the worse may just about be over and that ground runs have already commenced. Hopefully the aircraft should make its first flight by the end of Jul 04, but only the most optimistic observer would suggest that anything other than a long and rocky road still lies ahead.