TYPE: Maritime reconnaissance four-jet

PROGRAMME: Original Hawker Siddeley HS 801 Nimrod first flew 23 May 1967 as adaptation of de Havilland D.H.106 Comet airliner. Total of two prototypes (converted Comet fuselages; now withdrawn), 46 Nimrod MR. Mk 1s and three Nimrod R. Mk 1 elint/sigint aircraft built for the RAF. Of these, 35 converted to MR. Mk 2 from 1979 onwards and 11 became Nimrod AEW. Mk 3s, but failed to enter service and were scrapped. MR. Mk 2 fleet of Nos. 42(R), 120, 201 and 206 Squadrons at Kinloss in 1996 totalled 28 (including three in long-term storage), plus one under conversion to R. Mk 1, four scrapped or used for ground instruction and two lost in accidents. Two original R. Mk 1s remain with No. 51 Squadron at Waddington. Following RAF issue of Staff Requirement (Air) 420 for a Nimrod replacement, Dassault Atlantique 3, two versions of Lockheed Martin P-3 Orion (new production from manufacturer of refurbished P-3A/Bs from Loral) and upgraded Nimrod offered as potential solutions. UK official announcement on 25 July 1996 nominated last-mentioned proposal under commercial designation (since abandoned) Nimrod 2000. Although based on existing aircraft, the upgrade involves extensive (80 per cent) reconstruction of the airframe, plus incorporation of many new components, including engines, wings, landing gear and general systems, as well as new flight deck and detection systems. Contract MAR21a/100 awarded January 1997. Initial three development batch (DB) aircraft are conversions of stored Mk 2s, on which work began in early 1997; first delivery originally scheduled to RAF in 2001, followed by IOC in April 2003 on delivery of seventh aircraft; by early 1999, these dates had slipped 23 months due, in part, to excessive weight of new wing. New schedule called for first flight in June 2002; service deliveries in August 2004; IOC in March 2005; and final delivery in December 2008. Critical design review for air vehicle conducted late 1999 and finalised in early 2000 completing weapon system design. However, due to further slippage, prototype was given media debut on 16 August 2002 in expectationof maiden flight before year-end; delivery then stated to be late 2004.
By October 2002, first flight had been rescheduled for second half of 2003 due to discovery of "minor issues during airframe stress testing", although in-service date of March 2005 stated to be unchanged. BAE Systems and MoD announced change to Nimrod contract on 19 February 2003, this including halt to structural work on fourth and subsequent aircraft until risk reduction exercise completed on first three. Unofficial estimates of service-entry revised to 2009.
Ground testing and verification of engineering plans undertaken at Warton on Nimrod MR. Mk 1 prototype XV147. FR Aviation at Hurn, Bournemouth, selected for airframe relifting and upgrading as subcontractor to BAE flying 'green' aircraft to Warton for mission avionics installation; first three (DB) aircraft (XV247/PAI, XV234/PA2 and XV242/PA3, for modification in that order) dismantled at RAF Kinloss and flown to Hurn by Antonov An-124 14 to 16 February 1997; redelivery to Warton originally due late 1999, January and February 2000. Fourth conversion subject, XV251/PA4, to Hurn under own power, 2 November 1998.
Programme revised in early November 1999, when FR Aviation contract cancelled and airframe work transferred to BAE at Woodford. PA1 completed at Hurn; PA2, PA3 and PA4 airfreighted to Woodford in An-124 in November/December 1999 for completion. Fifth subject, XV258/PA5, delivered directly ex-RAF to Woodford on 8 November 1999; further two followed in 2000 and one (a former ground instructional airframe) in October 2001. Wing for initial aircraft delivered from Chadderton to Woodford in September 2000; second aircraft similarly fitted in December 2000.
Short Brothers and various BAE plants supply airframe components and subassemblies. Ground training systems supplied by Thomson TSL.
Boeing supplying and integrating TCCS (tactical command and sensor system); 15-month laboratory test began at Warton in November 1998.
BAE offers the Nimrod MRA. Mk 4 for overseas sale, in which eventuality production would be relaunched. An agreement of June 1996 provided for McDonnell Douglas (now Boeing) to promote the Nimrod as a successor to the US Navy's Lockheed Martin P-3 Orion, with production at St Louis, if successful. This later expired, but the aircraft remained a contender in the US Navy's Multimission Maritime Aircraft (MMA) competition in early 2002, at which time Australia expressed an interest in joining the US programme. However BAE withdrew from MMA on 20 September 2002, citing lack of a US partner.
Static test wing to be mounted on Nimrod AEW. Mk 3 fuselage for 1,000 hour trial, beginning 2004.

CURRENT VERSIONS (specific): PA1: Air vehicle general systems trials; planned 200 sorties, each between 2 and 4 hours.
PA2: Full mission system; airframe and systems tests. Assigned 160 sorties, each 6 hours, including weapons release and environmental tests.
PA3: Mission systems testbed. Assigned 140 sorties, each 6 hours, including integrated platform tests and actual submarine detection trials in Bahamas.

CUSTOMERS: Royal Air Force order was originally 21. In deference to comprehensiveness of rebuild, aircraft issued with new serial numbers ZJ514 to ZJ534. However, in March 2002 it was announced that the contract had been reduced to 18. Initial squadron to be No. 120 at Kinloss, operational from March 2005, using aircraft PA4 to PA11; no further deliveries until 2008.

COSTS: Ordered as £2 billion programme, including training system and initial logistic support, of which 75 per cent of work being placed with UK companies. Boeing TCCS mission system avionics contract valued at US$639 million (1996). Programme cost increased to £2.4 billion by March 1999, equivalent to 0.5 per cent above inflation. In mid-2000, BAE agreed to pay £46 million penalty because of 23-month programme slippage. BAE profits suffered £300 million charge in 2000 to offset expected Nimrod contract losses. Programme cost stated in 2002 to be £2.98 billion. Further £500 million charged to BAE accounts for 2002.

DESIGN FEATURES: World's first jet-powered, land-based maritime patrol and ASW aircraft on original 1969 service entry; remains sole four-jet in this role. Optimised for anti-submarine warfare (ASW), anti-surface unit warfare (ASUW), search and rescue (SAR), maritime reconnaissance and provision of aid to civil authorities, including fisheries protection and operations against terrorism, drug smuggling and blockade running. Combines fast transit to operational area with low wing loading (and, hence, manoeuvrability) when on station. Can cruise on two or three engines to extend endurance. No special ground equipment required for off-base deployments.
Mid-mounted wing, with two engines in each root and auxiliary fuel tank in leading-edge at approximately two-thirds span; wingtip ESM pods; two hardpoints under each wing. Dihedral tailplane with auxiliary fins at one-third span to counter aerodynamic effects of electro-optical turret rotation; fin has large fillet and electrical equipment/ decoy housing pod at tip. MAD tailboom. 'Double bubble' fuselage cross-section, with weapons bay below; latter restructured for Mk 4 and now in two, separated parts. Wing sweepback 20^o at quarter-chord.
Nimrod Mk 4 upgrade extends operational lifetime by 25 years. Compared with original version, new power plant improves fuel consumption by over 20 per cent and thrust by 30 per cent. Larger wing and increased thrust restore performance despite 20 per cent increase in maximum take-off weight.

FLYING CONTROLS: Conventional control surfaces actuated hydromechanically. Plain flaps immediately outboard of engines.

STRUCTURE: All-metal, two-spar wing comprises centre-section, two stub-wings and two outer panels. Integrally machined stringers and machined spars. Fuselage is all-metal, semi-monocoque with pressurised upper component and unpressurised pannier including the weapons bay and nose radome. Pannier segments are free to move, so that structural loads are not transmitted to the pressure cell. Cantilever, all-metal tail surfaces surmounted by glass fibre fintip pod.
Nimrod MRA. Mk 4 introduces new wing centre box and wing inner panels of increased span designed by BAE Filton, built and assembled at Chadderton. Outer wings, to have been retained under BAE proposal, also new-build, as requested by RAF; designed by Filton, manufactured at Prestwick. Centre fuselage designed at Prestwick and built at Brough; lower (unpressurised) fuselage and front fuselage designed at Farnborough and built at Brough; rear fuselage designed by Dassault (France) and built at Brough; tailplane, elevators, rudder and weapons bay doors designed at Prestwick and Farnborough and manufactured at Prestwick and by FR Aviation. Flap actuation system designed by Dowty. Other new items include wingtip pods, fin fillet, fintip pod and (enlarged) finlets. Retained structures, principally the fuselage pressure hull and empennage, are receiving new protective treatment, although all pressure bulkheads and floors are new. Some 80 per cent of the Mk 4 will be newly built.

LANDING GEAR:Retractable tricycle type; all-new Dowty unit in Nimrod MRA. Mk 4. Four-wheel tandem bogie main units; twin nosewheels. Dunlop tyres, wheels and brakes.

POWER PLANT: Four 'marinised', non-afterburning Rolls-Royce BR710 Mk 101 (BR710B3-40) turbofans with FADEC and EICAS, each rated at 68.9 kN (15,500 lb st). Additional 15 to 17 per cent of internal fuel compared with Nimrod MR. Mk 2.

ACCOMMODATION: Two-person flight crew; eight-person tactical team (Tacco 1, Tacco 2, radar, communications, ESM, two acoustics and one sonobuoy loader/general assistant); optional positions for two visual observers. Additional 13 seats for support personnel or replacement crew. Provision for further workstation. Crew areas, front to rear, are flight deck, lavatory, lateral observers' seats with bubble windows, tactical compartment, optional AEO compartment, galley and sonobuoy/general storage area, including crew door. Integral airstairs.

SYSTEMS: Smiths Aerospace flight management system (based on Boeing 737, but with vertical navigation capability). New Normalair-Garrett environmental control system (inlet at base of fin fillet) and hydraulic system. Hot air anti-icing system. Portable data storage system for fanlt analysis and rectification; compatible with Logistics Information Technology System. Honeywell APU in starboard wing trailing-edge. Lucas power-generation system; Normalair-Garrett (OBOGS) oxygen system. Ram-air turbine scabbed to fuselage side, ahead of port wingroot.

AVIONICS: Mission avionics integration by BAE Systems, significant proportion of new equipment being obtained from Airbus and Eurofighter Typhoon programmes. Nimrod MRA. Mk 4 programmed with 5.8 million lines of computer software code.
Comms: Digital communications subsystem by Telephonics; five V/UHF, two HF.
Radar: Thales Avionics Searchwater 2000MR maritime surveillance radar. Modes include pulse Doppler (air-to-air), inverse SAR, weather and swath and spot SAR.
Flight: Smiths Industries navigation and flight management system. Rockwell Collins TCAS II with Thales IFF Mode S transponder; Thales (Sextant) AFCS with autothrottle and vertical hold/select; EGPWS. Two Litton LN-100G laser INS with embedded GPS; Avionics Specialities ground proximity warning and collision-avoidance. Triplex air data system. Rockwell Collins ADF; BAE Systems ILS/VOR/MLS; Flight Data Co MMS, Smiths NAV/FMS, Thales radar altimeter and Rockwell Collins Tacan.
Instrumentation: Thales (Sextant) seven-screen full-colour LCD EFIS, plus EICAS. Based on that of Airbus A330/A340.
Mission: 'Fourth-generation' sensor suite, including Boeing's tactical command sensor subsystem and Smiths Industries' armamment control system conforming to MIL-STD-1760. Mission system comprises four major subsystems linked by five dual redundant MIL-STD-1553B databuses: Communications, DASS, Armament Control and Tactical Command. Tactical display also capable of integrating weather radar, EO/FLIR imagery and defensive aids information. Seven indentical, Boeing-supplied operator consoles integrated with Northrop Grumman (EOSDS) Nighthunter FLIP and LLLTV turret under forward fuselage; two consoles dedicated to acoustics, plus one other reconfigurable as such; EOSDS imagery is recorded and can be transmitted via satcom. Retains CAE ASQ-504(V) AIMS MAD and Computing Devices Canada/Ultra Electronics AQS-970 processor (derived from AQS-971 in Nimrod MR. Mk 2), but MAD now fully integrated with tactical system and with 64-buoy capability. Ultra Link 11, Rockwell Collins Link 16 (JTIDS), MBDA SHF/satcom, Frederick TTY, Raytheon UHF/satcom. Full range of sonobuoys dispensed from four Normalair-Garrett rotary launchers (each holding 10 size A buoys) in the rear fuselage; two single-barrel launchers for high-level release when fuselage pressurised. Internal racks for 180 buoys (or 360 in emergency), including new SR(SA) 903 active sonobuoy. Active search sonobuoy system (ASSS) ordered 2002 in form of Ultra Electronics CAMBS VI. Elta EL/L-8300UK ESM provides all-round coverage, ±35^o in the vertical plane, with rotating antenna beneath fuselage.
Self-defence: Integrated defensive aids subsystem (DASS) by BAE North America, including a Raytheon AN/ALE-50 (MoD) towed decoy, Vicon 78, Thales (Vinten) chaff/flare dispensers (eight chaff, four flare), BAE Systems AN/AAR-57 missile approach warning and BAE AN/ALR-56M RWR, last mentioned being separate from ESM system. Potential for later addition of DIRCM, laser warning receiver and integrated countermeasures system.

ARMAMENT: Smiths armament control system capable of accepting all current and known future maritime patrol weapons. Four underwing hardpoints, each capable of carrying two side-mounted, self-protection Sidewinder AAMs in addition to an anti-ship missile. Weapons bay, with two pairs of doors, is able to carry up to six lateral rows of ASW weapons, including up to nine Sting Ray torpedoes as well as bombs. Maximum load of Harpoon ASM's is four underwing and one in each of two weapon bays.