Editing Hawker Siddeley Nimrod (section)

==Design==

===Overview===
The Nimrod was the first jet-powered MPA to enter service, being powered by the Rolls-Royce Spey turbofan engine.<ref name = "Fricker 593"/><ref name = "neal 120">Neal 1970, p. 120.</ref> Aircraft in this role had been commonly propelled by [[piston engine|piston]] or [[turboprop]] powerplants instead to maximise fuel economy and enable maximum patrol time on station. Advantages of the Nimrod's turbofan engines included greater speed and altitude capabilities, and it was more capable of evading detection by submarines, as propeller-driven aircraft are more detectable underwater by standard acoustic sensors.<ref name = "Rininger 69">Rininger 2006, p. 69.</ref> The Nimrods had a flight endurance of ten hours without aerial refuelling. The MR2s were later fitted to receive mid-air refuelling in response to demands of the Falklands War.<ref name = "Rininger 125"/>

[[File:Two Nimrod R1s of 51 Squadron MOD 45132295.jpg|thumb|left|Pair of Nimrod R1s flying in formation, August 2004]]
At the start of a patrol mission all four engines would normally be running; as the aircraft's weight was reduced by fuel consumption, up to two engines could be shut down, allowing the remaining engines to be operated more efficiently.<ref name = "Fricker 593"/> Instead of relying on [[ram-air intake|ram air]] to restart an inactive engine, compressor air could be crossfed from a live engine to a starter turbine. The crossfeed duct was later discovered to be a potential fire hazard.<ref>Haddon-Cave 2009, p. 20.</ref><ref name = "neal 121">Neal 1970, p. 121.</ref> Similarly, the two [[hydraulic system]]s on board were designed to be powered by the two inner engines that would always be running.<ref name = "neal 121"/> Electrical generation was designed to far exceed the consumption of existing equipment to accommodate additional systems installed over the Nimrod's service life.<ref name = "neal 121"/>

The standard Nimrod fleet carried out three basic operational roles during their RAF service: Anti-Submarine Warfare duties typically involved surveillance over an allocated area of the North Atlantic to detect the presence of Soviet submarines in that area and to track their movements. In the event of war, reconnaissance information gathered during these patrols would be shared with other allied aircraft to enable coordinated strikes at both submarines and surface targets.<ref name = "Rininger 69"/> [[Search and rescue]] (SAR) missions were another important duty of the RAF's Nimrod fleet, operating under the Air Rescue Coordination Centre at RAF Kinloss and were a common sight in both military and civil maritime incidents. Throughout the Nimrod's operational life, a minimum of one aircraft was held in a state of readiness to respond to SAR demands at all times.<ref name = "Rininger 69"/>

===Avionics===
[[File:Hawker Siddeley Nimrod MR2P (801), UK - Air Force AN1042029.jpg|thumb|Nimrod MR2 performing a low pass at Alconbury, August 1990]]

The Nimrod featured a crew of up to 25 personnel, although a typical crew numbered roughly 12,<ref name = "Fricker 593"/> most of whom operated the various onboard sensor suites and specialist detection equipment.<ref name = "Rininger 125">Rininger 2006, p. 125.</ref> A significant proportion of the onboard sensor equipment was housed outside the pressure shell inside the Nimrod's distinctive [[pannier]] lower fuselage.<ref name = "neal 120"/> Sensor systems included [[radar]], [[ESM radar detection]] and [[sonar]].The Nimrod and its detection capabilities were an important component of Britain's military defence during the height of the Cold War.<ref>Armfield, Hugh "Air Force Takes Over as Britain's Watchdog." ''The Age'', 26 October 1971. p. 8.</ref>

The Nimrod's navigational functions were computerised, and were managed from a central tactical compartment housed in the forward cabin. Various functions such as weapons control and information from sensors such as the large forward [[doppler radar]] were displayed and controlled at the tactical station.<ref name = "neal 122">Neal 1970, p. 122.</ref> The flight systems and autopilot could be directly controlled by navigator's stations in the tactical compartment, giving the navigator nearly complete aircraft control.<ref name = "neal 128"/> The navigational systems comprised [[Digital data|digital]], [[Analogue electronics|analogue]], and [[electro-mechanical]] elements. The computers were integrated with most of the Nimrod's guidance systems such as the [[air data computer]], [[astrocompass]], [[inertial guidance]] and doppler radar. Navigation information could also be manually input by the operators.<ref>Neal 1970, pp. 122, 126.</ref>

Upon entry into service, the Nimrod was hailed as possessing advanced electronic equipment such as onboard [[digital computer]]s. The increased capability of these electronic systems allowed the RAF's fleet of 46 Nimrod aircraft to provide equal coverage to that of the larger fleet of retiring Avro Shackletons.<ref name = "Fricker 593"/> The design philosophy of these computerised systems was that of a 'man-machine partnership'; while onboard computers performed much of the data sift and analysis processes, decisions and actions on the basis of that data remained in the operator's hands.<ref name = "neal 119"/> To support the Nimrod's anticipated long lifespan, onboard computers were designed to be capable of integrating with various new components, systems, and sensors that could be added in future upgrades.<ref name = "neal 123">Neal 1970, p. 123.</ref> After a mission, gathered information could be extracted for review purposes and for further analysis.<ref name = "neal 128">Neal 1970, p. 128.</ref>

===Armaments and equipment===
The Nimrod featured a sizeable [[bomb bay]] in which, in addition to armaments such as [[torpedo]]es and [[missile]]s, could be housed a wide variety of specialist equipment for many purposes, such as up to 150 [[sonobuoy]]s for ASW purposes or multiple air-deployed [[dinghy|dinghie]]s and droppable [[survival pack]]s such as [[Lindholme Gear]] for SAR missions; additional fuel tanks and cargo could also be carried in the bomb bay during ferrying flights.<ref name = "neal 120"/> Other armaments equippable in the bomb bay include [[naval mine|mine]]s, [[bomb]]s, and [[nuclear depth bomb|nuclear depth charge]]s; later munitions included the [[Sting Ray torpedo]] and [[Harpoon missile]] for increased capability.<ref name = "Fricker 594"/>

[[File:Nimrod MR2P XV231 (5658535796).jpg|thumb|left|The open bomb bay of a Nimrod]]
The Nimrod could also be fitted with two detachable pylons mounted underneath the wings to be used with missiles such as the [[Martel (missile)|Martel]];<ref name = "neal 120"/> two specialised pylons were later added to enable the equipping of AIM-9 Sidewinder missiles, used for self-defence purposes against hostile aircraft.<ref name = "Rininger 125"/> A powerful remote-controlled searchlight was installed underneath the starboard wing for SAR operations.<ref name = "neal 120"/> For reconnaissance missions, the aircraft was also equipped with a pair of downward-facing cameras suited to low and high-altitude photography.<ref name = "neal 120"/> In later years a newer [[electro-optics|electro-optical]] camera system was installed for greater imaging quality.<ref>Haddon-Cave 2009, p. 18.</ref>

Various new ECMs and electronic support systems were retrofitted onto the Nimrod fleet in response to new challenges and to increase the type's defensive capabilities; additional equipment also provided more effective means of identification and communication.<ref name = "neal 127">Neal 1970, p. 127.</ref><ref>Friedman 1997, pp. 522, 567.</ref> A number of modifications were introduced during the 1991 Gulf War; a small number of MR2s were fitted with improved [[MIL-STD-6011|Link 11]] datalinks, new defensive ECM equipment including the first operational use of a towed radar decoy, and a [[forward looking infrared]] turret under the starboard wing.<ref name="New role p53-4"/>