Editing Hawker Siddeley Nimrod (section)

===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"/>