HAWKER SIDDELEY NIMROD

With the approaching retirement of Britain’s ageing Avro Shackleton maritime patrol aircraft in the late 1960s, the British Government issued an Air Staff Requirement Tender for the design, manufacture and delivery of a replacement fleet of high-performance, fixed-wing aerial platforms for anti-submarine warfare with the capability of also engaging and destroying enemy surface vessels.

It was a tender that attracted wide interest from both British and foreign manufacturers offering a range of aircraft from the Lockheed P-3 Orion, Hawker Siddeley Trident to the Vickers VC10 and the De Havilland Comet.

The De Havilland Comet had been the world’s first operational jetliner and was also coming to the end of its operational life but its airframe was still considered relatively modern even though its ancient turbojet engines and long been overtaken by more fuel efficient power-plants.

In fact, some extensive modification work to the Comet’s fuselage, in particularly to its pressurised airframe, had already taken place after some disastrous crashes at the beginning of its operational life, which had dramatically shaken public confidence world wide in the safety of the civilian airline industry.

With full cabin pressurisation technology still in its infancy when the Comet first rolled onto the tarmac, crash investigators concluded that the stresses of full pressurisation placed on long distance high, altitude airliners of the day was simply too much for the older style airframes.

As a result, the Comet became the unintentional testbed for a wide rage of airframe modifications and new pressurisation technology - many of which carry through to today’s fleet of modern airlines.

The Comet submission was approved and after having recently purchased the De Havilland Corporation, Hawker Siddeley basically gutted their entire fleet of Comets and completely refitted them including:

• Further airframe strengthening; 
• Engine replacement with the latest Rolls-Royce Spey Turbofans, which dramatically increased the aircraft’s range;
• Major Fuselage modifications including an internal weapons bay and extended nose and tail, to house the latest electronic warfare sensors and a MAD (magnetic anomaly detector) boom which detected submerged submarines as they passed through the earths magnetic field; and
• Complete re-wiring and avionics throughout and reinforcement of the landing gear and increase in fuel tank capacity.

The advantages of the Nimrod’s turbofan engines included greater speed and altitude capabilities, rendering it more capable of evading detection by submarines, as propeller-driven aircraft are more detectable underwater by standard acoustic sensors.

The Nimrods had a flight endurance of just over ten hours without aerial refuelling; with later versions  fitted to receive mid-air refuelling in response to demands of the Falklands War

At the start of a patrol mission all four engines would normally be running, but, as the aircraft’s weight was reduced by the consumption of onboard fuel, up to two engines could be shut down, allowing the remaining engines to be operated in a more efficient manner. Instead of relying on ram air to restart an inactive engine, compressor air could be cross-fed from a live engine to a starter turbine.

Similarly, the two hydraulic systems on board were designed to be powered by the two inner engines that would always be running. 

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.

Search and rescue (SAR) missions were another important duty of the RAF’s Nimrod fleet and were a common sight in both military and civil maritime incidents. Throughout the Nimrod’s operational life, a minimum of one aircraft was always held in a state of readiness to respond to SAR demands.

The Nimrod featured a large crew of up to 25 personnel, although a typical crew numbered roughly 12, most of whom operated the various onboard sensor suites and specialist detection equipment.

Sensor systems included radar, sonar, and the magnetic anomaly detector; a 'sniffer' could detect exhaust fumes from diesel submarines as well. The Nimrod and its detection capabilities were an important component of Britain's military defence during the height of the Cold War.

The Nimrod featured a sizeable bomb bay in which, in addition to armaments such as torpedoes and missiles, could be housed a wide variety of specialist equipment for many purposes, such as up to 150 sonobuoys for ASW purposes or multiple air-deployed dinghies and droppable survival packs such as Lindholme Gear for SAR missions; additional fuel tanks and cargo could also be carried in the bomb bay during ferrying flights.

Other armaments installed in the bomb bay could also include mines, bombs, and nuclear depth charges; later munitions included the Sting Ray torpedo and Harpoon missile for increased capability.

RAF Nimrods saw action during the Falklands campaign as well as the first Gulf War and the Afghanistan and Iraq Wars with Nimrods being used for operations over Iraq, using the aircraft’s sensors to detect hostile forces and to direct attacks by friendly coalition forces.

The last RAF Nimrod was retired in 2011.

All Hawker Siddely Nimrod Instruments listed below come complete with a detailed, custom-built Scale Model of the Hawker Siddely Nimrod Aircraft on its Magnetic Display Arm; Mango Wood Display Stand & Plaque, plus Printed Fact Sheet featuring photo of instrument in aircraft cockpit - as shown in this P3 Orion example opposite:

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