Twilight of the Mighty Hunter

I had posted back in December about one of the obscure roles performed by the BAe Nimrod during the 1982 Falklands War. More often with ongoing commitments in Iraq and Afghanistan, maritime patrol aircraft like the Nimrod and the Lockheed P-3 Orion are finding themselves performing missions they were not initially designed to perform. During Operation Enduring Freedom in Afghanistan, the onboard high fidelity EO systems of the Orion proved valuable to US Special Forces teams fighting the Taliban. With long endurance, extensive sensor and communication suites and larger crews able to handle multiple tasks, maritime patrol aircraft became ideal in the role of overland ISR (Intelligence, Surveillance, and Reconnaissance).

In 2003 the RAF issued an Urgent Operational Requirement (UOR) to equip several Nimrods with a late-generation EO sensor system, the Wescam MX-15. Four aircraft had the sensor turret mounted in a fairing installed under the starboard wing just inboard of the pinion tank and deployed to Saudi Arabia to assist joint UK-US-Australian special forces teams in scouring the western deserts of Iraq for Scud missile launchers. After the fall of the Iraqi regime, the Nimrods returned to their home base of RAF Kinloss, but were soon recalled to Iraq in the summer of that year to assist in the fight against the insurgency under Operation Paradoxical. Since the RAF didn't yet have any UAVs in the same class as the MQ-1 Predator, the Nimrods with the MX-15 EO system provided high-fidelity overhead real-time ISR for the coalition forces involved. At the time, an early version of the ROVER (Remote Optical Video Enhanced Receiver) called Longhorn was in use that allowed, with much effort and technical issues, troops on the ground to see what the Nimrod overhead was seeing. The current ROVER system is much more user friendly.

In the spring of 2004 British forces in Basra found themselves battling the militia fighters of Shiite cleric Muqtada al-Sadr and once again the MX-15 equipped Nimrods provided overhead ISR for the troops on the ground. At the culmination of the effort against the Sadr Militia, an overhead Nimrod provided targeting information to an orbiting AC-130 Spectre gunship. As Sadr Militia units dispersed throughout the back streets of the city of Al Amarah, the Nimrod crew used the MX-15 system to identify the militia and then hand off the coordinates to the Spectre for destruction.

In the latter half of that year following the stabilization of the Shiite south, the Nimrods shifted their attention to Baghdad in an effort to combat the increase in Sunni insurgent bombings there. A Nimrod would forward deploy from Oman to Basra International Airport with a British army liason officer aboard. Flying almost nightly from Basra, the small Nimrod force was flying over 200 hours a month.

In the overland mission, the Nimrod's three acoustic sensor operators rotated shifts operating the MX-15 turret. The ESM and Searchwater radar operators were in charge of deconfliction over the crowded airspace over Baghdad. Army liason officers worked with the mission commander at the master display to coordinate and disseminate the information from the EO operators on the nine-hour missions. The MX-15 had three cameras- one narrow band, one wide band and one in infrared that were selectable by the operators. The best image is then displayed on a larger monitor over a moving map display that allowed ground units to easily relay to the operators where to look.

In July 2006 the MX-15-equipped Nimrod force switched its attention to Afghanistan in the intensifying effort against the Taliban. With a grueling schedule divided between Iraq and Afghanistan, the Nimrod force finally gave way with the loss of XV230 in September in 2006 with all of its 15 crew being lost. The cause was traced to persistent problems with the Nimrod's air-refueling plumbing system adjacent to hot air ducting. With 11 aircraft remaining in the overall fleet, the UK Ministry of Defense put those aircraft through a modification project that was completed in 2009, but the Nimrods never returned to Afghanistan, their role being taken up by a trio of new RAF aircraft, the General Atomics MQ-9 Reaper, Beechcraft Shadow R.1 ISR (based on the Beech King Air) and the new Bombardier Sentinel R.1 SAR surveillance aircraft (based on the Global Express business jet). In March 2010 the Nimrod MR.2 aircraft were official retired, ending some 30 years' service which began in the icy waters of the North Atlantic hunting Soviet subs and ended over the harsh terrain of Afghanistan hunting insurgents. It's replacement, the Nimrod MRA.4, won't be due to enter service until 2012 at the earliest.

Source: Air Forces Monthly, July 2010. "Secrets of the Nimrod at War", by Tim Ripley, p38-42.

Although progressively improved and more powerful versions of the Bristol Olympus jet engine powered the Avro Vulcan bomber, there were also other versions of the Olympus destined for other aircraft that made their initial flights on specially-converted Vulcan testbed aircraft. In addition, other similarly-equipped Vulcans served to flight test other engines during their development cycles as well.

The first engine to be flight tested on the Vulcan wasn't an Olympus variant, though. That honor goes to the Rolls-Royce Conway low-bypass turbofan. The first prototype Vulcan, tail number VX770, was retrofitted with four Conway engines in 1956 and delivered to Rolls-Royce for the start of the Conway flight test program in August 1957. Unfortunately, VX770 was lost during a Battle of Britain flying display at RAF Syterston in September 1958 when the maneuvers it was performing overstressed the airframe, resulting in the loss of the crew. A second Vulcan bomber, XA902, was then selected to undergo conversion with the Conway engines to replace VX770. The conversion work began at Avro's facilities in December 1958 and was completed in July 1959. The Conway engines used were the Conway 11 engines (RAF designation Conway Mk.102 and 103) which were destined for use on the Handley Page Victor B.2, an upgraded version of the original Victor B.1 model.

The Conway test program called for the engines to be run at cruise power at 40,000 feet- however, at that power setting, the Conway 11s were more powerful than the Olympus engines of the Vulcan and the testbed would have easily exceeded the Vulcan's maximum speed and overstressed the airframe! As a result, the Conway 11 engines had to be operated at lower thrust settings similar to what was used on BOAC's Boeing 707-430 jetliners. It was found that two Conways could be operated at cruise settings as long as the other two engines were run at lower settings. Given that the prototype Vulcan VX770 that was lost wasn't as structurally strong as XA902, it became possible to complete the Conway flight test program.

With the Conway test program complete in 1961, XA902 was then converted to take Rolls-Royce Spey engines on the inboard positions while retaining the Conway 11 engines on the outboard positions. It made its first flight in this configuration in October 1961 to support the Spey development for its use on De Havilland DH.121 Trident, the BAC One-Eleven, the Blackburn Buccaneer S.2 and the Hawker Siddley Nimrod. XA902 would be retired from service in 1963.

In 1962, another early-mark Vulcan B.1 was taken from service to test the Olympus 22R engine that was destined for the BAC TSR.2. Vulcan XA894 was modified with a large ventral nacelle with bifurcated intake on each side of the nose landing gear. Conversion work on XA894 began at Filton in 1960 and it made its first flight with the much more powerful Olympus 22R in February 1962 in support of the TSR.2 development program. In December of that year during a ground run test, an uncontained turbine blade failure resulted in a fire that destroyed XA894. No replacement was needed, though, as the Olympus 22R had completed enough of the needed test points for the TSR.2 program.

In 1964, another Vulcan was pulled from service to serve as an engine testbed, this time it was tail number XA903 which arrived at Filton in January of that year for conversion work to flight test the Olympus 593 in support of the development of the BAC/Aerospatiale Concorde. Using a similar ventral nacelle as had been used on XA894 in the Olympus 22R flight test program, this time instead of a bifurcated intake a straight-through intake was used that resembled a single-engine Concorde engine nacelle. A retractable spray bar was also fitted ahead of the intake and water from a bomb bay water tank was used to test water ingestion and icing conditions on the Olympus 593 engine. The first flight was made with the Concorde engine in September 1966 and the test program finally ended in 1971 with over 400 hours of flight time. With the Olympus 593 at full power, the Vulcan testbed could still fly and maneuver with its own four engines at idle!

Testbed work would continue for XA903, though. In August of 1971 XA903 was flown to Marshalls of Cambridge for conversion work to support the development of the Rolls-Royce/Turbo Union RB.199 engine for the Panavia Tornado program. The ventral nacelle used for the Olympus 593 program was modified by Marshalls to not only accommodate the RB.199 engine, but to replicate the starboard side of the Tornado's fuselage. The first flight with the RB.199 was made in April 1973 and one of the most unusual aspects of the RB.199 flight test program was that the ventral nacelle was even equipped with a Mauser 27mm cannon that would be used on the Tornado. The cannon's location in relation to the intake replicated its location on the Tornado so that gun gas ingestion trials could be carried out. The firing trials were carried out at Boscombe Down but weren't done while airborne- XA903 remained on the ground and firing butts were used while Rolls-Royce and Turbo Union engineers analyzed the engine's performance as gun gas was drawn into the intake. A total of 285 flight hours were accumulated with the RB.199 on XA903 when the Vulcan was finally retired in February 1979, the last early-mark Vulcan B.1 to have flown.

Source: Avro Vulcan- Britain's Famous Delta-Wing V-Bomber by Phil Butler and Tony Buttler. Midland Publishing/Aerofax, 2007, p70-73.

While BAe Nimrod maritime patrol aircraft were deployed to the South Atlantic in 1982 Falklands War to protect the British naval task force from Argentine surface vessels and submarines, the Nimrod also had two little-known roles during that conflict. The first role was that of "the largest fighter aircraft" when AIM-9 Sidewinder missiles were cleared for firing from underwing hardpoints with the intent of targeting the Argentinian's Boeing 707s that were being used to shadow the British naval task force. In addition, the AGM-84 Harpoon missile was cleared for use on the Nimrod in the anti-shipping role, though neither the Sidewinder or the Harpoon were fired in anger during the conflict.

The more obscure role of the Nimrod during the Falklands was that as a back up for the Avro Vulcan "Black Buck" bombing missions. The long range of the Nimrod made it a natural for the overland bombing role and a rudimentary bombsight was configured for use by the co-pilot to drop either 1000 lb air-retarded bombs or BL755 cluster bombs. A trial drop was even conducted at the Garvie Island range in Scotland.

Source: Air Forces Monthly, December 2009. "More Than A Sub-Hunter!" by Jon Lake, 32-35.