On 2 September 2006, Royal Air Force (RAF) Nimrod MR2 XV230 was deployed on a mission supporting coalition ground forces in Southern Afghanistan. During the mission and following the completion of air-to-air refueling with a Tristar Airborne tanker, the Nimrod suffered a airborne fire which was described by an observing Harrier Jet pilot as coming from it starboard wing root and aft fuselage areas. The jet pilot reported the fire led to an explosion at about 3000 feet which resulted in the total loss of the Nimrod and the deaths of 14 crew and passengers. There were conflicting reports from the ground regarding exactly where the fire was emitting from and the height at which the Nimrod exploded.
XV230 at the Waddington Airshow, July 2005 (Image embedded from http://en.wikipedia.org/wiki/Royal_Air_Force_Nimrod_XV230 15/08/2011)
The crash investigation of the Nimrod XV230 was complicated due to the location of its crash site. The aircraft debris landed in a hostile and unstable area with active ground force combat. Combat search and rescue teams and RAF Regiment troops managed to secure the area for approximately 21 hours before the military situation in the area deteriorated. In this short time all the crew’s bodies and flight recording equipment were recovered, and detailed photographs of the fuselage and crash site were taken. Most of the wreckage was subsequently removed by hostile forces.
The Royal Air Force Board of Inquiry (BOI) determined the following primary engineering cause of the fire was the ignition of fuel from the starboard No.7 fuel tank dry bay. The BOI determined the following physical causes of the fire:
1. Fuel Source: The likely source of fuel was suggested to be an overflow of fuel from a blow-off valve to the No.1 fuel tank which caused a tracking of fuel along the fuselage until it pooled in the No.7 dry bay. Alternatively and with a lower probability, it was suggested it could have been a leak from the aircrafts fuel system due to hot leaks causing damage on fuel system seal.
2. Ignition Source: The source of ignition was determined to be contact from an exposed element in the Nimrod’s Cross-feed/Supplementary Cooling Pack (SCP) duct.
Although this investigation was hampered by the complications of its occurrence in an active combat zone, the results were endorsed by two leading air accident agencies, the UK Air Accident Investigation Branch and the United States Air force Safety Center.
Further findings of the BOI suggested a “Safety Case” which was generated between years 2001-2005 on the Nimrod had identified a number of problems with the aircraft. It was stated that it was not in the mandate of the BOI to determine who was responsible for the accident.
THE HADDON-CAVE NIMROD REVIEW
On the 4 December 2007, the British Secretary of State for Defence commissioned the “The Nimrod Review”, which was headed by Mr. Charles Haddon-Cave. The intent of this review was to independently explore the findings of the BOI which suggested there was a wider perspective to the causes of the accident. The review would assess the airworthiness, explore the “Safety Case” findings, identify responsibility, identify lessons to be learnt and put forward recommendations for prevention of future accidents.
KEY NIMROD REVIEW FINDINGS
The review determined the findings of the BOI were correct in determining the ignition source was from the Cross-feed/SCP duct. The inquiry agreed the most likely fuel source came from overflow and the accumulation of fuel in the No.7 tanks dry bay and suggested further evidence after the BOI endorsed the fuel overflow theory. The review did identify two less likely alternative fuel sources.
The review identified latent design defects in the Nimrod MR2 and each of these design defects contributed to the accident. These included the:
1. Fitting of the Cross-feed duct to the design in 1969, by Hawker Siddeley,
2. Installation of the Supplementary Cooling Pack in 1979, by British Aerospace (BAE),
3. Installation of the Air-to-air refuelling system in 1989, by BAE.
It was determined there had been records of previous incidents related to these latent engineering defects. One example was the rupture of the SCP duct in Nimrod XV227 two years prior to the fatal accident.
The review identified failure of the Nimrod Safety Case and organisational causes as key contributors in the accident causation chain (See Accident Causation Model) which led to the loss of Nimrod XV230.
The Nimrod Safety Case
The Nimrod safety case was a mandatory review carried out between 2001 and 2005 by BAE with the British Ministry Of Defence Nimrod Integrated Project Team, and the independent advice of British company QinectiQ . Its purpose was to identify, assess and mitigate catastrophic hazards on the Nimrod MR2.
The safety case was determined to be a failure as it was the opportunity to identify the latent design flaws in the Nimrod MR2 but this did not occur. Haddon-Cave (2009) stated in his report that the loss of XV230 was avoidable and was the best opportunity to prevent this accident. He stated the production of the safety case was full of errors, missed dangers signs and was a ‘story of incompetence, complacency and cynicism’ (Haddon-Cave, 2009). The review was highly critical of all parties involved with the safety case.
The review described the organisational causes of the accident as being apart of the culture and history of the elements of the British Ministry of Defence in charge of the airworthiness and in-service support of RAF aircraft in general. The key organisation causes suggested by the review include:
1. The flow on effects from significant organisational changes including moves from being a functional organisation to project oriented, creation of larger management structures and a focus of outsourcing work to industry.
2. Conflict created by ever decreasing resources within the organisation and ever increasing demand on resources i.e. trying to do more with less.
3. Ignorance of safety warning signs after they had been highlighted.
4. Continual cost cutting and enforced changes led to the eroding of safety and airworthiness’s importance, and created distractions from safety compliance.
5. Organisational problems impacted the ability of the Nimrod Integrated Project team to do their job correctly during the work on the Safety Case.
6. On going requirement for the continued use of an aging aircraft due to the delays in the now cancelled Nimrod replacement (MR4).
7. Poor procurement practices of the British Ministry of Defence affecting other elements of the organisation.
The loss of the Royal Air Force NIMROD XV230 is a compelling example of latent error and defects effect in the accident causation model. Although the primary cause of the fire were the failure of physical aircraft components, the key causes of this fatal aircraft accident can be attributed to latent errors generated by a number of British Defense organisations involved with the Nimrod MR2. In this case, the latent errors lined up, windows of opportunity opened up and the result was the loss of 14 lives and an aircraft. The sad theme of this accident was the signs of an impending aircraft accident were clearly evident and as Haddon-Cave’s (2009) review suggests this accident was avoidable.
Haddon-Cave, C. (2009). The Nimrod Review: An independent review into the broader issues surrounding the loss of the RAF Nimrod MR2 aircraft XV230 in Afghanistan in 2006. London: Stationary Press.
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