Mission and Refueling
The aircraft departed at 13:43 for a mission over Afghanistan in support of coalition forces engaging the Taliban. At 15:30, it rendezvoused with an RAF Lockheed TriStar tanker and received fuel in an air-to-air refueling (AAR) procedure lasting 10 minutes. The refueling appeared to pass without incident, and the crew prepared to turn east toward their operational area.
Fire and Smoke Warnings
Eleven minutes after refueling, a bomb bay fire warning was reported, either coinciding with or immediately followed by an elevator bay underfloor smoke warning. The crew reported smoke entering the cabin from both the elevator and aileron bays. Within a minute, the aircraft depressurized as the fire breached the pressure hull, requiring crew members to don oxygen masks. The captain began turning toward Kandahar, declared a MAYDAY, and initiated a descent.
Crew Reports and Explosion
A crew member reported a fire 'from the rear of the starboard engines,' and another reported a fire within the aileron bay. Last radio contact was at 15:46 when the crew acknowledged the Kandahar weather for landing. Around the same time, a Harrier GR7 pilot, several thousand feet above, reported an intense fire close to the starboard fuselage stretching between the wing joint and the starboard engine, and a second fire behind the aircraft from the rear body. At 15:47, the Harrier pilot saw the Nimrod explode. It broke into four sections at a height of between 750 and 1,000 feet.
Casualties
All 14 crew members were killed: F/Sgt Gary Wayne Andrews, F/Sgt Stephen Beattie, F/Sgt Gerard Martin Bell, F/Sgt Adrian Davies, L/Cpl Oliver Simon Dicketts, F/Lt Steven Johnson, Sgt Benjamin James Knight, F/Lt Leigh Anthony Mitchelmore, F/Lt Gareth Rodney Nicholas, Sgt John Joseph Langton, Sgt Gary Paul Quilliam, F/Lt Allan James Squires, F/Lt Steven Swarbrick, and Mne Joseph David Windall.
Investigation
The official investigation was unable to determine positively the source or cause of the fire, as the wreckage could not be investigated at the crash site and only a few small components were recovered. Through limited data, the board deduced the most probable location of the fire was the No. 7 tank dry bay. Probable causes included fuel escape during AAR due to overflow from No. 1 tank or a leak from the fuel system (fuel coupling or pipe), leading to fuel accumulation; alternatively, a hot air leak could have damaged fuel system seals. Ignition likely occurred from contact with an exposed element of the aircraft's crossfeed or SCP pipe work.
Contributory factors included the age of non-structural system components, maintenance policy for fuel and hot air systems, lack of fire detection and suppression in the No. 7 tank dry bay, hazard analysis not correctly categorizing the threat from collocated fuel and hot air components, and failure to identify full implications of successive fuel system changes when incorporating AAR capability. An aggravating factor was the loss of flying controls due to fire damage to hydraulic systems or cables and pulleys.