Dassault-Breguet Mystère-Falcon 900B, G-HMEV
As the aircraft was climbing through FL 130 after takeoff from Farnborough there was a loud bang and the No 3 Engine Bay fire warning activated. The crew shut down the engine and fired the extinguisher first shot; the fire warning ceased. The aircraft diverted to Gatwick and landed without further incident. It was found that the No 3 Engine low pressure (LP) turbine assembly had suffered major disruption. Debris from the turbine assembly ruptured the engine casing, penetrated the cowling and caused slight damage to the horizontal stabiliser. Many of the fractured parts were lost overboard but the available evidence indicated that the failure had probably resulted from the fracturing of an LP turbine blade, leading to the loss of rotational restraint for the turbine stators and the spin-up and non-contained rupture of the stators. One of the Stage 2 blades had signs of a casting defect and fracturing of this blade probably initiated the turbine assembly break-up. However, there had also been a substantial number of previous cases of Stage 3 blade fracture and it was possible that such a failure caused the turbine assembly damage. The engine manufacturer has taken measures aimed at preventing turbine blade failure. However, the possibility that casting defects could be present in Stage 2 blades produced prior to these measures and remaining in service could not be dismissed. The turbine casing had been ruptured in some of the previous cases of blade failure, but not where the newer of two available standards of casing had been fitted. The engine manufacturer issued Service Bulletins in the latter part of 2007 recommending replacement of the casing with the later standard but this modification had not been mandated. Two Safety Recommendations have been made.