Incident Overview
An incident occurred during the takeoff roll when the No. 2 engine experienced a failure of the aft engine mount cone bolt. This was followed by the failure of the secondary support link, a stainless steel cable. With both aft engine support assemblies compromised, the aft section of the engine dropped to within approximately 4 feet of the ground.
Sequence of Events
As a result of the engine sag, the No. 2 thrust reverser actuator assembly contacted the runway surface during rotation. Additionally, one leading edge flap and the forward engine fairing sustained slight damage. The aircraft subsequently returned to the airport and landed without further incident.
Metallurgical Examination
Metallurgical examination of the cone bolt revealed that it failed due to fatigue. The fatigue was most probably caused by improper installation of the bolt, specifically that it was under-torqued when the operator re-installed the engine. The safety cable failed as a result of overstress, probably induced when the aircraft encountered a rough section of runway during the takeoff roll.