Incident Summary
During the takeoff roll, the number one engine failed, and the takeoff was aborted at approximately 70 knots. The aircrew taxied the aircraft clear of the runway and stopped on the reverse high-speed turnoff. The aircrew of another company aircraft reported that the number one engine was on fire. No fire warning light illuminated in the cockpit, but the engine was shut down and a fire extinguisher was discharged into it. A subsequent radio call indicated that the engine was still on fire, leading to a second fire extinguisher discharge.
Evacuation
The other two engines were also shut down, and all occupants were evacuated using the emergency exits. Two passengers received serious injuries during the evacuation.
Investigation Findings
Investigation revealed that the second-stage turbine disk had fractured due to fatigue. The fatigue crack initiated at the base of cavities in the bottom of the air seal groove. Both the inside and outside surfaces of the disk air seal groove exhibited signs of fretting, consistent with the mating air seal having moved fore and aft within the groove.