What happened
On the afternoon of October 28, 2016, an American Airlines flight departing from Chicago O’Hare International Airport experienced a significant mechanical failure during the takeoff ground roll. The aircraft, a Boeing 767-323, registration N345AN, suffered an uncontained failure of the right engine which led to an immediate fire. Upon the occurrence of the failure, the flight crew aborted the takeoff and brought the aircraft to a halt on the runway.
As the fire intensified, the flight attendants began an emergency evacuation of the aircraft. During the process, 1 passenger sustained a serious injury, while 1 flight attendant and 1s19 passengers suffered minor injuries. The aircraft sustained substantial damage due to the fire. At the time of the incident, the weather was characterized by visual meteorological conditions.
Findings
Investigation into the engine failure revealed that a stage 2 high-pressure turbine (HPT) disk ruptured. This failure released fragments that caused extensive damage to the aircraft's structure. One piece of the disk pierced the right wing, severed the main fuel line, and breached the fuel tank, while another fragment exited the engine and struck the runway.
Technical analysis of the turbine disk identified low-cycle fatigue as the primary mechanism for the crack formation. Specifically, researchers found a feature known as a "discrete dirty white spot" within the material. The investigation concluded that this specific material anomaly was likely undetectable during both the initial manufacturing inspections and standard maintenance inspections. Additionally, it was noted that the evacuation began while the left engine was still running, as the crew had initiated the evacuation checklist before the engine shutdown sequence was completed.