The accident engine fan blades had accumulated more than 32,000 engine cycles since new. Maintenance records indicated the accident engine fan blades had been periodically lubricated as required per the Boeing 737-600/700/800/900 Aircraft Maintenance Manual. According to the
investigative update, the aircraft’s maintenance records indicate, the fan blades were last overhauled 10,712 engine cycles before the accident. After an August 27, 2016, accident in Pensacola, Florida, in which a fan blade fractured, eddy current inspections were incorporated into the overhaul process requirements.
The No.13 fan blade had separated at the root; the dovetail remained installed in the fan disk. Examination of the No. 13 fan blade dovetail exhibited features consistent with metal fatigue initiating at the convex side near the leading edge. Two pieces of fan blade No. 13 were recovered within the engine between the fan blades and the outlet guide vanes. One piece was part of the blade airfoil root that mated with the dovetail that remained in the fan disk; it was about 12 inches spanwise and full width and weighed about 6.825 pounds. The other piece, identified as another part of the airfoil, measured about 2 inches spanwise, appeared to be full width, was twisted, and weighed about 0.650 pound. All the remaining fan blades exhibited a combination of trailing edge airfoil hard body impact damage, trailing edge tears, and missing material. Some also exhibited airfoil leading edge tip curl or distortion. After the general in-situ engine inspection was completed, the remaining fan blades were removed from the fan disk and an ultrasonic inspection was performed consistent with CFM International Service Bulletin 72-1033. No cracks were identified on the remaining blades.