Southwest med motoreksplosjon 17APR18

[LN-MOW]

NTSB har funnet seks sprekker i vftebladet som separerte. Det hadde også over 30.000 cycles.

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 maintenance records, the fan blades from the accident engine were last overhauled 10,712 engine cycles before the accident. At the time of the last blade overhaul (November 2012), blades were inspected using visual and fluorescent penetrant inspections. 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.

In the time since the fan blade overhaul, the accident engine fan blade dovetails had been lubricated 6 times. At the time each of these fan blade lubrications occurred, the fan blade dovetail was visually inspected as required for the fan blades installed in the accident engine.

The NTSB materials group is working to estimate the number of cycles associated with fatigue crack initiation and propagation in the No. 13 fan blade and to evaluate the effectiveness of inspection methods used to detect these cracks.

http://www.b737.org.uk/incident_n772sw.htm