On April 20, the Federal Aviation Administration (FAA) issued an Emergency Airworthiness Directive (EAD) requiring operators to inspect fan blades on certain CFM56-7B engines within 20 days.
The emergency AD was prompted by the recent event on a Southwest Airlines 737-700, where one of its CFM56-7B engines failed due to a fractured fan blade, resulting in the engine inlet cowl disintegrating. Debris penetrated the fuselage causing a loss of pressurization and prompting an emergency descent. Although the airplane landed safely, there was one passenger fatality. The FAA warns in the AD that “fan blade failure due to cracking, if not addressed, could result in an engine in-flight shutdown (IFSD), uncontained release of debris, damage to the engine, damage to the airplane, and possible airplane decompression”.
All operators of this engine type have been given 20 days from the date of the AD to perform a one-time ultrasonic inspection (USI) of all 24 fan blade dovetail concave and convex sides to detect cracking.
The inspection requirement applies to CFM56-7B engines. Specifically, engines with more than 30,000 total cycles from new must complete inspections within 20 days. The engine manufacturer estimates the corrective action affects 352 engines in the U.S. and 681 engines worldwide.
Southwest Airlines immediately began inspections and cancelled flights to ensure all of its aircraft were inspected quickly and thoroughly.
In a statement, Southwest reiterated that it warned travelers last week that flight disruptions were possible as it began an accelerated engine inspection program following an April 17 midair engine explosion that killed a passenger. The airline said then that it planned to inspect all engine fan blades made by manufacturer CFM within 30 days.
The incident has piqued the attention of US senators of the FAA’s oversight of airline maintenance. U.S. Senator Chuck Schumer commented that his office found that since 2014, there has been a steady decline in the agency enforcing airline maintenance, with fines down by 70 percent.
Senator Schumer has demanded the agency increase safety checks for all airlines and make sure they look out for aging engine parts and metal.