The FAA has ordered United to inspect all its Pratt & Whitney (PW) 4000-series engines for fan blade cracks prior to returning the aircraft they power to the sky.
One of two broken fan blades in the Pratt & Whitney engine that blew up on Saturday above metro Denver. The other was recovered after it fell to the ground. Photo Credit: Courtesy of the National Transportation Safety Board
The Emergency Airworthiness Directive follows the failure of one of those engines on United flight 328 that was scheduled to fly from Denver to Honolulu on Feb. 20. The aircraft instead turned around after engine parts fell from the sky, littering the Denver suburb of Broomfield. No one was injured.
Under the airworthiness directive, United must conduct thermal imaging inspections of each fan blade in its PW4000-series engines. The technology can detect cracks on interior surfaces of the hollow blades, as well as in other areas that can't be seen during visual inspections, the FAA said.
Based on the results of the inspection, the FAA might reduce the required inspection interval for the engines. Previously, airlines were required to inspect PW4000-series engines after every 6,500 flights.
During the Feb. 20 failure, two fan blades in the engine were fractured, with one breaking off at its base prior to falling to the ground. In a preliminary assessment, the National Transportation Safety Board found that the blade had damage consistent with metal fatigue.
United has 52 Boeing 777-200 aircraft with PW4000-series engines, including 24 that were in service prior to the incident. The carrier had already taken those planes out of service prior to the new FAA directive.
The FAA's order technically applies to all U.S. carriers. However, only United has aircraft equipped with PW4000-series engines.