The US Federal Aviation Administration will limit a fleet of Boeing 787-8s and -9s powered by certain Rolls-Royce Trent 1000 engines from flying on extended operations (ETOPS) routes longer than 140min flight time from the closest diversion airport.
An airworthiness directive will be published on 17 April in response to “several engine failures of Trent 1000 Package C engines”, the FAA says in a notice published on 16 April.
The FAA originally approved the Trent 1000 Package C engine to operate ETOPS routes up to 330min flying distance from the closest diversion airport.
However, R-R began work in October 2016 on a redesign of the stage 2 blades in the intermediate pressure compressor section after discovering a design flaw.
More recently, R-R discovered the problem with the existing Stage 2 IPC blades is more hazardous than they first understood.
The new findings were reported to Boeing officials, who informed the FAA.
As a result, all 787s powered by Trent 1000 Package C engines must operate under the new 140min ETOPS limit within three days of the publication of the airworthiness directive, the FAA says.
The stage 2 blades in the IPC exhibit a resonant frequency that is excited at high thrust settings at certain temperatures and altitudes, the FAA says.
In the event of a single-engine failure on a 787 with a Trent 1000 Package C engine still operating, the remaining engine would have to operate at maximum continuous thrust until the aircraft can descend to land, the FAA says.
“If the remaining engine already had cracked IPC stage 2 blades, the likelihood of the remaining engine failing will further increase before a diversion can be safely completed,” the agency says.