The European Aviation Safety Agency (EASA) is requiring inspections of Rolls-Royce Trent 1000 engines powering the Boeing 787.

EASA issued an airworthiness directive after rear seal fins were found missing on some intermediate-pressure turbine (IPT) blades during on-wing inspections and overhaul.

The agency says that “release of an IPT blade rear seal fin may result in downstream, secondary damage, potentially accompanied with engine power loss.” The AD becomes effective on May 2.

EASA orders on-wing borescope inspections—after the first 450 cycles at the latest—that will have to be repeated every 200 cycles. The borescope inspection is also to be performed during engine shop visits. If two or more rear seal fins are found broken or missing, or damage on the rear of a blade or the front of a Stage 1 low-pressure turbine blade has been found and the damage is outside defined limits, the engine has to be removed. This type of blade can still be installed in engines if they are checked as defined by the AD.

EASA says it considers the AD an “interim action” pending the development of a modification that will enhance the capability of the engine to sustain non-uniform loads.