The order was issued after one of the GE engines failed during a ground test in South Carolina and cracks were found in the fan mid shaft of another engine of the same type two weeks later.
"We are issuing this (directive) because we evaluated all the relevant information and determined the unsafe condition ... is likely to exist or develop in other products of the same type design," says the FAA order, issued Friday.
The order requires an inspection of the fan mid shaft on all GE GEnx-series turbofan engines installed on 787 Dreamliners before their next flight. Periodic re-inspections are required every 90 days or less to check for possible cracking of the mid shaft.
"This condition, if not corrected, could result in failure of the (fan mid shaft) resulting in one or more engine failure(s) and possible loss of the airplane," the FAA directive said.
Due to the urgency of the problem, the FAA bypassed the usual 30-day public comment period before an airworthiness directive takes effect.
"The FAA has found that the risk to the flying public justifies waiving notice and comment prior to adoption of this rule based on the reported engine failure, the crack find, and that the root cause is still somewhat unknown," the FAA's directive said.
The problem was first noticed when a GE engine failed on a new Dreamliner as it was undergoing runway tests at the Charleston, S.C., airport on July 28. Debris was ejected from the engine and fell on the runway, sparking a small fire and forcing the airport to shut down for about an hour.
Then on Aug. 14, an ultrasonic inspection on the same part in another 787's engine found cracking.
The cause of the cracking is not yet determined, but according to the FAA it "is likely due to environmentally assisted cracking; a type of corrosive cracking that is time-dependent." The agency is requiring repetitive inspections at an interval of not more than 90 days.
The FAA said it is working closely with General Electric to resolve the problem.
It was not immediately clear how many Dreamliners have been equipped with the GE GEnx-series engines. The FAA's directive said it will affect 11 engines installed on planes of U.S. registry.
In addition, the GEnx engines are installed on Dreamliners manufactured for Aeromexico, Airberlin, Japan Airlines, Kenya Airways and possibly others.
The Dreamliner jet is one of Boeing's most critical products. The company delivered the first 787 last year following several years of design and production delays. Airlines set record orders for the jet, as its lightweight, high-tech design was expected to offer travelers more comfort, provide airlines significant fuel savings and open up new routes.
Read the FAA airworthiness directive here >>