The U.
S. Federal Aviation Administration proposed that airlines modify wing-flap wiring on certain Boeing 747-400 models to avoid a risk that the planes won't take off properly.

The FAA is acting after flaps on a 747-400 with Rolls-Royce Group Plc engines automatically retracted during takeoff, it said in an Aug. 5 Federal Register notice. A faulty signal from the engine's control unit led to the retraction, which can impair a plane's ability to take off, the agency said.

The proposed order would cover 98 U.S. aircraft and cost airlines about $85 per plane, the agency said in the notice. Boeing on Jan. 12 recommended modifying the 747-400 aircraft with engines made by General Electric Co. and United Technologies Corp.'s Pratt & Whitney unit, which use the same signal design as the Rolls-Royce models, the FAA said.

The agency said the unsafe condition may result in “reduced climb performance” and cause a “collision with terrain and obstacles or forced landing of the airplane.”

The modification, described as not a “significant regulatory action,” will cost about $8,330 for the industry, the agency said.

The directive won't become final until the FAA reviews public comments, which are due Sept. 20, it said.