Engines on the newest versions of the Boeing 737 must be inspected immediately for signs that a weak part has failed.
The Federal Aviation Administration ordered the action Thursday after learning that broken engine parts prompted two in-flight engine shutdowns last week.
A "telegraphic airworthiness directive" from the agency, second only in urgency to an emergency directive, ordered immediate inspections on 46 engines installed on 23 U.S. airliners, 13 of which are owned by Southwest Airlines. Nine others are owned by Continental Airlines; one is owned by Eastwind Airlines.
The directive also stated that the engine part in question, the accessory gearbox starter gearshaft, had to be replaced on all of the aircraft by Sept. 1 or within the next 750 flight hours, whichever comes first.
The action followed two incidents on June 26 involving the latest versions of the world's most common airliner, the Boeing 737-700 and -800 aircraft. They are equipped with CFM International CFM56-7B turbofan engines, made by a joint venture of General Electric and the French company Snecma.
The pilots for two jets flown by Russia's Transaero Airlines and Norway's Braathens Airlines had to shut off one of their aircraft's two engines after a gearshaft broke. No one was hurt in either incident.
Subsequent investigation determined that the shafts cracked because of high stresses during manufacturing. The process since has been changed.
Boeing spokesman Russ Young said his company, which does not manufacturer the engines, had no comment on the order.
The directive orders the immediate inspection of the magnetic chip detector aboard the right-hand engines on all 737-700 and -800 aircraft. The detector senses metal chips from engine components, a warning sign of engine failure. If the detector contains abnormal magnetic particles, the starter gearshaft must be replaced immediately.
The same routine must occur the following day with the left-hand engine. The gearshaft is located on the left side of the engines, meaning that the one on the plane's right side is closer to the passenger compartment. Officials are concerned about spraying engine parts entering the cabin and hurting passengers.
Regardless of the results of the inspection, all of the gearshafts must be replaced by the end of the summer.
Worldwide, there are 94 such engines installed on 47 airplanes. FAA orders apply only to U.S.-registered airliners, but foreign carriers typically follow the agency's lead on safety matters. The estimated cost of repairs to the U.S. fleet is $536,000.
Written by Glen Johnson ©1998 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed