Boeing 737s around the world face fresh scrutiny

A 5-foot section of the passenger cabin roof of a 15-year-old Boeing 737-300 tore off April 1, forcing the Southwest Airlines flight to make an emergency landing.
None of the 118 people aboard was seriously injured, but light-headed passengers were banged around the cabin and had to quickly put on overhead oxygen masks as pilots made a rapid descent.

The planes will now be subjected to repeated examinations as the problem revealed by tiny, hard-to-find stress fractures in the aluminum skin resonates through the world’s 737 fleet for years to come.

The Boeing 737 is workhorse of international aviation. Airlines and governments are giving the planes a closer look and taking swift action. “We’re not required to inspect them right now, but we felt it was the prudent thing to do, and to help the industry determine the proper interval,” spokesman Paul McElroy said.

There are about 6,000 737s in operation worldwide, and an emergency FAA order only covers 579 that have the type of “lap joint” that failed during last week’s flight. Lap joints are used in many places on an aircraft fuselage and get their name because it is the spot where the aluminum skin of the aircraft overlaps and is secured with rivets. The FAA order focuses on a Boeing joint design on planes made between 1993 and 2000.

Experts say that all of the planes around the world will be covered by the FAA order because of international agreements between civil aviation regulators globally. Many of the inspection orders handed down by foreign governments mirrored the one issued by the FAA.

The FAA said all of the planes have to undergo inspections when they reach the threshold of 30,000 takeoffs and landings. The 175 of those planes that have already reached the threshold are getting immediate inspections.  The inspections are high-tech and labour-intensive.

Mechanics using a device that sends magnetic signals through metal to detect unseen cracks will scan about 50 feet of the twin metal seams running along the top of each airplane. The task takes two experts in aircraft service about eight hours. Repairs on any fatigue cracks will take a day or two at most. The checks will have to be repeated every 500 flights.

Boeing redesigned the lap joint on 737s in the early 1990s and thought airlines wouldn't need to inspect them closely until 60,000 flights. That was a mistake, a top Boeing engineer acknowledged this week.