Posted on July 28, 2016 David Sherman
The Federal Aviation Administration (FAA) is has released new requirements for U.S. airlines operating older Boeing 737 Classic jets to would include regular inspections for widespread metal fatigue in the aft fuselage skins and replacements of some skin panels after 53,000 flight cycles of takeoffs and landings.
The new FAA directives were in a special Boeing service bulletin that was sent last June to airlines operating 258 Boeing Company's 737s; which are all at least 18 years old. Boeing stated
“that at points where the aft fuselage skin is chemically milled to create pockets of thinner-gauge metal, the skin is subject over time to widespread metal fatigue — resulting in thin cracks in hidden parts of the aluminum skin that may not be detected during routine airplane inspections; As an airplane ages, widespread metal fatigue will likely occur, and will certainly occur if the airplane is operated long enough without any intervention.”
The new FAA requirements update a 2009 directive issued after an incident occurred on a Southwest 737 flying from Nashville to Baltimore; whereby, a hole opened in the fuselage of 737 which caused a rapid decompression of the passenger cabin. The pilots were able to land the plane safely with no injuries to anyone on board the plane. The cause of this incident was traced back to a fuselage part tearing; the result of a metal fatigue that caused the aluminum skin to separate along the edge of a chemically milled pocket. Further investigation by the FAA concluded that additional cracks were found in the fuselage skin panels as well as cracks at fastener holes. This incident led to the FAA to understand that metal-fatigue issues are more widespread than originally thought.
Previously, the FAA required inspections to add mandatory modifications; however, with the new safety requirements, replacement of some skin panels will be obligatory. It will cost U.S. airlines an estimated $40 million and more to complete the inspections on all 285 airplanes. With the replacement of the skin panels increase the costs up to an additional $50 million.
The new FAA requirements are in no way related to a separate 2011 incident, when a 5-foot-long hole ripped open in the roof of a 737 Classic during another Southwest Airlines flight from Phoenix. In that case, a National Transportation Safety Board investigation determined that it was caused not by aging metal but by “bad workmanship” during assembly of the airplane.
Share
