Thursday, May 22, 2008

NTSB acts to prevent further Boeing 757 wing panel separation incidents

NTSB logoThe U.S. National Transportation Safety Board (NTSB) issued three new Safety Recommendations today (Safety Recommendations A-08-22 through -24) aimed at preventing more in-flight separations of wing panels from Boeing 757 aircraft, such as the incident involving a US Airways aircraft in March of this year. In that incident a 4 foot by 5 foot panel from the upper surface of its left wing separated from the aircraft during the cruise phase of a scheduled passenger flight. The NTSB reported a month later that two of the three clips that secured the leading edge of the panel to the wing had failed due to metal fatigue.

Now the NTSB has expressed concern that "there may be other B757s with cracked and/or improperly oriented clips or lack of spacers, which could lead to support clip failure and a wing fixed trailing edge panel separation. A wing fixed trailing edge panel that separates from the aircraft in flight could impact the tail of the airplane, resulting in the potential loss of controlled flight, or could damage the windows or fuselage, resulting in possible rapid depressurization of the aircraft. Because substantial structural damage can result from an in-flight separation of the wing fixed trailing edge panel, it is imperative that operators ensure that the clips are not cracked and are oriented properly with spacers."

In light of these concerns, the NTSB recommended today, May 22, 2008, that the Federal Aviation Administration (FAA):
  • Require operators of Boeing 757 airplanes to conduct a one-time visual inspection of the upper wing fixed trailing edge panel support beam clips for cracks, proper orientation, and spacers, and to replace cracked clips and reinstall any clips that are improperly oriented or that lack spacers, in accordance with Boeing Service Bulletin 757-57-0027, Revision 2, dated November 14, 1991. (A-08-22)
  • Require operators to report any cracked clips found during the one-time inspection, as requested in Safety Recommendation A-08-22, as well as the part number and orientation of the clips relative to the wing rear spar vertical stiffeners and whether spacers were present; then analyze this information to determine if repetitive inspections are required. (A-08-23)
  • Require Boeing to issue more explicit instructions and figures that clearly illustrate the correct orientation of the clips and spacers that attach the Boeing 757 panel support beam to the wing rear spar vertical stiffeners. (A-08-24)
Here is the link to the full text (with diagrams) of NTSB Safety Recommendations A-08-22 through -24 - issued May 22, 2008 (6-page 'pdf' file)

Incidentally (no pun intended), there have been two more instances of problems with loose wing panels that I know about:

On May 12, 2008, a wing panel separated from Northwest Airlines B757-200 while the aircraft was en route from Los Angeles to Detroit. The separated wing panel damaged the aircraft's horizontal stabilizer, but the crew made a safe emergency landing at Las Vegas.

Then Pacific Business News reported that on May 16, 2008, a Hawaiian Airlines Boeing 767-300 experienced a vibration in a wing while en route from Seattle to Kahului, Maui. The aircraft returned to Seattle where it landed safely. Once on the ground, a loose panel on the trailing edge of a wing was discovered, according to a Hawaiian Airlines spokesman.