Fri, May 23, 2008
Says Panels Should Be Inspected For Missing, Cracked Clips
Following a March incident involving
a Boeing 757-200 flying for US Airways, on Thursday the National
Transportation Safety Board issued three recommendations to address
loose, cracked, and incorrectly-fastened wing panels on the
type.
As ANN reported, on March 22
a Boeing 757-225 operated by US Airways as flight 1250 experienced
an in-flight separation of the left upper wing fixed trailing edge
panel during cruise flight at FL270 enroute from Orlando, FL, to
Philadelphia, PA. The panel struck several windows toward the
middle of the aircraft, cracking the outer pane of one window. The
inner failsafe pane was undamaged, and the pressurization of the
aircraft was not compromised.
No emergency was declared, and the airplane landed at
Philadelphia International Airport about 30 minutes after the
separation occurred. None of the 174 passengers or six crewmembers
was injured.
To date, the panel has not been recovered. The B757 upper wing
fixed trailing edge panel is a rectangular panel approximately four
feet by five feet, with approximately half of the forward side of
the panel attached to the panel support beam, which is in turn
attached to the wing rear spar vertical stiffeners using three
support clips and spacers.
The NTSB says if these attachment points fail -- as what appears
to have happened to flight 1250 -- air can flow under the panel,
causing it to lift off the wing and separate. The National
Transportation Safety Board’s investigation of this incident
is ongoing; however, examination of the left wing revealed that the
three support clips had fatigue cracks, and the mechanic who
removed the clips reported that no spacers had been installed.
Additionally, the clips were oriented incorrectly.
The NTSB issued the following recommendations to the 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)
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