EASA AD US-2019-16-12
Wings - Vertical Stiffeners - Installation / Replacement
Summary
Airworthiness Directive 2019-16-12 is a final rule issued by the Federal Aviation Administration (FAA) addressing The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. It mandates replacement of vertical stiffeners at left and right buttock line 6.15 on the rear spar of the wing center section, along with installation of angle and bonding jumpers, brackets, sealant, and paint. This directive responds to identified cracks in vertical stiffeners and potential ignition sources in the fuel tank due to degraded fault current bonding paths.
What Changed
This AD supersedes Airworthiness Directive 2005-20-01 by requiring replacement of vertical stiffeners with improved parts and additional modifications to restore electrical bonding integrity. It introduces new installation procedures including bonding jumpers and brackets to mitigate the risk of fuel tank ignition sources. The directive also clarifies that Supplemental Type Certificate ST01219SE installations do not affect compliance requirements.
Why It Matters
This directive is critical for maintaining structural integrity of the wing center section by preventing cracks in vertical stiffeners that could compromise the keel beam and flight load capability. It also addresses electrical bonding degradation that could cause ignition sources inside the fuel tank, thereby reducing the risk of fuel tank explosions. Operators, maintenance, and compliance teams must implement these changes to ensure continued airworthiness and safety.
What To Do
Operators of affected Boeing 737 Classic series airplanes must replace the vertical stiffeners at LBL and RBL 6.15 with new improved stiffeners and perform associated installations including bonding jumpers, brackets, sealant, and paint. Compliance with this AD is mandatory by October 9, 2019. Service information from Boeing Alert Service Bulletin 737-57A1269 Revision 2 provides detailed procedures and must be followed.
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