In November 1997 the FAA proposed airworthiness directive (AD) 97-CE-79-AD requiring repetitive inspections of the forward and aft wood wing spars for compression cracks. The proposed AD called for the installation of multiple inspection ports on both the upper and lower wings surfaces. In response to adverse industry comments, the FAA replaced this AD with a new proposal, 98-CE-121-AD, that included a less invasive alternative inspection procedure.
The proposed AD would affect approximately 6,500 U.S. registered airplanes. Many owners of these aircraft had serious reservations regarding the installation of multiple inspection ports on the upper and lower wing surfaces of their aircraft. Most owners held that the installation of large inspection panels on the upper wing surface, and more than 20 inspection holes on the lower wing surface, would seriously degrade the aesthetics of their aircraft and may admit water into the wing, leading to a more serious safety problem. Although the FAA addressed these concerns by including an alternative inspection procedure in the new AD proposal, they failed to include adequate service instructions for the alternative inspection. Additionally, service experience shows that the scope of the required wing spar inspection can be narrowed considerably without degrading the effectiveness of the inspection.
AOPA agrees that, in this particular situation, the potential for in-flight structural wing failure warrants airworthiness action. However, AOPA maintains that a requirement to install more than 20 inspection panels on each wing is an unnecessary burden on affected aircraft owners. Given the alternative inspection procedure developed by the Citabria Owners Group, installing multiple inspection ports is simply unnecessary.
AOPA thanks the FAA for coordinating this rulemaking effort with various industry organizations, including AOPA and the Citabria Owners Group. However, we believe that it is in the best interest of aviation safety to provide aircraft mechanics with all information necessary to safely and correctly conduct any inspection required by an AD. Consequently, AOPA recommends that the FAA include adequate service instructions in the text of 98-CE-121-AD, or provide guidance to aircraft mechanics indicating where they may obtain instructions for conducting the alternative inspection procedure. Additionally, AOPA recommends that the scope of the wing spar inspection required by the proposed AD be limited to the area of the wing spar where compression cracks are likely to first propagate.
AOPA comments to NPRM 99-CE-121-AD, July 15, 1999
FAA amended AD proposal, 97-CE-79-AD, June 4, 1999
FAA AD proposal, 97-CE-79-AD, November 3, 1997