Airworthiness Directives; Bombardier Model DHC-7-100, DHC-7-101, DHC-7-102, and DHC-7-103 Airplanes

The FAA is adopting a new airworthiness directive (AD) for certain Bombardier Model DHC-7-100, DHC-7-101, DHC-7-102, and DHC-7-103 airplanes. This AD requires revising the Airworthiness Limitations section of the Instructions of Continued Airworthiness to include a new, lower life limit for lower wing skins. This AD results from the discovery that, during the manufacture of the lower wing skins, score marks may have been accidentally inscribed around the edge of the lower wing skin doublers. We are issuing this AD to prevent fatigue cracks from developing at the score marks in the lower wing skins, which could result in the structural failure of the wing.