Summary
We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD would require replacement of the thumbnail fairing edge seals on both sides of the engines with Nitronic 60 stainless steel alloy seals. This proposed AD was prompted by reports of excessive in-service wear damage of the thumbnail fairing edge seal and the fan cowl panel rub strip and fan cowl skin assembly. We are proposing this AD to prevent failure of the fire seal, which could allow a fire in the fan compartment to spread beyond the firewall and reach the flammable fluid leakage zones, resulting in an uncontrolled fire.