Airworthiness Directives; The Boeing Company Model 777-200 and -300 Series Airplanes Equipped With Pratt and Whitney Engines

Résumé

We propose to adopt a new airworthiness directive (AD) for certain Model 777-200 and -300 series airplanes. This proposed AD would require repetitive inspections for hydraulic fluid contamination of the interior of the strut disconnect assembly; repetitive inspections for discrepancies of the interior of the strut disconnect assembly, if necessary; repetitive inspections of the exterior of the strut disconnect assembly for cracks, if necessary; and corrective action if necessary. This proposed AD also provides an optional terminating action for the inspections. This proposed AD results from reports of system disconnect boxes that have been contaminated with hydraulic fluid and, in one incident, led to subsequent cracking of titanium parts in the system disconnect assembly. We are proposing this AD to detect and correct hydraulic fluid contamination, which can cause cracking of titanium parts in the system disconnect assembly, resulting in compromise of the engine firewall. A cracked firewall can allow fire in the engine area to enter the strut and can lead to an uncontained engine strut fire if flammable fluid is present. Cracking of the disconnect box may also reduce the effective