Summary
We propose to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 777-200 and -300 series airplanes. This proposed AD was prompted by reports of hydraulic fluid contamination found in the strut forward dry bay. This proposed AD would require repetitive general visual inspections of the strut forward dry bay for the presence of hydraulic fluid, and related investigative and corrective actions if necessary. We are proposing this AD to detect and correct hydraulic fluid contamination of the strut forward dry bay, which could result in hydrogen embrittlement of the titanium forward engine mount bulkhead fittings, and consequent inability of the fittings to carry engine loads, resulting in the loss or departure of an engine. Hydraulic embrittlement could cause a through-crack formation across the fittings through which an engine fire could breach into the strut, resulting in an uncontained strut fire.