Summary
We propose to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 777-200 and -300 series airplanes equipped with Pratt and Whitney engines. This proposed AD was prompted by reports of blocked drain lines at the engine forward strut that caused flammable fluid to accumulate in a flammable leakage zone. This proposed AD would require doing the following actions on the left strut and right strut: A one-time cleaning of certain forward strut drain lines; installing new forward strut drain lines and insulation blankets; a leak check of the forward strut drain lines; and repair if any leak is found. This proposed AD would also require revising the maintenance or inspection program, as applicable, to incorporate a certain airworthiness limitation. We are proposing this AD to prevent blockage of forward strut drain lines, which could cause flammable fluids to collect in the forward strut area and potentially cause an uncontrolled fire or cause failure of engine attachment structure and consequent airplane loss.