Summary
We are revising an earlier proposed airworthiness directive (AD) for certain Model 747 airplanes and Model 767 airplanes. The original NPRM would have required revising the airplane flight manual (AFM) to advise the flightcrew to use certain procedures during descent in certain icing conditions. The original NPRM resulted from reports of several in-flight engine flameouts, including multiple dual engine flameout events and one total power loss event, in ice-crystal icing conditions. This action revises the original NPRM by revising the text of the proposed AFM revision. We are proposing this supplemental NPRM to ensure that the flightcrew has the proper procedures to follow in certain icing conditions. These certain icing conditions could cause a multiple engine flameout during flight with the potential inability to restart the engines, and consequent forced landing of the airplane.