Summary
We propose to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 747-8 and 747-8F series airplanes. This proposed AD was prompted by a report that static strength analysis has shown that the aluminum transmission aft bearing plate assemblies have inadequate structural strength for one or more of the required load cases, including cases for drive system jam, flap skew, and structural damage tolerance. Inadequate structural strength can result in damage to the transmission aft bearing plate assemblies. This proposed AD would require removing aluminum transmission aft bearing plate assemblies from the flap track and installing titanium transmission aft bearing plate assemblies to the flap track. We are proposing this AD to prevent inadequate structural strength of transmission aft bearing plate assemblies. This condition could result in damaged transmission aft bearing plate assemblies, which could result in incorrect operation and departure of the flapfrom the airplane and consequent loss of controllability of the airplane.