Summary
We propose to adopt a new airworthiness directive (AD) for all The Boeing Company Model 747-200B, 747-200C, 747-200F, 747-300, 747- 400, 747-400D, 747-400F, 747-8F, and 747-8 series airplanes. This AD was prompted by reports of uncommanded movement of the Captain's and First Officer's seats. This proposed AD would require, for the Captain's and First Officer's seats, repetitive horizontal actuator identifications, repetitive checks of the horizontal movement system (HMS), a detailed inspection of the HMS for certain airplanes, and applicable on-condition actions. This proposed AD would also require an inspection to determine the part number and, if applicable, the serial number of the Captain's and First Officer's seats and applicable on- condition actions. This proposed AD would also provide an optional terminating action for the repetitive checks of the HMS for certain airplanes. We are proposing this AD to address the unsafe condition on these products.