Airworthiness Directives; The Boeing Company Airplanes

We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 777 airplanes. This AD requires, for certain airplanes, replacing radio altimeter transceivers with upgraded units, and, for all airplanes, replacing low range radio altimeter antennas with new antennas. This AD was prompted by operator reports of erratic low range radio altimeter (LRRA) operation while the airplane is airborne. We are issuing this AD to prevent adverse system responses and flight deck effects that could result in loss of controllability of the airplane or landing short of the runway during landing.