Summary
We propose to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes. This proposed AD was prompted by reports in which a single, undetected, erroneous radio altimeter output caused the autothrottle to enter landing flare retard mode prematurely on approach. This proposed AD would require removing certain autothrottle computers and installing a new or reworked autothrottle computer. We are proposing this AD to prevent a single, undetected, erroneous radio altimeter output from causing premature autothrottle landing flare retard and subsequent loss of automatic speed control, which could result in loss of control of the airplane.