Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Boeing Model 737-300, -400, and -500 series airplanes. This proposal would require replacement of the existing autothrottle computer with a new, improved autothrottle computer. This proposal is prompted by reports of asymmetric thrust conditions during flight caused by irregular autothrottle operation in which the thrust levers slowly move apart causing the airplane to bank excessively and go into a roll. The actions specified by the proposed AD are intended to prevent such conditions, which could result in loss of control of the airplane.