Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing transport category airplane models, as listed above. This proposal would require a modification of the air data computer (ADC) system, which involves installing certain new circuit breakers, relays, and related components, and making various wiring changes in and between the flight deck and main equipment center. For certain airplanes, this proposal also would require accomplishment of various other actions prior to or concurrently with the modification of the ADC system. This action is necessary to ensure that the flightcrew is able to silence an erroneous overspeed or stall aural warning. A persistent erroneous warning could confuse and distract the flightcrew and lead to an increase in the flightcrew's workload. Such a situation could lead the flightcrew to act on hazardously misleading information, which could result in loss of control of the airplane. This actionis intended to address the identified unsafe condition.