Airworthiness Directive · Amendment 39-13635 · Boeing Model 747-400, 747-400D, 747-400F, 757-200, 757-200PF, 757-200CB, 767-200, 767-300, and 767-300F Series Airplanes
Boeing Model 747-400, 747-400D, 747-400F, 757-200, 757-200PF, 757-200CB, 767-200, 767-300, and 767-300F Series Airplanes
Airplanes as listed in Table 1 of this AD, certificated in any category. Table 1 of this AD follows: Table 1--Applicability As Listed in Boeing Service Airplane Model-- Bulletin-- 747-400, 747-400D, 747-400F series Boeing Alert Service Bulletin airplanes. 747-34A2460, Revision 2, dated June 14, 2001. 757-200, 757-200PF, 757-200CB series Boeing Service Bulletin 757- airplanes. 34A0222, Revision 1, dated July 17, 2003. 767-200, 767-300, and 767-300F series Boeing Service Bulletin 767- airplanes. 34A0332, Revision 1, dated April 24, 2003.
This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing transport category airplane models, as listed above. This amendment requires 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 amendment also requires accomplishment of various other actions prior to or concurrently with the modification of the ADC system. For certain airplanes, this amendment also contains an option that will extend the compliance time to accomplish 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 action is intended to address the identified unsafe condition.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
