Airworthiness Directive · Amendment 39-12250 · Boeing Model 747-400, 747-400F, 757-200, 757-200CB, 757-200PF, 767-200, 767-300, and 767-300F Series Airplanes
Boeing Model 747-400, 747-400F, 757-200, 757-200CB, 757-200PF, 767-200, 767-300, and 767-300F Series Airplanes
Model 747-400, 747-400F, 757-200, 757-200CB, 757- 200PF, 767-200, 767-300, and 767-300F series airplanes; equipped with either a warning electronics unit (WEU) or a modular avionics warning electronic assembly (MAWEA) power supply having part number (P/N) 285T0035-201; certificated in any category.
This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747-400, 757-200, 767-200, and 767-300 series airplanes, that currently requires repetitive checks to detect certain failures in the warning electronic unit (WEU) or modular avionic warning electronic assembly (MAWEA); repetitive tests to detect any failure of tactile, visual, or aural alerts generated by the WEU or MAWEA; and corrective action, if necessary. This amendment makes these requirements applicable to other airplanes on which the defective power supplies may be installed, eliminates the repetitive tests for certain airplanes, and increases the interval for the repetitive tests for certain other airplanes. This amendment also requires replacing any subject power supply in the WEU or MAWEA with a new, modified, or serviceable power supply. The actions specified by this AD are intended to prevent failure of the WEU or MAWEA power supplies, which could result in loss of visual, aural, and tactile alerts to the flightcrew. Absence of such alerts could result in the flightcrew being unaware that an immediate or appropriate action should be taken in the event of an 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.
