Airworthiness Directives; The Boeing Company Airplanes
Key claim: The FAA is proposing revised safety directives for certain Boeing 757 aircraft to correct errors in previously mandated service instructions for modifying relays and wiring linked to the power transfer unit control valve.
Abstract
(Proposed Rule · Transportation Department, Federal Aviation Administration) The FAA proposes to supersede Airworthiness Directive (AD) 2024-25-09, which applies to certain The Boeing Company Model 757 airplanes. AD 2024-25-09 requires installing new relays and changing certain wire bundles leading to the power transfer unit (PTU) control valve. Since the FAA issued AD 2024-25-09, the FAA determined that the requirements bulletin mandated by AD 2024-25-09 contains errors. In some cases, those errors prevent the actions required by AD 2024-25-09 from being fully accomplished. In other cases, the errors would allow actions that could introduce new hazards affecting the operation and thus the availability of the PTU. This proposed AD would require, depending on the airplane configuration, installing new relays and new connectors, changing certain wire bundles, doing an operational test, and applicable on-condition actions. The FAA is proposing this AD to address the unsafe condition on these products.
Why this matters
Correct service instructions are necessary for operators to carry out mandated safety modifications as intended. This proposal addresses errors in Boeing 757 power transfer unit relay and wiring instructions, rather than establishing a new aircraft-wide safety regime, and the revised requirements are not yet final.