Flight Standards Service

Title:MMEL Policy Letter (PL)-54 Rev 11, Terrain Awareness and Warning System (TAWS)
Summary:This PL provides policy for ground proximity warning system (GPWS) and Terrain Awareness and Warning System (TAWS) MMEL requirements. Revision 11 removes relief and policy guidance for windshear systems as it is addressed by PL-67, Windshear Warning and Flight Guidance System (RWS), Windshear Detection and Avoidance System (PWS). It removes the term “GPWS” and places relief for Runway Overrun Awareness and Alerting System (ROAAS) under a generalized item name of “Surface Awareness System.”
References:

Title 14 of the Code of Federal Regulations (14 CFR)

  • Part 121, Operating Requirements: Domestic, Flag, and Supplemental Operations.
  • Part 135, Operating Requirements: Commuter and On Demand Operations and Rules Governing Persons On Board Such Aircraft.

AC 25-23, Airworthiness Criteria for the Installation Approval of a Terrain Awareness and Warning System (TAWS) for Part 25 Airplanes

Documents for Download:Draft Document (PDF)
Comment Log (MS Word)
Comments Due:April 30, 2026
How to Comment:Email comments to:
Email Comments
Title:MMEL Policy Letter (PL)-72 Rev 5, Wing Icing Detection Lights
Summary:This revision clarifies relief available for wing icing detection lights within the regulatory guidelines of 14 CFR. Adds requirement “Aircraft is not operated in known or forecast icing conditions at night” to relief for airplanes with wing critical surfaces visible from the flight deck (Equipped With Primary Ice Detection System).
References:
  • MMEL Policy Letter PL-25, MMEL and MEL Definitions.
  • MMEL Policy Letter PL-34, MMEL and MEL Preamble.
  • MMEL Policy Letter PL-36, 14 CFR Part 91 MEL Approval and Preamble.
Documents for Download:Draft Document (PDF)
Comment Log (MS Word)
Comments Due:May 05, 2026
How to Comment:Email comments to:
Email Comments

Related Information

Last updated: Tuesday, April 21, 2026