# Airworthiness Directives; Transport and Commuter Category Airplanes
> **Rule** · Final rule; request for comments. · Published 2021-12-09 · Effective 2021-12-09 · 86 FR 69984
## Document
- **Document number:** 2021-26777
- **Category:** airworthiness
- **Manufacturer:** Transport and Commuter Category
- **Type:** Rule
- **Action:** Final rule; request for comments.
- **Citation:** 86 FR 69984
- **Publication date:** 2021-12-09
- **Effective date:** 2021-12-09
- **FAA docket:** Docket No. FAA-2021-0953
## Abstract

The FAA is adopting a new airworthiness directive (AD) for all transport and commuter category airplanes equipped with a radio (also known as radar) altimeter. This AD was prompted by a determination that radio altimeters cannot be relied upon to perform their intended function if they experience interference from wireless broadband operations in the 3.7-3.98 GHz frequency band (5G C-Band). This AD requires revising the limitations section of the existing airplane/ aircraft flight manual (AFM) to incorporate limitations prohibiting certain operations requiring radio altimeter data when in the presence of 5G C-Band interference as identified by Notices to Air Missions (NOTAMs). The FAA is issuing this AD to address the unsafe condition on these products.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/2021/12/09/2021-26777/airworthiness-directives-transport-and-commuter-category-airplanes)
---
*AI Analytics · CC0 1.0*