# Airworthiness Directives; Various Helicopters
> **Rule** · Final rule; request for comments. · Published 2021-12-09 · Effective 2021-12-09 · 86 FR 69992
## Document
- **Document number:** 2021-26779
- **Category:** airworthiness
- **Manufacturer:** Various
- **Type:** Rule
- **Action:** Final rule; request for comments.
- **Citation:** 86 FR 69992
- **Publication date:** 2021-12-09
- **Effective date:** 2021-12-09
- **FAA docket:** Docket No. FAA-2021-0954
## Abstract

The FAA is adopting a new airworthiness directive (AD) for all helicopters 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 rotorcraft flight manual (RFM) for your helicopter to incorporate limitations prohibiting certain operations requiring radio altimeter data when in the presence of 5G C-Band interference in areas 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/2021/12/09/2021-26779/airworthiness-directives-various-helicopters)
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