“The FAA is proposing to replace Airworthiness Directive 2021–23–13, which would apply to all helicopters equipped with radio (also known as radar) altimeters.” (Photo: Honeywell)
The FAA announced Wednesday. Notice of Proposed Rulemaking (NPRM) Applies to all helicopters equipped with radios or radar and altimeters flying in areas where 5G C-band may interfere with device operation.
To maintain the safety of the National Airspace System (NAS), the FAA is proposing interference immunity requirements for radio altimeters (RA) available throughout affected aircraft.
Rotorcraft that meet these proposed minimum performance levels would be permitted to perform prohibited operations in contiguous U.S. airspace and would no longer be required to include Rotorcraft Flight Manual (RFM) restrictions. After July 1, rotorcraft that do not meet the proposed minimum performance levels will be subject to prohibited operations.
However, the FAA is not proposing to require all helicopters to have radio altimeters that meet certain acceptance requirements, as proposed in the Aircraft Transportation NPRM. According to the FAA, airlines will have the option to upgrade to radio altimeter-tolerant rotorcraft by July 1 if they want to circumvent the proposed AD ban.
Some carriers may require a filter to be installed between the radio altimeter and the antenna to increase radio altimeter tolerance. In other cases, adding filters is not enough to address the susceptibility to interference. Therefore, the radio altimeter must be replaced with an upgraded radio altimeter, the FAA said.
At least 19 carriers are expected to expand their 5G networks starting in June. Towers to propagate the signal will be built across the United States.
The concern is that when operating near 5G towers, certain radio frequencies may cause certain radio/radar altimeter altitude readings to be inaccurate, potentially endangering the aircraft and its crew in flight. There is.
According to the FAA, 5G C-band transmissions are starting to expand and are likely to expand further after July 1, and higher frequency transmissions move closer to the spectrum allocation in which radio altimeters operate, increasing the risk of interference. It is said to increase.
According to the Helicopter Association International (HAI), the potential range of 5G C-band signals makes it impossible to use NOTAM or evaluate proposed alternative methods of compliance (AMOC) on a case-by-case basis. It will be.
Current flight restrictions are limited to areas identified in the notification to air missions, but will apply to the entire continental United States by June 3.
The FAA believes that this AD, if adopted as proposed, will be an interim measure. The FAA also anticipates that rotorcraft incorporating equipment approved under the new radio altimeter TSO will be able to operate in contiguous U.S. airspace without 5G C-band-related RFM restrictions.
Once new radio altimeter TSOs are developed, approved, and available, the FAA may consider additional rulemaking.
