FAA 5G Airworthiness Directive Update

Most operators flying in the U.S. are familiar with the ongoing 5G mobile network expansion around the country and the impact to some aircraft operations. Back in Dec 2021, the FAA had concerns about 5G networks interfering with aircraft radio altimeters due to similar frequencies and published Airworthiness Directive (AD) 2021-23-12. This original AD restricted multiple types of landing operations that rely on radio altimeter input. The presence of 5G at particular airports are identified via notam.

What was restricted?

• Instrument Landing System (ILS) Instrument Approach Procedures (IAP) SA CAT I, SA CAT II, CAT II, and CAT III
• Automatic landing operations
• Manual Flight Control Guidance System operations to landing/HUD to touchdown operation
• Use of EFVS to touchdown under 14 CFR 91.176(a)
• Required Navigation Performance with Authorization Required (RNP AR) Instrument Approach Procedures

For operators holding authorization to perform RNP AR approaches, the 5G restriction had a significant impact, as these procedures are usually published at airports for specific runways that do not have a viable alternative approach due to terrain or airspace constraints.

The Update

The good news is after further analysis, the FAA has determined that 5G C-Band interference does not create an unsafe condition for aircraft conducting RNP AR approaches. RNP AR procedures utilize BARO VNAV and do not rely on direct radio altimeter inputs to determine arrival at altitude minimums or the flight path of the aircraft. Therefore, the FAA no longer prohibits RNP AR procedures in the updated Airworthiness Directive 2023-10-02 which was published in May 2023. The amended AD continues to prohibit the use of the same operations identified in the original AD (AD 2021-23-12) except for the prohibition of RNP AR. Notam’s for RNP AR approaches due to 5G interference have been cancelled at impacted airports.

Business jet operators who have received FAA approval for RNP AR via LOA/OpSpec C384 can now fully utilize these valuable procedures, including Honeywell’s special procedures for KASE and KEGE, which were previously restricted via 5G notam’s during the last winter season.

Operators who have authorizations for HUD or EFVS to touchdown reductions and have aircraft with non-tolerant radio altimeters will have to wait until their OEM’s release an upgrade via an inline filter installation. Operators should contact their OEM for specific availability.

Moving Forward

AFM updates will include information specified in the new AD. For now, operators can insert a printed copy of the new AD limitations (shown below in figure 1) into their AFMs to allow RNP AR approaches, per the instructions in the AD.