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Airworthiness Directive 2021-26777

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AD 2021-26777 · 2021-12-09 · appliance

Airworthiness Directives; Transport and Commuter Category Airplanes

What this AD requires

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.

Which aircraft AD 2021-26777 applies to

MakesThe Boeing CompanyAirbus SasBombardier Inc.Embraer S.A.Gulfstream Aerospace CorporationGulfstream Aerospace LpTextron Aviation Inc.Pilatus Aircraft LimitedFokker Services B.V.Saab Ab, Support And ServicesDehavilland Aircraft Of Canada LimitedAirbus Canada Limited PartnershipAtr-Gie Avions De Transport RégionalYaborã Indústria Aeronáutica S.A.Mhi Rj Aviation UlcBae Systems (Operations) LimitedLockheed Martin Corporation/Lockheed Martin Aeronautics CompanyViking Air LimitedDassault Aviation

Applies to all transport and commuter category airplanes equipped with a radio (also known as radar) altimeter, including but not limited to airplanes for which the design approval holder is one of the listed manufacturers.

Whether AD 2021-26777 actually applies to your aircraft (by serial and installed parts) and whether it’s already complied with comes from that aircraft’s records.

How AD compliance is recorded

A valid compliance record (14 CFR 43.9) states:

Method of compliance — The specific action taken (inspected, replaced, modified) and to what revision.
Date — When the work was done.
Aircraft time — Total time in service / tach at compliance — how recurring next-due is computed.
Signature & certificate — The A&P/IA who returned it to service, with certificate number.
Is AD 2021-26777 complied with on your aircraft?

Tailplate reads a tail number’s logbooks and matches every applicable AD — including this one — to its compliance evidence, with recurring next-due dates computed.

Look up a tail number →Read the full directive (Federal Register)

Applicability is derived from the FAA directive corpus and is advisory, not a legal airworthiness determination. Compliance is established only from an aircraft’s actual records.