Radio Altimeter Interference-Tolerance Performance Standards

Current understanding

The FAA is establishing new minimum performance standards requiring radio altimeters on commercial and other aircraft to tolerate out-of-band emissions from terrestrial wireless operations in the adjacent Upper C-band (3.98–4.2 GHz). Compliance is phased with deadlines in 2030 and 2034, timed to FCC authorization of Upper C-band flexible use. The rule is intended to preserve accurate altitude readings—critical for approach, landing, TAWS, and autoland systems—as 5G and other terrestrial services expand into spectrum adjacent to the 4.2–4.4 GHz altimeter band.

Evidence log

• 2026-07-31 — Requirements for Interference-Tolerant Radio Altimeter Systems: cross-connection with upper-c-band-flexible-use: The FAA compliance deadlines (2030/2034) are triggered by FCC authorization of Upper C-band terrestrial flexible use; the two rules are coordinated halves of the same 5G/aviation coexistence framework. (novelty: 3)

Open questions

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