§ 91.220 Radio Altimeter Systems.

(a) After October 31, 2034, unless otherwise authorized by the Administrator, no person may operate an aircraft in the airspace of the 48 contiguous United States and the District of Columbia with a radio altimeter unless the radio altimeter system meets the performance requirements of paragraph (b) of this section.

(b) The radio altimeter system must operate at an altitude of 0-500 feet above ground level in the interference environment defined in table 1 of this paragraph:

Table 1 to Paragraph (b)

Frequency range
(MHz) 		Power flux-
density, single
polarization,
root mean
square
(dBW/m 2/MHz)
3000 ≤ f < 40009.5
4000 ≤ f < 41009.5
4100 ≤ f < 41509.5
4150 ≤ f < 41606.5
4160 ≤ f < 4170−1
4170 ≤ f < 4180−7
4180 ≤ f < 4190−17
4190 ≤ f < 4200−34
4200 ≤ f ≤ 4400−82
4400 < f ≤ 4410−33
4410 < f ≤ 4430−21
4430 < f ≤ 4440−8
4440 < f ≤ 4450−1
4450 < f ≤ 44606.5
4460 < f ≤ 45009.5
4500 < f ≤ 46009.5
4600 < f ≤ 56009.5
[Amdt. 91-384, 91 FR 48697, July 31, 2026]