---
kind: "section"
citation: "14 C.F.R. § 121.345"
title: "14"
number: "121.345"
heading: "Radio equipment."
url: "https://uscodex.org/cfr/14/121.345"
---

# §121.345. Radio equipment.

- (a) No person may operate an airplane unless it is equipped with radio equipment required for the kind of operation being conducted.
- (b) Where two independent (separate and complete) radio systems are required by §§ [121.347](/cfr/14/121.347.md) and [121.349](/cfr/14/121.349.md), each system must have an independent antenna installation except that, where rigidly supported nonwire antennas or other antenna installations of equivalent reliability are used, only one antenna is required.
- (c) ATC transponder equipment installed within the time periods indicated below must meet the performance and environmental requirements of the following TSO's:
  - (1) **Through January 1, 1992—**
    - (i) Any class of TSO-C74b or any class of TSO-C74c as appropriate, provided that the equipment was manufactured before January 1, 1990; or
    - (ii) **The appropriate class of TSO-C112 (Mode S).**
  - (2) **After January 1, 1992—** The appropriate class of TSO-C112 (Mode S). For purposes of [paragraph (c)](#c) (2) of this section, “installation” does not include—
    - (i) Temporary installation of TSO-C74b or TSO-C74c substitute equipment, as appropriate, during maintenance of the permanent equipment;
    - (ii) Reinstallation of equipment after temporary removal for maintenance; or
    - (iii) For fleet operations, installation of equipment in a fleet aircraft after removal of the equipment for maintenance from another aircraft in the same operator's fleet.

## Notes

### Amendments

[Docket 6258, 29 FR 19205, Dec. 31, 1964, as amended by Amdt. 121-101, 37 FR 28499, Dec. 27, 1972; Amdt. 121-190, 52 FR 3391, Feb. 3, 1987]

### Source

Source: Docket 6258, 29 FR 19205, Dec. 31, 1964, unless otherwise noted.

### Authority

Authority: 49 U.S.C. 106(f), 40103, 40113, 40119, 41706, 42301 preceding note added by Pub. L. 112-95, sec. 412, 126 Stat. 89, 44101, 44701-44702, 44705, 44709-44711, 44713, 44716-44717, 44722, 44729, 44732; 46105; Pub. L. 111-216, 124 Stat. 2348 (49 U.S.C. 44701 note); Pub. L. 112-95, 126 Stat. 62 (49 U.S.C. 44732 note); Pub. L. 115-254, 132 Stat. 3186 (49 U.S.C. 44701 note).

### Amendments

[Docket 6258, 29 FR 19205, Dec. 31, 1964, as amended by Amdt. 121-101, 37 FR 28499, Dec. 27, 1972; Amdt. 121-190, 52 FR 3391, Feb. 3, 1987]