---
kind: "section"
citation: "14 C.F.R. § 135.143"
title: "14"
number: "135.143"
heading: "General requirements."
url: "https://uscodex.org/cfr/14/135.143"
---

# §135.143. General requirements.

- (a) No person may operate an aircraft under this part unless that aircraft and its equipment meet the applicable regulations of this chapter.
- (b) Except as provided in [§ 135.179](/cfr/14/135.179.md), no person may operate an aircraft under this part unless the required instruments and equipment in it have been approved and are in an operable condition.
- (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)(2)](#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 16097, 43 FR 46783, Oct. 10, 1978, as amended by Amdt. 135-22, 52 FR 3392, Feb. 3, 1987]

### Authority

Authority: 49 U.S.C. 106(f), 40113, 41706, 44701-44702, 44705, 44709, 44711-44713, 44715-44717, 44722, 44730, 45101-45105; Pub. L. 112-95, 126 Stat. 58 (49 U.S.C. 44730).

### Source

Source: Docket 16097, 43 FR 46783, Oct. 10, 1978, unless otherwise noted.

### Amendments

[Docket 16097, 43 FR 46783, Oct. 10, 1978, as amended by Amdt. 135-22, 52 FR 3392, Feb. 3, 1987]