---
kind: "section"
citation: "14 C.F.R. § 25.4"
title: "14"
number: "25.4"
heading: "Definitions."
url: "https://uscodex.org/cfr/14/25.4"
---

# §25.4. Definitions.

- (a) **For the purposes of this part, the following general definitions apply—**
  - (1) Certification maintenance requirement means a required scheduled maintenance task established during the design certification of the airplane systems as an airworthiness limitation of the type certificate or supplemental type certificate.
  - (2) **Significant latent failure—** is a latent failure that, in combination with one or more specific failures or events, would result in a hazardous or catastrophic failure condition.
- (b) **For purposes of this part, the following failure conditions, in order of increasing severity, apply—**
  - (1) Major failure condition means a failure condition that would reduce the capability of the airplane or the ability of the flightcrew to cope with adverse operating conditions, to the extent that there would be—
    - (i) A significant reduction in safety margins or functional capabilities,
    - (ii) A physical discomfort or a significant increase in flightcrew workload or in conditions impairing the efficiency of the flightcrew,
    - (iii) Physical distress to passengers or cabin crew, possibly including injuries, or
    - (iv) **An effect of similar severity.**
  - (2) Hazardous failure condition means a failure condition that would reduce the capability of the airplane or the ability of the flightcrew to cope with adverse operating conditions, to the extent that there would be—
    - (i) A large reduction in safety margins or functional capabilities,
    - (ii) Physical distress or excessive workload such that the flightcrew cannot be relied upon to perform their tasks accurately or completely, or
    - (iii) **Serious or fatal injuries to a relatively small number of persons other than the flightcrew.**
  - (3) Catastrophic failure condition means a failure condition that would result in multiple fatalities, usually with the loss of the airplane.
- (c) **For purposes of this part, the following failure conditions in order of decreasing probability apply—**
  - (1) Probable failure condition means a failure condition that is anticipated to occur one or more times during the entire operational life of each airplane of a given type.
  - (2) Remote failure condition means a failure condition that is not anticipated to occur to each airplane of a given type during its entire operational life, but which may occur several times during the total operational life of a number of airplanes of a given type.
  - (3) Extremely remote failure condition means a failure condition that is not anticipated to occur to each airplane of a given type during its entire operational life, but which may occur a few times during the total operational life of all airplanes of a given type.
  - (4) Extremely improbable failure condition means a failure condition that is not anticipated to occur during the total operational life of all airplanes of a given type.

## Notes

### Amendments

[Doc. No. FAA-2022-1544, 89 FR 68731, Aug. 27, 2024]

### Authority

Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701, 44702 and 44704; Pub. L. 115-254, 132 Stat 3281 (49 U.S.C. 44903 note).

### Source

Source: Docket No. 5066, 29 FR 18291, Dec. 24, 1964, unless otherwise noted.

### Amendments

[Doc. No. FAA-2022-1544, 89 FR 68731, Aug. 27, 2024]