FAA

EASA

Regulation/standard

CFR 14 25.1309 - Airworthiness standards equipment

Failure condition:

1. Reducing ability of crew to cope with adverse operating conditions.

・ Improbable

CS 25.1309 - Equipment, systems and installation design requirements Failure condition:

1. Major

・ Remote

2. Hazardous

・ Extremely remote

Guidance Material (Advisory Circular - CS AMC)

AC 25.1309-1A - Failure conditions

1. Minor: Crew actions well within capabilities - slight increase in workload - some inconvenience to occupants.

・ Probable

・ >1 × 10⁻⁵/fh

2. Major:

- Conditions impairing crew efficiency or some discomfort to occupants;

- Higher workload or physical distress such that crew can’t be relied upon to perform tasks accurately or completely.

・ Improbable

・ ≤1 × 10⁻⁵ - > 1 × 10⁻⁹/fh

AMC 25.1309 - Failure conditions

1. Minor: Crew actions well within capabilities-slight increase in workload - some physical discomfort to cabin crew or passengers.

・ Probable

・ >1 × 10⁻⁵/fh (Table 2)

2. Major:

- Conditions impairing crew efficiency or discomfort to flight crew

- Physical distress to cabin crew or passengers, possibly including injuries

・ Remote

・ ≤ 1 × 10⁻⁵ - > 1 × 10⁻⁷/fh.

3. Hazardous: excessive workload or physical distress such that flight crew can’t be relied upon to perform tasks accurately or completely - serious or fatal injury to a small number of occupants other than flight crew.

・ Extremely remote

・ ≤1 × 10⁻⁷ - > 1 × 10⁻⁹/fh

Anticipation of failure conditions

・ Probable: One or more times during entire operational life of each aeroplane;

・ Improbable (FAA): Will not occur during entire operational life of a single random aeroplane - may occur occasionally during life of all aeroplanes of type;

・ Remote (EASA): Unlikely to occur to each aeroplane during its total life, but may occur several times during life of a number of aircraft of type;

・ Extremely remote (EASA): Will not occur to each aeroplane during its life but may occur a few times during total life of all aeroplanes of type.

Compliance shown by analysis and where necessary, appropriate ground, flight or simulator tests.