Overview
ISO 2669:1995 - "Environmental tests for aircraft equipment - Steady‑state acceleration" specifies laboratory tests that simulate the gradually changing acceleration environment experienced by civil aircraft equipment during maneuvers (turn, pull‑out, roll, etc.). This second edition (1995) cancels and replaces ISO 2669:1978. The standard defines two types of steady‑state acceleration tests, establishes five severity grades of acceleration, and sets requirements for test apparatus and procedures. Note: emergency landing cases are excluded (see ISO 7137).
Key topics and technical requirements
- Types of test: functional tests (equipment operating during acceleration) and structural tests (strength/stiffness and safety under acceleration). The relevant equipment specification must state which type applies.
- Severity grades: five acceleration severity grades are defined to represent different operational conditions; the standard includes tabulated acceleration values for functional and structural testing.
- Equipment categories: equipment is classified (categories A, B, C) according to operational requirements - e.g., whether operation is required during/after acceleration or only structural integrity is critical. Category C (emergency devices like crash recorders) requires the most severe combined testing.
- Test apparatus: a centrifuge is recommended to produce steady‑state acceleration; alternative linear acceleration methods (inflight test bed) may be used in special cases. Apparatus must provide the specified acceleration within ±10% at all test points and be fitted with adjustable acceleration and mass‑balance systems to compensate for imbalance.
- Measurement and monitoring: acceleration can be measured by accelerometer, angular velocity pickup, or other methods; placement may be at the geometric centre, centre of mass, or rotary surface as appropriate. The accuracy of acceleration measuring devices must be one‑third of the tolerance specified in the equipment specification (or better).
- Mounting and orientations: test items must be mounted to allow testing in six orthogonal attitudes (up, down, forward, aft, left, right). Functional and structural test sequences, intermediate and final measurements, and visual inspections are prescribed.
Applications and users
ISO 2669:1995 is intended for:
- Aircraft equipment manufacturers (avionics, instruments, actuators)
- Environmental test laboratories and centrifuge facilities
- Certification authorities and design approval engineers
- Installation and mounting designers (fastenings, anti‑vibration mountings)
- Maintenance organizations validating equipment behavior under maneuver loads
Typical uses include qualification of avionics and mechanical assemblies for maneuver loads, verification of mounting integrity and anti‑vibration performance, and detection of functional degradation (jamming, travel reduction, performance shifts) under steady‑state acceleration.
Related standards
- ISO 7137 - Environmental conditions and test procedures for airborne equipment (referenced for emergency landing cases and broader environmental testing).
