(a) Purpose
This AMC provides an acceptable means of compliance for rotorcraft components evaluation after lightning strike.
(b) Related Certification Specifications
CS 29.610 âLightning and static electricity protectionâ
CS 29.571 âFatigue tolerance evaluation of metallic structureâ
CS 29.573 âDamage tolerance and fatigue evaluation of composite structuresâ
CS 29.1529 âInstructions for Continued Airworthinessâ
(c) Explanation
CS 29.610 requires the protection of rotorcraft structural components, propulsion system, gearboxes, mechanical and hydraulic control systems from lightning damage that could result in catastrophic failures.
However, damage, failure or departure of any rotorcraft component which could endanger the rotorcraft or its occupants must be part of the evaluation.
This AMC provides detailed guidance on damage tolerance evaluation, including residual strength criteria after lightning strike to ensure continuous safe flight and landing.
Each part, the failure of which implies potential catastrophic consequences and that is exposed to damage under lightning conditions, should be subject to further evaluation which includes:
(1) the nature and extent of the lightning damage (threat assessment, damage detectability, etc.);
(2) the demonstration of the functionality of the affected part up to detection;
(3) a static residual strength capability demonstration supported by analysis and/or test;
(4) when found necessary, a fatigue evaluation of a part with lightning damage for the demonstration of the exposure time before detection.
The airworthiness instruction requested after lightning strike (flight manual and maintenance instructions, etc.) should be consistent with the functional, static and fatigue evaluation of the damage consequences (considered to be a partial failure).
A similar approach should be considered for non-metallic components (for composite, see the AMC 20-29 (11c) guidance).
The above approach is also considered to be applicable for parts departure which could preclude continued safe flight and landing.
For non-structural components (e.g. radomes, panels), only static residual strength is requested for part detachment which could preclude continued safe flight and landing.
[Amdt No: 29/11]
AMC1 29.610 defines acceptable means to evaluate rotorcraft components after lightning strikes, covering damage tolerance, residual strength, and fatigue for continued safe flight.
* Summary by Aviation.Bot - Always consult the original document for the most accurate information.
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