GM3 to AMC 20-189 â Additional GM related to the âSignificantâ
classification
ED
Decision 2020/010/R
In the frame of an engine or propeller TC/STC or of an ETSO article authorisation, the definition of âSignificantâ is based on the anticipation of a potential effect on the product, system, or equipment function that could lead to a Catastrophic, Hazardous or Major failure condition. The goal is to identify and enhance the visibility of OPRs that may pose potential safety risks at the aircraft installation level (see AMCÂ 20-189 paragraph 6.1.4).
For example, in the case of an engine TC, a partial or complete loss of thrust or power is regarded as a Minor Engine Effect, whereas it may have a more severe effect at the aircraft level. Unless the engine manufacturer can confirm that the effect at the installation level is no more than Minor, the OPR would be classified as âSignificantâ. The associated assumptions or mitigations are usually recorded through instructions for installing and operating the engine, e.g. in an engine installation manual.
In the case of an ETSO authorisation, classification of the failure condition is either based on assumptions defined by the applicant, or mandated through the ETSO standard, and is the basis of the safety analysis at the ETSO article level. An OPR is classified as âSignificantâ when the OPR may lead to a functional failure associated with a Catastrophic, Hazardous or Major failure condition.
[Amdt 20/19]
For engine, propeller, or ETSO articles, "Significant" classification identifies operational procedures (OPRs) posing potential safety risks at aircraft installation. This classification anticipates failures (Catastrophic, Hazardous, Major) and enhances OPR visibility. If an engine effect severity at the aircraft level is uncertain, the OPR is "Significant." ETSO failure classification relies on applicant assumptions or ETSO standards.
* Summary by Aviation.Bot - Always consult the original document for the most accurate information.
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