AIA Familiarization Guide – Influencing Parts Tool

What is a life-limited part? (LLP) A part whose failure could result in a Hazardous Engine Effect as defined by the FAA in 14 Code of Federal Regulations (CFR) §33.75 – Safety Analysis.

What is a life limit? A life limit specifies the maximum allowable number of flight cycles for which an engine LLP may be operated. (See 14 CFR §33.70 – Engine life-limited parts.) The life limit ensures that each engine life-limited part is withdrawn from service before hazardous engine effects can occur.

What is an influencing part? 14 CFR §33.70 states that establishing a life limit requires an assessment such that “the combination of loads, material properties, environmental influences and operating conditions, including the effects of other engine parts influencing these parameters, are sufficiently well known and predictable so that the operating limitations can be established and maintained for each engine life-limited part.” These “other engine parts influencing these parameters” are commonly called influencing parts.

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