SAE ARP5429

This SAE Aerospace Recommended Practice (ARP) applies to fatigue testing of landing gear and landing gear components.

Advancements in fatigue analysis methodology, combined with larger and faster computers, have led to more thorough and accurate fatigue life predictions. Traditional methodology involved the analysis of block loading spectra using S-N curves excluding the effect of plastic strain, residual stresses and the effect of the loading sequence. Today's methodology employs "strain-life' analysis combined with the application of Neuber's equation and the effects of the loading sequence to determine the true state of stress of every load set in a flight-by-flight spectrum. While providing the ability to analyze the "real world' our advancements in analytical methodology have surpassed the practicality of physical testing. While it is relatively simple to analyze a flight-by-flight spectrum, the cost and time required to test a flight-by-flight spectrum is prohibitive.

The purpose of this document is to provide a method and rationale for creating a physical test spectrum which is significantly reduced from the analytical spectrum and yet provides an accurate accumulation of the analytical damage for all critical areas of the article under test. While the focus of this document is the fatigue testing of landing gear, the approach is applicable to most mechanical structures subject to safe life fatigue analyses.