Three levels of fan structural analysis are included in this practice: Initial Structural Integrity In-vehicle Testing Durability (Laboratory) Test Methods The Initial Structural Integrity section describes analytical and test methods used to predict potential resonance and@ therefore@ possible fatigue accumulation. The In-vehicle (or machine) section enumerates the general procedure used to conduct a fan strain gage test. Various considerations that may affect the outcome of strain gage data have been described for the user of this procedure to adapt/discard depending on the particular application. The Durability Test Methods section describes the detailed test procedures for a laboratory environment that may be used depending on type of fan@ equipment availability@ and end objective. The second and third levels build upon information derived from the previous level. Engineering judgment is required as to the applicability of each level to a different vehicle environment or a new fan design. This SAE Recommended Practice is applicable to any engine cooling fan application including medium and heavy-duty trucks@ buses@ construction equipment@ industrial@ and agricultural equipment. Some sections are more applicable to engine-driven fans than to hydraulic-driven or electric-motor-driven fans@ especially with respect to speed control. Fan failure modes@ however@ are generally the same regardless of driving modes. The usage of non-metallic construction necessitates areas of evaluation not required by metallic designs. Chief among these are temperature extremes@ moisture content@ impact resistance@ chemical attack@ material purity/homogeneity@ and aging/weathering. Areas of evaluation affecting both metallic and non-metallic fans@ but requiring somewhat different approaches with non-metallic parts@ include natural frequency determination and durability testing. Purpose The purpose of this document is to identify the general methodology for the structural analysis of engine cooling fans@ and to provide expanded information on subset practices within the general methodology@ such that a user of this practice can adapt specific subsets related to a vehicle1 class.