SAE AIR5656

This SAE Aerospace Information Report (AIR) provides a methodology for performing a statistical assessment of gasturbine- engine stability-margin usage. Consideration is given to vehicle usage, fleet size, and environment to provide insight into the probability of encountering an in-service engine stall event. Current industry practices, such as ARP1420, supplemented by AIR1419, and engine thermodynamic models, are used to determine and quantify the contribution of individual stability threats. The statistical technique adopted by the S-16 committee for performing a statistical stability assessment is the Monte Carlo method (see Applicable References 1 and 2). While other techniques may be suitable, their application is beyond the scope of this document. The intent of the document is to present a methodology and process to construct a statistical-stability-assessment model for use on a specific system and its mission or application.

The purpose of the Statistical Stability Assessment (SSA) is to provide a quantitative tool for optimizing engine stability margin requirements and provide greater visibility of off-design conditions. It can be applied at the inception of a new project to perform trade studies and support risk assessments; or to a mature project to assess the impact/risk of modifications or changes in operational usage.

This document provides guidelines on the procedures and data that are required to perform the statistical stability assessment. A number of illustrative examples are presented.