Introduction: This SAE Aerospace Information Report (AIR) was written because of the growing interest in aircraft installed outdoor engine testing by the Federal Aviation Administration@ airlines@ charter/commercial operators@ cargo carriers@ engine manufacturers and overhaul and repair stations. This document was developed by a broad cross section of personnel from the aviation industry and government agencies and includes information obtained from a survey of a variety of operators of fixed and rotary wing aircraft and research of aircraft and engine maintenance manuals. Purpose: This document will provide aircraft operators with an overview of current industry on-the-wing engine test practices including advantages/disadvantages derived@ test criteria@ capabilities of remote ground based test data acquisition/instrumentation and on board condition monitoring systems@ aircraft installation effects@ and a general discussion of procedures@ data@ equipment and personnel required to perform safe@ accurate@ on-the-wing engine tests. This information is provided as a guide to help operators decide to initiate@ improve@ expand or cease performing installed engine testing.