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 manufactures 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.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.