and Space Administration

A flight test based research program was performed to investigate the aerodynamics and cooling of a horizontally-opposed aircraft engine installation. Specific areas inves-tigated were the internal aerodynamics and cooling mechanics of the installation, inlet aerodynamics, and exit aero-dynamics. The applicable theory and current state-of-the-art are discussed for each area. Flight test and ground test techniques for the development of the cooling installation and the solution of cooling problems are presented. The results show that much of the internal aerodynamics and cooling technology developed for radial engines are applicable to horizontally-opposed engines. Correlation is established between engine manufacturer's cooling design data and flight measurements of the particular installation. Also, a flight test method for the development of cooling require-ments in terms of easily measurable parameters is presented. The impact of inlet and exit design on cooling and cooling drag is shown to be of major significance