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A successful methodology was developed at Boeing Company to investigate hot-gas ingestion in vertical take-off and landing aircraft. It involves sub-scale model testing using specialized test facilities and test techniques. The baseline characteristics of hot-gas ingestion (HGI) and the performance of various HGI reduction techniques were qualitatively evaluated in the Boeing Hover Research Facility. Potential HGI reduction devices were then further tested at scaled pressures and temperatures in HGI facilities at NASA Lewis, Rolls Royce and British Aerospace. One of the successful HGI reduction devices was flight tested. This paper describes the application of Boeing HGI reduction methodology to three specific aircraft configurations.

Experiments were performed to simulate jet plume effects associated with VTOL aircraft in takeoff and cruise modes. A water facility was used to investigate the influence of inclination angle and separation distance on the three-dimensional fountain flowfield generated by two impinging jets operating at a jet Reynolds number of 250,000. Substantial differences in the flow features were observed for different spacings between the jets. Plume effects in cruise mode were simulated by a supersonic unheated jet parallel to a wall. Variation of the distance between the wall and the edge of the plume is shown to have a major controlling effect on the supersonic screech instability.