An investigation into hot gas ingestion by an HH-65A helicopter

This thesis presents the methodology developed to determine if the HH-65A helicopter could be subject to the ingestion of a ship's hot exhaust gases into it's engine intakes while operating from the flight deck of that ship. The research and development was conducted in response to a request by the United States Coast Guard for the United States Navy to determine the answer to the question presented above. The two major areas of preparation included an analysis of the effects of hot gas ingestion and the aerodynamic flow mechanisms by which the hot gases could travel, and the development of a method to determine if hot gases can be ingested by the helicopter. Although not the sole method of data collection and analysis, the use of infrared thermography was identified as the most practical and conclusive method available for this effort. The data were collected by conducting hover maneuvers to determine baseline helicopter power requirements, then conducting actual shipboard landings and launches at sea under various relative wind conditions while recording applicable data. The infrared thermography images were recorded on video tape and digitally on a computer. The results of the data analysis revealed that although there was some interaction of the ship's exhaust gases with the helicopter, they never actually reached the engine inlets. It was concluded that the ingestion of hot gases into the helicopter engine inlets did not occur and should not be a concern during routine helicopter operations aboard this ship. Additionally, the infrared thermography video provided the definitive evidence required to support this conclusion.