Autorotation: Building a Live Man's Curve

Research has been carried at the Brazilian Air Commands' Flight Tests and Research Institute and Technological Institute of Aeronautics in order to theoretically analyze, conduct flight tests and propose both design improvements and new requirements for aeronautical regulations aiming the increase of safety during autorotation flight of lightweight, single-engine helicopters. This paper presents a methodology to obtain risk-level curves for each flight profile, analyzing and quantifying influential factors, in order to indicate technical and operational alternatives to reduce such risks. Different influential factors are analytically and numerically analyzed following a flight test campaign such as longitudinal attitude; lateral attitude; pilot reaction time; and workload for the pilot to perform a safe landing in autorotation. At the end of this phase of the study, results and methodology applied confirm that the information about performance and handling qualities of autorotation flight from aeronautical standards and flight manuals are non-conservative and can induce pilots to flight within an unsafe flight envelope. A risk-level curve, named iso-workload diagram, is presented as an alternative tool for the unawareness of these risk areas by operators.