Alternative procedure to verify the H–V diagram after external installations on helicopters

Abstract Certification of external installations on helicopters, for modifications which CS27/29.865 is not applicable, often requires the showing compliance paragraph CS XX.79—limiting height-speed envelope—which might imply, ultimately, a certain degree H–V testing. Due to implications safety during investigation curve, preliminary analytical advisable, understand whether test can be drastically reduced. Analytical investigation, though, usually based extensive use simulation data, validated dynamic mathematical models, are available applicant. The authors recently proposed an alternative method, analysis set flight tests, meant assess quantitatively different phases physical/mechanical phenomena related emergency maneuver performed by pilot as consequence power loss, within or in proximity curve. More details, autorotation phenomenology reveals that made up and dedicated tests have been each these phases. whole campaign hence gain thorough insight how, specifically part maneuver, modification could affect helicopter characteristic. Depending this substantiation, testing avoided reduced, limiting few meaningful points. method has assessed basket installation, making purposely developed Flight Instrumentation post-processing tools. results conclusions static parameters, acquired with non-intrusive Test Instrumentation, monitors correlates cockpit parameters commands, following back-to-back approach (i.e., pre- post-modification). demonstrated was witnessed EASA found acceptable applicable requirements.