Helicopter flight test campaign: instrumentation layout, sensor placement strategy, and in-flight acceleration measurements for vibration-related investigations

Abstract This article presents a flight-test campaign conducted to investigate abnormal vibration-related events observed in AS365-K2 helicopters equipped with upgraded engines. The aircraft was instrumented with acceleration sensors at multiple fuselage locations (near doors, floor, main rotor, and center of gravity), inside the radome (surrounding the weather-avoidance radar system), and on the empennage (covering the horizontal stabilizer and the lateral fin). The helicopter was flown under several operating conditions, both with and without an externally mounted armament, ranging from hover to approximately 130 kt within the normal operational envelope. The vibration measurements obtained during real helicopter flight operations are rarely available in the open literature, particularly for military platforms. In this context, the main contribution of this work is twofold: (i) we provide a detailed description of the instrumentation layout and flight-test procedures applied to an operational AS365-K2 aircraft, and (ii) we make publicly available a curated dataset of the acquired time-domain acceleration measurements to support future research in aeroelastic modeling, vibration assessment, structural dynamics, and related analysis. Inspection of the collected data reveals that the vibration response of the aircraft changes significantly under certain operating conditions, with some airframe locations exhibiting non-monotonic trends that are not directly correlated with increasing flight speed. These findings, together with the released dataset, support specialized investigations into phenomena such as buffeting-like vibrations on the empennage, recurrent malfunctioning of electronic devices, and the emergence of atypical fuselage cracks.