Development and Testing of a Complementary Sensor Network for Robust Estimation of Maneuver and Gust Loads

In this publication, a sensor and observer network is presented with the primary objective of increasing the robustness of structural loads estimation. This augmentation is achieved through the combination of measurement methodologies and model-based load observers, thereby creating synergistic effects that mitigate the limitations associated with each approach. This work outlines the development of a complementary sensor network, comprising laboratory tests and virtual flight tests. The sensor technologies employed include strain gauges, fiber bragg sensors, inertial measurement units, camera-based optical deformation measurement, and MEMS pressure measurement profiles. For each of these technologies, the laboratory test development and testing process, alongside the derivation of sensor models for virtual testing of the sensor network is presented. Within the context of the sensor network, these redundant and partially complementary sensors are fused through the utilization of both local and central Kalman filters. The local fusion strategy exploits the integral correlation between inertial measurement unit (IMU) and camera data at corresponding observation points, establishing the basis for employing a data-driven local-model network approach wherein local deformations are trained on structural loads data. The central load fusion combines a data association algorithm based on a quadruple-voting scheme and an extended Kalman filter. Based on virtual flight tests considering a load sensor failure, the performance and robustness of the whole sensor network is demonstrated

Evaluation of the noise impact of flap‑tip fences installed on laminar wings

The aeroacoustics of laminar wings and the noise abatement provided by flap-tip fences are studied experimentally on a scaled model installed in the closed test section of a subsonic wind tunnel. The activity has been developed under an international project funded by the European Union through the H2020 Framework Program. The model reproduces an innovative regional aircraft mounting aft-engines and adopting the Natural Laminar Flow concept. Both take-off and landing settings are tested for several combinations of wind tunnel speeds and angles of attack; these configurations being the most critical from the viewpoint of airframe noise generation. A baseline configuration without flap-tip fences is also tested for a comparative study. Noise sources are identified by measuring pressure fluctuations through a phased microphone array. Data are processed using both Conventional Beamforming and CLEAN-SC algorithms to retrieve the sound source maps and the integrated spectra over the areas of interest. Directivity effects are investigated as well by moving the microphone array in different axial positions corresponding to different aircraft polar directivity angles. The wind tunnel data are eventually extrapolated to full scale and projected to flight condition allowing the analysis of the results in terms of Effective Perceived Noise Level (EPNL). Tests provided an extensive characterization of the acoustic behavior of the analyzed model demonstrating the capability of measurements carried out in a non-anechoic environment, to provide reliable data. The longitudinal traversing of the microphones array allowed us to compute, even though qualitatively, the EPNL and thus demonstrated the feasibility of a procedure that can be a reference for the design of future aeroacoustic tests. The effectiveness of the flap-tip fences to successfully reduce the flap side-edge noise has been definitely verified both through the analysis of the acoustic maps retrieved from the beamforming investigation and by the estimation of the overall variation of the EPNL with respect to a baseline reference configuration without low-noise devices

Aeroacoustic wind tunnel testing of a 1:6.5 model scale innovative regional turboprop

The aeroacoustics of an innovative regional turboprop aircraft is experimentally investigated on a 6.5 scaled model. The measurement campaign was performed at the RUAG Large Subsonic Wind Tunnel in Emmen. The model was mounted on a ceiling strut in the 7-by-5 meters test section, not acoustically treated. The aeroacoustic noise generated by the aircraft model was evaluated analyzing the pressure fluctuations acquired through a phased array of 144 microphones installed on a flat-plate on the test section floor. Pressure fluctuations were acquired in different configurations the most important ones being: the baseline solution (no innovative device applied) with engine on and the model equipped with lined Flap. For the engine on configuration, take-off and approach settings were tested, whereas only the landing configurations was investigated for the baseline lined flap comparison. The main parameters varied during the tests were: the propeller thrust, the propeller revolutions per minute, the speed of the air-flow, the incidence angle of the aircraft and the position of the microphone array. Data were processed and then analyzed in the frequency domain and using a conventional beamforming algorithm to retrieve the sound source map over the areas of interest. Source maps were deconvolved with a CLEAN-SC routine and single source contributions determined through integration of auto-powers

Aeroacoustic wind tunnel testing of a 1:6.5 model scale innovative regional turboprop

The aeroacoustics of an innovative regional turboprop aircraft is experimentally investigated on a 6.5 scaled model. The measurement campaign was performed at the RUAG Large Subsonic Wind Tunnel in Emmen. The model was mounted on a ceiling strut in the 7-by-5 meters test section, not acoustically treated. The aeroacoustic noise generated by the aircraft model was evaluated analyzing the pressure fluctuations acquired through a phased array of 144 microphones installed on a flat-plate on the test section floor. Pressure fluctuations were acquired in different configurations the most important ones being: the baseline solution (no innovative device applied) with engine on and the model equipped with lined Flap. For the engine on configuration, take-off and approach settings were tested, whereas only the landing configurations was investigated for the baseline lined flap comparison. The main parameters varied during the tests were: the propeller thrust, the propeller revolutions per minute, the speed of the air-flow, the incidence angle of the aircraft and the position of the microphone array. Data were rocessed and then analyzed in the frequency domain and using a conventional beamforming algorithm to retrieve the soun