Flight Vibration Testing of the T-FLEX UAV using Online Modal Analysis

Flight testing of the UAV demonstrator T-FLEX in the EU project FLIPASED has provided a platform to demonstrate the capabilities of an online modal identification system based on miniaturized hardware. The system uses data from Micro Electro Mechanical System MEMS sensors via a real time interface to the Flight Control Computer FCC. The signal processing, modal analysis and mode tracking using machine learning are performed using state of the art algorithms in Python and run on the Onboard Computer OBCII which is a Raspberry Pi 4. The data is encoded and transmitted via radio frequency RF telemetry to a ground station, where it is decoded and plotted in an interactive GUI. The natural frequencies and damping ratios can be visualized as a function of time, Mach number or altitude. This allows engineers on the ground to assess the flutter stability of the aircraft in real time during flight testing. A flight test campaign at the DLR airport Cochstedt served as the first deployment of the flutter monitoring system. The system was demonstrated to function robustly without bugs or system failures and was capable of running in real time. The modal parameters were identified with high certainty and could be accurately tracked throughout the flight envelope. The integration of the online modal analysis system with the onboard flight control system for active flutter control will be the next logical progression of the developed system

Conjugation of haloalkanes by bacterial and mammalian glutathione transferases: Mono- and dihalomethanes

A primary route of metabolism of dihalomethanes occurs via glutathione (GSH) transferase-catalyzed conjugation. Mammalian theta class GSH transferases and a group of bacterial dichloromethane dehalogenases are able to catalyze the hydrolytic dehalogenation of dihalomethanes via GSH conjugation and subsequent formation of HCHO. Dihalomethanes have been shown to induce revertants in Salmonella typhimurium TA 1535 expressing theta class GSH transferases. Two mammalian theta class GSH transferases (rat GST 5-5 and human GST T1) and the bacterial dehalogenase DM11 were compared in the in vitro conjugation of CH3Cl and using in vitro assays (HCHO formation) and the S. typhimurium mutagenesis assay with the dihalomethanes CH2Cl2, CH2Br2, CH2BrCl, CH2ICl, CH2I2, and CH2ClF. GSTs 5-5 and TI had similar characteristics and exhibited first-order rather than Michaelis-Menten kinetics for HCHO formation over the range of dihalomethane concentrations tested. In contrast, the DM11 enzyme displayed typical hyperbolic Michaelis-Menten kinetics for all of the compounds tested. A similar pattern was observed for the conjugation of CH3Cl The reversion tests with S. typhimurium expressing DM11 or GST 5-5 showed a concentration-dependent increase in revertants for most of the dihalomethanes, and DM11 produced revertants at dihalomethane concentrations lower than GST 5-5. Collectively, the results indicate that rates of conversion of dihalomethanes to HCHO are not correlated with mutagenicity and that GSH conjugates are genotoxic. The results are compared with the conjugation and genotoxicity of haloethanes in the preceding paper in this issue [Wheeler, J. B., Stourman, N. V., Armstrong, R. N., and Guengerich, F. P. (2001) Chem. Res. Toxicol. 14, 1107-1117]. The halide order appears most important in the dihalomethane conjugation reactions catalyzed by GST 5-5 and less so in GST T1 and DM11, probably due to changes in the rate-limiting steps

Results of an Aeroelastically Tailored Wing on the FLEXOP Demonstrator Aircraft

The idea of the EU funded FLEXOP project is to raise efficiency of a currently existing wing by derivative solution with higher aspect ratio at no excess structural weight. In order to enable such a resulting highly flexible wing the project goal is to develop methods for active suppression of flutter and passive load alleviation. The developed methods will be tested and validated with a UAV flutter demonstrator. The demonstrator is a 7m wingspan, 65kg MTOW UAV equipped with a jet engine. It features three different wing pairs. The first wing is a stiff design reference case, which is flown to get the baseline measurements for comparison. The second one is a wing designed very flexible specifically for active flutter control. The third wing is aeroelastically tailored for gust load alleviation. The paper describes the results of the aeroelastically tailored wing compared to the baseline reference wing

Ground Testing of the FLEXOP Demonstrator Aircraft

Ground testing campaign conducted on the FLEXOP demonstrator aircraft is presented in this paper. The conducted tests are grouped in structural, flight system and integration tests. Along with the description of the test setup and test execution, the main findings and conclusions are also given. The structural tests comprise the static, ground vibration and the airworthiness test. The static and the ground vibration tests were used for structural characterisation of the manufactured wings and airframe as a whole. Assessment and calibration of the Fibre Brag strain sensing system for wing shape and load reconstruction is also presented within this context. The airworthiness test is used to demonstrate the structural integrity of the manufactured wings under specified limit loads. Within the context of the flight system tests, the main components of the on-board autopilot hardware-software system are briefly introduced including the signal data flow from the RC transmitter to the aircraft controls, the functionality of the baseline autopilot software and the communication with the ground station. All of these components are integrated into the hardware-in-the-loop environment, which is also briefly introduced along with the servo motor identification and the hardware delay measurements. The measured hardware delay was considered in the design of the baseline and flutter controllers. The flutter controllers were tested together with the baseline controller in the software-in-the-loop environment. System integration tests are presented last. In this context the airbrake, the engine, the compatibility of electronic components, the range and the taxi tests are presented.Aerospace Structures & Computational Mechanic