Computer simulations, initial flight tests on a German Army CH-53G with "manual" pitch links and full-scale wind tunnel tests of a UH-60A rotor were conducted in order to investigate the capabilities of In-Flight Tuning to (a) reduce RT&B check flight time and (b) improve the 1/rev vibration level compared to what is achievable by today's RT&B process. It was demonstrated that active pitch links were able to compensate considerable inherent or simulated bladeto- blade dissimilarities. Moreover, the algorithms used were shown to be convergent and stable. Based on the results presented in this paper the following conclusions can be drawn: 1. The proposed architecture of an In-Flight Tuning System which solely uses adjustable pitch links is feasible to compensate unbalances resulting from mass and/or aerodynamic/geometric dissimilarities between the different blades; 2. With in-flight adjustable pitch links the 1/rev vibration level can be reduced in most cases far below the levels accepted today from the fixed RT&B compromise settings which stay unchanged throughout the whole flight envelope; 3. Optimum 1/rev vibration levels at different flight conditions cannot be achieved with a fixed set of pitch link lengths; the capability of an in-flight adjustment is crucial to achieve this goal; 4. Flat track is not a necessary or useful (pre)condition anymore to achieve minimum 1/rev vibrations; 5. The proposed In-Flight Tuning system is able to compensate for slowly increasing 1/rev vibrations resulting from external factors as water ingress, erosion or the like during operation of the aircraft. Hence, the number of dedicated RT&B procedures/flights can be reduced and the vibration level be kept at a low level. 6. The number of repetitive check flights with manual adjustments between the flights as used in today's RT&B procedures can be reduced to a single flight due to the in-flight adjustment functionality. The final prove of concept shall be achieved by the upcoming flight test campaign. Smart Pitch Rods will be fitted to a CH-53G helicopter and allow to validate not only the expected benefits but also to explore important operational aspects.
In-flight tuning: Wind tunnel test results and flight test preparation
Abstimmung während des Fluges: Windkanal-Versuchsergebnisse und Flugversuchsvorbereitungen
2011
12 Seiten, 22 Bilder, 1 Tabelle, 9 Quellen
Aufsatz (Konferenz)
Englisch
In-Flight Tuning: Wind Tunnel Test Results and Flight Test Preparation
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