ISBN 9783843951401

978-3-8439-5140-1, Reihe Ingenieurwissenschaften

Jakob Thiemeier
Trim Condition Impact on Efficiency and Flight Mechanics of a Compound Helicopter in Cruise Flight

163 Seiten, Dissertation Universität Stuttgart (2022), Softcover, A5

Zusammenfassung / Abstract

In this thesis, the opportunity is numerically explored to operate the configuration of the compound helicopter Airbus Helicopters RACER with different trim strategies for a given 175 kts cruise flight condition at high advance ratio, utilizing its additional control degrees of freedom compared to conventional helicopters. Single trim parameters are varied within these trim strategies in order to investigate the impact of different trims on vehicle efficiency and flight mechanics. A high-fidelity simulation framework consisting of the structured flow solver FLOWer weakly coupled to the comprehensive analysis HOST is applied to capture the complex phenomena by which the unconventional configuration of RACER is characterized. The results obtained by this coupled framework are compared to the stand-alone comprehensive analysis, aiming at extending the knowledge of the agreement and the discrepancy between both approaches.

For the alteration of the trim condition, ten different free-flight trim laws with either eight or nine degrees of freedom were designed, aiming at a preferably isolated variation of the following flight-mechanical quantities: (1) main rotor lift share, (2) main rotor propulsion, (3) longitudinal lift offset, (4) lateral lift offset, (5) airframe anti-torque share and (6) rotational speed of the rotors. As a result, three major domains of deviations between comprehensive analysis and CFD are identified: the main rotor, the lateral rotors, and the polars of wing flaps, elevator and rudder.