Compound Helicopter X³ in High-Speed Flight: Correlation of Simulation and Flight Test

Abstract

This work presents the correlation of simulation results and flight-test data for a high-speed (V = 220 kt), high advance ratio (μ > 0.5) flight of the compound helicopter X³. The simulation tool chain consists of state-of-the-art coupling between the computational fluid dynamics (CFD) code FLOWer and the comprehensive analysis tool HOST. By applying a free-flight trim procedure, the experimental flight state is accurately represented in the simulation. The deviations of most trim controls is below 1°, and the maximum deviation is less than 1.4°. The analysis of the high-fidelity CFD results illustrates key features of the flow physics at this high advance ratio, such as wake interactions, reverse flow, and advancing side loading. The correlation of rotor dynamics data between simulation and flight test is favorable. Good accordance is demonstrated for flap bending moments, torsion moments, and pitch link loads. In contrast, the correlation is weaker for the chord bending moments for which it is shown that the interblade damper and drive train model mostly determine the structural loads.

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“…Therefore, to increase the maximum forward speed of a helicopter, the blade tip speed may have to be reduced to alleviate compressibility effects. For high speed compound helicopters [1][2][3], tip speed is usually reduced in high speed flight, and at a specified forward speed, the rotor will undergo a transient process of rotor speed transition.…”

Improved neural network adaptive control for compound helicopter with uncertain cross-coupling in multimodal maneuver

“…Recently, many literatures revealed complex aerodynamic characteristics of compound helicopters and made it possible to build an accurate compound helicopter nominal model which is helpful for control system design [7][8][9][10]. However, there are still few related research results to deal with the challenges in advanced controller design.…”

Improved Neural Network Adaptive Control for Compound Helicopter with Uncertain Cross-Coupling in Multimodal Maneuver

“…Recently, many literatures revealed complex aerodynamic characteristics of compound helicopters and made it possible to build an accurate compound helicopter nominal model which is helpful for control system design [7][8][9][10]. However, there are still few related research results to deal with the challenges in advanced controller design.…”