Helicopter flight characteristics in icing conditions

International Journal of Aerospace Engineering

2021

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Sustained flight operation in the rain conditions is still a challenge to a pilot. This problem can be mainly attributed to the aerodynamic performance degradation of aircraft. In this article, in order to quickly understand the influence of rainfall aiming at the engineering application, an approach to predict helicopter rotor performance degradation in heavy rain encounters is presented. Firstly, we develop a computational fluid dynamics- (CFD-) based method of simulation of the blade airfoil under natural rain scenario and different angles of attack in order to obtain a data-driven basis relating to multiple working conditions of the rotating blades for further analysis. Then, these data are studied using a discretization analysis method of rotor aerodynamics. CFD simulations are conducted, including the case of NACA 0012 airfoil with 10 m chord length, and the case of SC1095 airfoil used in a full-scale rotor of UH-60A helicopter. Prediction of helicopter rotor performance degradation is carried out in a thunderstorm heavy rain with the rain rate of 1500 mm/h using this full-scale rotor. The quantitative results indicate that heavy rain dramatically degrades the rotor performance. The maximum percentage decrease in lift coefficient of this full-scale rotor blade airfoil is reached by 12.75%. The maximum percentage increase in drag coefficient of this full-scale rotor blade airfoil is reached by 26.51%. The maximum percentage decrease in averaging lift-to-drag ratio of this full-scale rotor disk is reached by 26.39%.

Section: Discretization Analysis Methodmentioning

confidence: 99%

Numerical Simulation of Helicopter Rotor Performance Degradation in Natural Rain Encounter

International Journal of Aerospace Engineering

2021

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“…Previous icing study works on helicopter 11 have mainly involved introducing the icing-related increments of rotor thrust, side force, horizontal force, torque coefficients, and icing-related increment changes in the coning of the rotor flapping and in the first-order longitudinal/lateral flapping coefficients into the uniced flight dynamic model. In this section, using the above basic helicopter trim model, the non-uniform distribution of the angle of attack and Mach number of the rotor disk, based on the helicopter vortex theory, can be calculated.…”

Section: Methodsmentioning

confidence: 99%

“…5 and Flemming and Lednicer 6 initially studied helicopter icing problems. Recently, Cao and other researchers 4,7–12 investigated the icing problems that both covers theoretical insight into the mechanism of ice accretion and performance degradation prediction of aerodynamic and flight dynamic characteristics due to ice accretion. Flemming and Luszcz 13 first integrated the rotor ice accretion into a flight simulator.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Airflow hazard prediction for helicopter flight in icing condition

Proceedings of the Institution of Mechanical Engineers, Part G:

Sheridan

2012

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A methodology to predict the airflow hazard of helicopter flight in icing conditions is developed. By incorporating the existent ice accretion codes into an established basic helicopter flight dynamic model and considering airflow disturbance that mainly covers downdraft, head/tail wind, and left/right wind, the hazardous effects on trims, stability, and controllability of UH-60A single rotor helicopter in icing/ice-free conditions and within/without different types of wind field are investigated. The stability and controllability of helicopter that encounters airflow disturbance from wind velocity of 0 to 2.5–5.0 m/s for forward flight are examined. The indications of all the work are summarized at the end of this article. Furthermore, this method can be used to helicopter inflight safety prediction or airflow hazard avoidance analysis in icing conditions. It can also be laid as the foundation of the further research about the more complex airflow hazard prediction in icing conditions for helicopter flight safety.

“…As for the application of the coupled free-wake/panel method to helicopter flight dynamics model, the primary problem is how to realize the integration between the coupled free-wake/panel method and trim calculation. In the calculation procedure, initial trim computation can be conducted by using rotor vortex theory, in which the corresponding trim results and comparison with test data were shown by Cao et al 20 Then, based on those initial trim results, with the iterative solution of coupled free-wake/ panel method, the convergent wake geometry and fuselage panel strength were obtained, and by calculating the distribution of rotor plane induced velocity, the rotor aerodynamic force and torque can be obtained. Through solving the convergent rotor wake geometry with free-wake analytic technique, the rotor downwash influence on the center of pressure of fuselage, empennage and tail rotor can be computed.…”

Section: Trim In Level Flightmentioning

confidence: 99%

A coupled free-wake/panel method for rotor/fuselage/empennage aerodynamic interaction and helicopter trims

Proceedings of the Institution of Mechanical Engineers, Part G:

2014

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A coupled free-wake/panel method to predict the rotor downwash aerodynamic interaction and helicopter trims is presented. Free-wake method was developed to analyze aerodynamics interference of rotor wake, based on lifting-surface theory and vortex method, which relates the core radius, span station, and circulation of initial tip vortex with the blade-bound circulation distribution, and eliminates the empirical parameters during rotor free wake analysis. Helicopter fuselage with empennage was discretized into source panels. The vortex line mirror method was adopted to account for wake acceleration phenomenon that resulted from the close interaction between rotor wake and fuselage surface. The rotor wake geometry and downwash simulations were investigated including comparisons with the available measured data. Combined with the helicopter flight dynamics model and embedded in the trim procedure, the free-wake/panel coupled method was applied to calculate the rotor wake and its interference on other components of a full-scale UH-60A rotorcraft in level flight. Comparisons among predictions, referenced results, and experimental results are made for rotor wake geometries, blade-bound vortex, blade tip vortex, rotor downwash velocity, and control stick positions, and encouraging results were obtained. To validate the present method, this paper discusses the fundamental formulation, the numerical algorithms, and the simulation results.