关键词: 航空运输, 最优编队位置, 快速仿真计算模型, 尾涡流场, 编队飞行危险区域

Abstract: Formation flight is one of the important measures to realize the green development of civil aviation. Based on the analysis of the hazard area of the tail vortex of the lead aircraft, determining the optimal position of the trailing aircraft is the key to formation flight. Firstly, based on the Probabilistic Two-Phase Wake Vortex Decay, the evolution of the induced roll moment coefficient of the trailing aircraft was analyzed by using the Hallock-Burnham vortex model and the induced roll moment coefficient model. Then, based on the safety threshold, the wake vortex hazard area of the lead aircraft was calculated with considering the influence of flight altitude, speed, and wind on the hazard area. Finally, based on the fuel flow reduction rate at different positions of the trailing aircraft, the optimal position of the trailing aircraft in formation flight was obtained. The results show that the induced rolling moment coefficient is first increased, then decreased, and again increased with the increase of the transverse distance between the leading and trailing aircraft. With the increase of longitudinal distance, it decreased slowly first and then rapidly. The higher altitude leads to a lower speed and a higher peak value of the induced rolling moment coefficient, and thus the larger wake vortex hazard area of the lead aircraft. With the increase of the longitudinal distance, the hazard area is decreased continuously, and the altitude is decreased continuously with the sinking of the vortex core. The crosswind diverges thehazard area, and the greater crosswind leads to the greater deviation. A tailwind increases the longitudinal distance of the hazard area, while a headwind does the opposite. When two B737-800 aircraft fly in formation at 12000 m altitude at Mach 0.78, if the longitudinal spacing between lead and trailing aircraft is 3000 m, the optimal position of the trailing aircraft in no wind condition is the transverse spacing of 30 m or negative 30 meters and vertical spacing of 29 m, and the fuel flow reduction rate is 7.01%. Compared with the no wind condition, the fuel flow reduction rate and vertical distance remain the same under the left wind of 20 meters per second, while the lateral distance increases. At the downwind condition of 20 meters per second, the reduction rate of the fuel flow increases, the lateral distance remains unchanged, and the vertical distance decreases. At the headwind condition of 20 meters per second, the reduction rate of the fuel flow decreases, the lateral distance remains the same, and the vertical distance increases.

Key words: air transportation, optimal formation flight position, fast simulation calculation model, flow filed of wake vortex, formation flight hazard area