飛機受低空風切干擾下之橫向空氣動力特性與穩定控制研究

Aircraft Lateral Aerodynamics, Stability and Control Study under a Low Level Wind Shear Situation

王穎駿(Y. C. Wang) ； 陸鵬舉(P. J. Lu) ； 宛同(T. Wan)

《中國航空太空學會學刊》 33卷3期 (2001/09) Pp. 201-208

https://doi.org/10.6124/TAASRC.200109_33(3).08

摘要

風切(Wind-Shear)是氣象對飛行安全最大的影響因素之一，尤以發生在低空的低空風切對進揚、離場航機影響爲最。本文是繼縱向問題後，進一步研究飛機在低空風切中橫向(側向)方面的空氣動力特性及穩定度問題。在平有風切流場(Parallel Shear Flow)下，藉由風洞中波音七四七模型機實驗所量測到的側向空氣動力導數，來得到側向穩定度分析所需的穩定導數(Stability Derivatives)。本研究顯示，在平行風切狀況下，橫向空氣動力係數隨風切強度不同而改變，尤以對飛機的盤旋模態(Spiral Mode)影響爲甚－產生不穩定現象，證明了在有縱向風速梯度的風切狀況，依然對側向穩定有不良影響。此外，經由迴授控制理論－增穩系統，(Stability Augmentation system)的設計，採用“極點指示法”(Pole Assignment Method)找出合適之迴授增益，對於風切中之側向不穩定性有所改善，因此對飛行品質的提高及飛航安全的助益，將有正面作用。

關鍵字

低空風切 ； 側向穩定 ； 盤旋模態 ； 增穩系統 ； 極點指示法

並列摘要

The lateral aerodynamic and stability properties of Boeing 747 civil transport subject to wind-shear effect were studied. Parallel shear wind was produced in a low-speed wind tunnel by the use of tapered honeycombs to retard the oncoming stream, resulting in a linear velocity shear in the transverse direction. In the present analysis, the steady-state aerodynamic derivatives were obtained from the shear flow wind tunnel measurements, while the unsteady derivatives associated with the rate changes of pitch, yaw and roll angles were borrowed from the uniform flow results. It has been shown in the present research that the vertical wind shear can influence the lateral aerodynamic characteristics and hence the aircraft's lateral stabilities. As the wind shear effect increases, the spiral mode was found to be unstable in an exponentially growing manner. In order to stabilize this lateral instability induced by wind shear, a stability augmentation system using pole assignment technique of the feedback control theory was developed. The spiral instability was shown to be stabilized as the control gain was redefined.

並列關鍵字

Low-Level Wind Shear ； Lateral Stability ； Spiral Mode ； Stability Augmentation System ； Pole Assigment Method