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对某运输飞机在大襟翼偏度下的非常态俯仰振荡原因进行了分析。研究结果表明,该运输飞机在大襟翼偏度下飞行时因平尾受机翼的强下洗作用导致平尾下翼面发生局部分离,该分离未达到失速分离,从而引起飞机非常态的俯仰振荡。分离的主要原因是机身与平尾融合处抗流场逆压梯度能力下降,导致在大襟翼偏度飞行时出现局部分离,使得飞机出现纵向非常态俯仰振荡。该结论在风洞试验及该运输飞机试飞中得到验证。
The reasons for the abnormal pitching oscillations of a transport aircraft under large flap deflection are analyzed. The results show that when the airplane is flown under the large flap deviation, the tail plane of the tail plane is locally separated due to the strong lower wash of the tail at the tail end. The separation does not reach the stall separation, which leads to the non-normal pitching oscillation of the aircraft. The main reason for the separation is the decrease of the anti-pressure gradient capability of the fuselage and the flat tail in the confluence, resulting in the partial separation of the large-wing deviation flight and the longitudinal pitching of the aircraft. This conclusion is validated in the wind tunnel test and the test flight of the transport aircraft.