Khi quay cánh quạt, lực ly tâm được tạo ra mà kéo lưỡi ra ngoài từ các trung tâm. Khi thang máy (hoặc khí động lực) được tạo ra và kết hợp với lực ly tâm coning xảy ra (xem hình 3-11). Coning tăng lên khi tăng lên thang máy | HELICOPTER AERODYNAMICS WORKBOOK CHAPTER 3 CONING As the rotor blades turn centrifugal force is created which pulls the blades outward from the hub. When lift or aerodynamic force is created and combines with centrifugal force coning occurs see figure 3-11 . Coning increases as lift increases. Figure 3-11 VORTICES As the rotor blades rotate and lift is produced high pressure is formed below the blade and low pressure above the blade. The sharp trailing edge of the blade keeps the high-pressure air from the low-pressure area on most of the blade except for the tip where nothing prevents the air from curling up from the bottom of the blade to the top. This air continues to spiral and drops off to form the trailing tip vortex. This vortex continues to spin and the velocity drops off with increasing distance from the origin. In a hover the vortices of one revolution impinge on the vortices of the following revolutions causing an uneven path of the vortices which eventually destroy each other. These tip vortices affect the induced velocity through the rotor system and due to this impingement and resultant unsteadiness in the flow field a rotor system in a hover creates its own gusty air requiring the pilot to constantly correct to maintain a hover figure 3-12 . Figure 3-12 HELICOPTER POWERED FLIGHT ANALYSIS 3-11 CHAPTER 3 HELICOPTER AERODYNAMICS WORKBOOK To balance the tip vortices another vortex is formed at the blade root which writhes around erratically through and around the main rotor system. This root vortex has an equal and opposite effect on the tip vortex which the pilot must correct. This usually manifests itself in heading changes as the root vortex impinges on the tail rotor and generally occurs when within one rotor diameter of the ground. Main rotor vortices can also affect the tail rotor during specific wind conditions which are covered in the TH-57 NATOPS Manual. GROUND EFFECT While the helicopter is in a hover and in other flight conditions close to the
