The Plane and The Wind
Observe the three planes in the animation below. Each plane isheading south with a speed of 100 mi/hr. Each plane flies amidst a wind which blows at 20 mi/hr. In the first case, the plane encounters a tailwind (from behind) of 20 mi/hr. The combined effect of the tailwind and the plane speed provide a resultant velocity of 120 mi/hr. In the second case, the plane encounters a headwind (from the front) of 20 mi/hr. The combined effect of the headwind and the plane speed provide a resultant velocity of 80 mi/hr. In the third case, the plane encounters a crosswind (from the side) of 20 mi/hr. The combined effect of the headwind and the plane speed provide a resultant velocity of 102 mi/hr (directed at an 11.3 degree angle east of south). These three resultant velocities can be determined using simple rules of vector addition. In the case of the crosswind, the Pythagorean Theorem and SOH CAH TOA are utilized to determine the magnitude and the direction of the resultant velocity
Effects on flight
Glider ground launch due to wind shear.
In gliding, wind gradients just above the surface affect the takeoff and landing phases of flight of a glider. Wind gradient can have a noticeable effect on ground launches, also known as winch launches or wire launches. If the wind gradient is significant or sudden, or both, and the pilot maintains the same pitch attitude, the indicated airspeed will increase, possibly exceeding the maximum ground launch tow speed. The pilot must adjust the airspeed to deal with the effect of the gradient
When landing, wind shear is also a hazard, particularly when the winds are strong. As the glider descends through the wind gradient on final approach to landing, airspeed decreases while sink rate increases, and there is insufficient time to accelerate prior to ground contact. The pilot must anticipate the wind gradient and use a higher approach speed to compensate for it.[
Wind shear is also a hazard for aircraft making steep turns near the ground. It is a particular problem for gliders which have a relatively long wingspan, which exposes them to a greater wind speed difference for a given bank angle. The different airspeed experienced by each wing tip can result in an aerodynamic stall on one wing, causing a loss of control accident]
ليست هناك تعليقات:
إرسال تعليق