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Low level windshear in approach. Positive versus Negative

- October 18, 2017

Low-level windshear is a sudden change in wind speed or direction. It can be in the horizontal plane, the most common one, or in the vertical plane, in which you will deal with a change in height. It can be associated with frontal masses, thunderstorms, low-level mountain waves (as usually found in islands) or mechanical turbulence. We can distinguish two different types of low-level windshear in the horizontal axis. Positive wind shear and negative wind shear. Let's explain the difference between them both. Disclaimer: Actions that we need to take in windshear situations are very well described in the FCOM of all Companies. Usually when we find an alert, you need to go around. But what happens if we don't find the alert? Positive windshear is a sudden increase in headwind, making the airspeed rise and making the aircraft fly above the glide slope. If you are told to expect positive windshear on final, you should land with a lower setting of flaps, so a