In regards to low level wind shear, which of the following is true?

• A. Increase in headwind or decrease in tailwind will result in decreased IAS
• B. Decrease in headwind or increase in tailwind will result in increased IAS
• C. Decrease in headwind or increase in tailwind will result in decreased IAS
• D. None of the above

Answer: (C)

Low level wind shear affects the airspeed indicator because indicated airspeed is driven by the dynamic pressure caused by the wind hitting the pitot tube. When the headwind component decreases, the relative wind over the pitot tube weakens, so the dynamic pressure drops and the IAS falls. Similarly, if the tailwind component increases, the aircraft meets less headwind and the dynamic pressure over the sensor also drops, leading to a lower IAS. Therefore, a decrease in headwind or an increase in tailwind will cause a decrease in indicated airspeed. This is why that option is true and the others, which describe the opposite effects, aren’t correct.