Micro Bursts and Wind Shear

 

    The wind has a great impact on aircraft performance. A headwind increases lift and drag and a tailwind does the opposite. A microburst occurs from convective precipitation falling into dry air causing a starburst shape of wind directions centered around a downdraft point illustrated in the picture above. This drastic change in wind velocity and direction is referred to as wind shear (FAA, n.d.).

Wind shear can occur at any altitude but wind shear at low altitude is especially hazardous due to the proximity of the aircraft to the ground. When an aircraft flies through a microburst after departure, the aircraft will experience increased lift from the headwind causing the pilot to nose down or decrease throttle to maintain their departure path. In the center of the microburst, the downdraft changes the wind direction from a headwind to a vertical downwind. This decreases the lift generated by the wings and increases the "weight". The aircraft will lose altitude causing the pilot to increase thrust and nose the aircraft up to attempt to maintain altitude. On the backside of a microburst, the aircraft will experience a tailwind further decreasing the lift generated by the wings causing another loss of altitude. The pilot will increase the throttle and lift the nose, even more, to attempt to increase lift. The loss of altitude during a departure increases the risk of the aircraft not gaining enough altitude to clear potential obstacles and can result in a collision (FAA, n.d.). 

    

    During landing, microbursts have a similar effect. The sudden change in wind direction causes the aircraft to lose altitude. In a worst-case scenario, the aircraft will land/crash short of the runway. The constant change in power and attitude could also cause the aircraft to land long and overshoot the landing with increased power potential leading to the aircraft not being able to stop prior to the end of the runway (FAA, n.d.).

References

Federal Aviation Administration. Weather Therory. (n.d.). Retrieved August 30, 2022, from https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/phak/14_phak_ch12.pdf