Weather Hazards

Low-Level Wind Shear

Image sourced from Menkor Aviation (n.d.)

Winds can be an aircraft's greatest ally, yet also be its greatest nemesis. Have you ever felt like you were on a rocky boat while on board an aircraft prior to landing or during take-off? If you have, what you experienced was a low-level wind shear. According to the FAA (n.d.-a), low-level wind shear are abrupt winds that changes in speed and direction causing the aircraft to experience severe updrafts and downdrafts. In essence, it would feel like a piece of feather being thrown about by the wind in all directions.

How Do They Come About?

Low-level wind shear happens usually when there is a cold front, when there is a thunderstorm, areas of temperature inversions, or strong upper level winds that are more than 25 knots (FAA, n.d.-a). To add on, it can also be produced by heavy rains from severe thunderstorms which induces downbursts whereby the rain and rain-cooled air drops generate localized vortices which generates wind shear (National Weather Service, n.d.).

Why Is It Dangerous?

Low-level wind shear, especially microburst is the worst form of wind shear that can occur to an aircraft which is indicative from a ring of blowing dust or a severe rain shaft at the surface (FAA, n.d.-a). Generally, a microburst has a horizontal span of 1-2 miles and 1000 ft in height which can generate downdrafts of 6000 ft/min which leads to headwind losses of 30-90 knots (FAA, n.d.-a). All these will severely impact aircraft operations as the low-level wind shear causes turbulence and dangerous abrupt wind speed and direction changes. When instances as such occurs during critical phases in flight such as during landing and take-offs, it could be extremely dangerous which may even lead to dire consequences. Reason being, low-level wind shear will subject the aircraft to inadvertent lifts and descents (National Weather Service, n.d.) that can lead to crashes due to impediment of controls and manoeuvrability.

Image sourced from FAA (n.d.-b)

References

FAA. (n.d.-a). Chapter 12 - weather theory. https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/phak/14_phak_ch12.pdf

FAA. (n.d.-b). Downdraft [Illustration]. FAA. https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/phak/14_phak_ch12.pdf

Menkor Aviation. (n.d.). Windshear [Photograph]. Menkor Aviation. https://www.menkoraviation.com/en/safety/what-is-windshear-and-how-to-avoid-it/

National Weather Service. (n.d.). safety_thunderstorms. https://www.weather.gov/zme/safety_ts


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