Editing Storm (section)

=== Aviation ===
[[File:Windshearaircraftnasa.gif|thumb|Effect of wind shear on aircraft trajectory.  Merely correcting for the initial gust front can have dire consequences.]]

Hail is one of the most significant thunderstorm hazards to aircraft.<ref>{{cite web|url=http://www.easa.europa.eu/safety-and-research/research-projects/docs/large-aeroplanes/EASA.2008_5.pdf |date=November 2010 |title=Hail Threat Standardisation |author1=P.R. Field |author2=W.H. Hand |author3=G. Cappelluti |publisher=European Aviation Safety Agency. RP EASA.2008/5 |display-authors=etal |url-status=dead |archive-url=https://web.archive.org/web/20131207052634/http://www.easa.europa.eu/safety-and-research/research-projects/docs/large-aeroplanes/EASA.2008_5.pdf |archive-date=2013-12-07 }}</ref> When hail stones exceed {{convert|0.5|in|mm}} in diameter, planes can be seriously damaged within seconds.<ref>{{cite web|url=http://www.aviationweather.ws/063_Hazards.php|title=Hazards|author=Federal Aviation Administration|year=2009|access-date=2009-08-29|author-link=Federal Aviation Administration}}</ref> The hailstones accumulating on the ground can also be hazardous to landing aircraft.  Strong wind outflow from thunderstorms causes rapid changes in the three-dimensional wind velocity just above ground level. Initially, this outflow causes a headwind that increases airspeed, which normally causes a pilot to reduce engine power if they are unaware of the wind shear. As the aircraft passes into the region of the downdraft, the localized headwind diminishes, reducing the aircraft's airspeed and increasing its sink rate. Then, when the aircraft passes through the other side of the downdraft, the headwind becomes a tailwind, reducing lift generated by the wings, and leaving the aircraft in a low-power, low-speed descent. This can lead to an accident if the aircraft is too low to effect a recovery before ground contact. As the result of the accidents in the 1970s and 1980s, in 1988 the U.S. [[Federal Aviation Administration]] mandated that all commercial aircraft have [[Airborne wind shear detection and alert system|on-board wind shear detection systems]] by 1993. Between 1964 and 1985, wind shear directly caused or contributed to 26 major civil transport aircraft accidents in the U.S. that led to 620 deaths and 200 injuries. Since 1995, the number of major civil aircraft accidents caused by wind shear has dropped to approximately one every ten years, due to the mandated on-board detection as well as the addition of Doppler [[weather radar]] units on the ground. ([[NEXRAD]])<ref>{{cite web|author=National Aeronautics and Space Administration, [[Langley Air Force Base]] |url=http://oea.larc.nasa.gov/PAIS/Windshear.html |title=Making the Skies Safer From Windshear |date=June 1992 |access-date=2006-10-22 |url-status=dead |archive-url=https://web.archive.org/web/20060823125528/http://oea.larc.nasa.gov/PAIS/Windshear.html |archive-date=2006-08-23 }}</ref>