Sunday, 01 March 2009 05:51
Hi Capt Lim,
Your website is so wonderful. May I ask what a microburst is?
Thank you for your reply.
A microburst is very different from a tornado in that it is much localized in nature. It arises from a column of sinking air and producing divergent and straight line winds at the surface of the earth. On the other hand, the sinking air from the tornadoes is generally convergent.
There are two types of microburst: wet and dry microburst. They go through three stages in their life cycle: the outburst, downburst, and cushion stages. The scale and suddenness of a microburst makes it a great danger to aircraft due to the low-level wind shear caused by its gust front, with several fatal crashes attributed to the phenomenon over the past several decades.
A microburst often causes aircraft to crash when they are attempting to land. The microburst is an extremely powerful gust of air that, once hitting the ground, spreads in all directions. As the aircraft is coming in to land, the pilots try to slow the plane to an appropriate speed. When the microburst hits, the pilots will see a large increase in their airspeed, caused by the force of the headwind created by the microburst.
A pilot inexperienced with microburst would try to decrease the speed. The plane would then travel through the microburst, and fly into the tailwind, causing a sudden decrease in the amount of air flowing across the wings. The decrease in airflow over the wings of the aircraft causes a drop in the amount of lift produced. This decrease in lift combined with a strong downward flow of air can cause the thrust required to remain at altitude to exceed what is available.
Amongst the other possible causes, it appears that the Turkish Airlines Boeing 737-800 plane crash at the Schiphol Airport, Amsterdam on 25 February 2009 has the symptoms of an accident caused by a microburst. This is only a speculation but investigation is on-going.