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August 17, 2010 / Dave Gorham

B737 Crashes in Columbia…Is Lightning to Blame?

Is lightning to blame for the Columbian plane crash early Monday? Well there are a few internet sources reporting lightning as the cause, but with my aviation weather knowledge I’d say there’s more than likely other factors involved as aircraft these days are engineered with lightning protection. Planes now have to go through extensive lightning certification tests in order to verify the safety of their designs. In fact, the last confirmed civilian plane crash due to lightning in the U.S. was in 1967, when lightning caused a catastrophic fuel tank explosion.

A Boeing 737 split apart after crashing early Monday morning on San Andres Island, Columbia. Image: AP

The B737 Jetliner Aries was landing shortly after midnight during a thunderstorm Monday morning when it crashed just short of the runway. Since the plane was landing during a thunderstorm it’s possible it could have been caught up in the downdraft, which is generated when rain-cooled, denser air sinks inside a thunderstorm. The downdraft is intensified by evaporative cooling as drier air from the edges of the storm mix with the moist air within the storm. These processes lead to a rapid downward rush of air. Downbursts can create hazardous conditions for pilots.

Take a look at the image below, courtesy of the National Weather Service.
1. As an aircraft descends into the airport they follow an imagery line called the “glide slope” to the runway.
2. Upon entering the downburst, the plane encounters a headwind, which is an increase in wind speed over the aircraft. The faster wind creates lift causing the plane to rise above the glide slope. To return the plane to the proper position, the pilot lowers the throttle to decrease the plane’s speed thereby causing the plane to descend.
3. As the plane flies to the other side of the downburst, the wind direction shifts and is now from behind the aircraft. This decreases the wind over the wing reducing lift. The plane sinks below the glide slope.
4. However, the tailwind remains strong and even with the pilot applying full throttle trying to increase lift again, there is little, if any, room to recover from the rapid descent causing the plane to crash short of the runway.
Monday’s crash in Columbia occurred about 260 feet (80 meters) short of the runway and when it crashed the plane split apart.

Downbursts can create hazardous conditions for pilots. Image: NWS

Other weather factors that may have been involved could have been the reduced visibilities in rain the pilot encountered or perhaps even low-level wind shear. Actually, Meteorologist Dave Gorham wrote a blog earlier this month detailing what low-level wind shear is and the role it played in the Delta Flight 191 crash in Dallas 25-years ago. Check it out here. http://yourweatherblog.com/2010/08/delta-flight-191-25-years-later/

On Monday, a total of 131 people were on board the plane when it crashed on the island of San Andres, Colombia. It’s unfortunate that one person lost her life in the crash, but it definitely could have been a lot worse, especially when you look at what’s left of the aircraft. The plane had taken off from Bogota around midnight on Sunday.

San Andres is located 90 miles off the eastern coastline of Nicaragua. Image: http://www.worldatlas.com

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