Over the years tornadoes have wrecked numerous aircraft on the ground, but few are known to have hit aircraft in the air.
A pilot in an airplane hit by a tornado on the ground is in great danger, as shown by the story of one such pilot reported in the Florida Times-Union in Jacksonville on June 20, 1998:
"Answering prayers for rain with a vengeful force, a wall of storms crossing Northeast Florida last night spawned tornado-like winds and damaged planes at Jacksonville International Airport. The tornado 'was your classic Wizard of Oz tornado,' said Jim White, a forestry pilot for the Georgia Forestry Commission who sat inside his airplane [the story doesn't say what kind] as winds flipped it over several times. 'I don't know how many times it flipped. The first thing I saw is the landing gear flipping around,' he said. 'I believe the aircraft is totally destroyed. I feel great. I thought I was going to die.'"
The story's reference to "tornado-like" winds illustrates the confusion that thunderstorm winds can leave in their wake. People often assume that any wind that blows the roofs off buildings or rips airplanes from their tiedowns is a tornado. But thunderstorms also produce strong straight-line winds from downbursts.
What's the difference?
Downburst winds blast more or less straight down from a thunderstorm and spread out when they hit the ground, sometimes with speeds faster than 100 mph. That's enough to rip airplanes from their tiedowns.
A tornado is a spinning whirl of wind extending up into a cloud - usually a cumulonimbus (thunderstorm) cloud. That wind, unlike a downburst, is rising as it spins. The part of the tornado that we see between the bottom of the cloud and the ground is a mixture of cloud, dust, dirt, and debris. Strong winds that we don't see can be spinning around and rising outside the visible tornado.
White's reference in the Florida Times-Union story to a "classic Wizard of Oz tornado" indicates that his plane was tossed around by a twister, not a downburst.
One reason that few pilots have tangled with tornadoes is that a tornado and the thunderstorms that produce strong tornadoes are obviously nasty. Your natural survival instincts, not weather knowledge, should tell you to stay far away from anything that looks like conditions depicted in the photo.
The trouble is that many tornadoes don't look like the one in the photo, which was taken on the Plains near Cornell, Oklahoma, where trees and haze aren't as likely to hide a tornado as in the Southeast. By the way, many parts of the Southeast average as many tornadoes per square mile as the Great Plains, which is often called Tornado Alley.
Even on the Plains where the visibility is usually better than in the Southeast, heavy rain or maybe hail can hide a tornado since they often form on the boundary where air is rising into a thunderstorm and where it is descending. Rain or hail often is falling there as well.
In his history of tor-nadoes and tornado science, The Tornado: Nature's Ultimate Windstorm, Thomas Grazulis briefly describes two fatal airplane crashes that involved tornadoes.
The worst was on October 6, 1981, when a Fokker F-28 airliner crashed after losing a wing about 25 miles south of Rotterdam, the Netherlands. A policeman photographed the tornado and the smoke from the crashed airplane, Grazulis writes. An investigation concluded that the airplane flew into "the tornado circulation, in cloud, shortly after the tornado funnel had lifted from the ground."
Grazulis also writes about a Mooney M20E that crashed near Ottawa, Kansas, killing all three aboard, at about the same time that a tornado killed two people approximately a mile from the crash site. "What happened to the veteran pilot and his two passengers in the last minute will always be a mystery," Grazulis writes. In its report on the crash the National Transportation Safety Board does not mention the tornado but refers to two people being killed by "severe weather" one-third of a mile from where the airplane crashed.
No one can say whether the airplanes actually flew into a tornado in either of these cases, but this is almost beside the point, Grazulis says. "All matter of strange occurrences are going on around tornadoes" with the most dangerous winds around a tornado concentrated near the surface. For instance, "There is all kinds of stuff that will blow your windows out."
Despite the danger, a few pilots have flown close to tornadoes on research missions.
One of these was Stirling Colgate, an astrophysicist from the Los Alamos National Laboratory, who wanted to test theories about the role of electricity in tornadoes by firing small, homemade, instrumented rockets into tornadoes from a Cessna 210. The Tornado Classics videotape that Grazulis' Tornado Project sells includes scenes that Colgate took with a movie camera as he tried to fire rockets into a tornado over Oklahoma in May 1981. That flight was smooth even relatively close to the tornado, but in the movie footage we see the rockets fired from the Cessna 210 miss the tornado.
Keay Davidson tells the story of Colgate's airborne tornado research in the book Twister: The Science of Tornadoes and the Making of an Adventure Movie. In May 1982 he was trying to fly small rockets into another tornado near Pampa, Texas, when a downdraft sent the airplane toward the ground, Davidson writes. He regained control just short of hitting the ground. He flew on and fired two or three rockets at a tornado, but on his way back to the airport "a furious thunderstorm pummelled the plane. Colgate made an emergency landing in a field," Davidson writes. "He was shaken and upset. He would never chase another tornado."
Over the past two decades researchers have learned a huge amount about tornadoes and the thunderstorms that spawn them, mostly from measurements captured by teams of scientific storm-chasers who deploy weather instruments on the ground and on balloons launched into storms, from still and video cameras, and even a Doppler radar mounted on a truck.
Much remains to be learned, however, and some researchers believe that aircraft offer the best way to gather the data they need. These researchers use unmanned aircraft, including some variations of radio-controlled model aircraft.
Sage advice for all pilots, including those with a passion for meteorology, is summed up by a quotation in Davidson's book from a pilot involved in tornado research: "The best practice for flying through tornadoes is flying through mountains."
The Tornado Rating Scale
Using after-the-fact damage surveys, the National Weather Service classifies tornadoes on an F-0 to F-5 scale developed by the late tornado researcher T. Theodore Fujita of the University of Chicago.
F-0 Light damage. Wind up to 72 mph.
F-1 Moderate damage. Wind 73 to 112 mph.
F-2 Considerable damage. Wind 113 to 157 mph.
F-3 Severe damage. Wind 158 to 206 mph.
F-4 Devastating damage. Wind 207 to 260 mph.
F-5 Incredible damage. Wind above 261 mph.
F-0 and F-1 tornadoes are considered "weak"; F-2 and F-3 are "strong," while F-4 and F-5 are "violent."
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