(KXAN) — Aviation is possible through an understanding of physics and engineering, allowing humans to overcome gravity and travel great distances in ways that would have been only a dream for most of our history.
However, natural phenomena can interfere with aviation; one such phenomenon is turbulence, an atmospheric phenomenon that causes chaotic changes in pitch, roll, and yaw. Recently, as a result of the turbulence, seven passengers were injured Lufthansa flight from Texas to Germanyas well as the fatal injury of a passenger on a separate plane over New England just days later.
The The Federal Aviation Administration recommends passengers remain seated during flights with seat belts fastened to protect against unexpected turbulence. According to the agency, between 2009 and 2021, turbulence caused injuries to at least 146 people.
How is turbulence formed?
According to the National Meteorological Service, there is four causes of turbulence: mechanical, thermal, pressure fronts and wind shear. The effects of turbulence are rated from mild (slight stress on protective restraints) to severe (may cause structural damage).
Mechanical turbulence is created by friction between the wind and obstacles on the ground. These obstacles (trees, mountains, buildings, etc.) obstruct the wind, creating eddies of air that move quickly downstream. Higher wind speed creates larger eddies and stronger turbulence.
Convection-induced thermal turbulence occurs below clouds and usually affects aircraft only during takeoff and landing. The hot earth causes the air to rise, cooling as it moves away from the heat, causing it to increase in density and consequently fall downward.
Frontal turbulence occurs when low and high pressure fronts collide — the warm air of a high pressure front rises above a cold front. This collision can also form thunderstorms; if so, the turbulence will be more severe.
Wind shear or changes in wind direction and/or speed can also cause turbulence. This can occur at much higher altitudes than the other three types, and can reach well above the flight ceiling of commercial aircraft.
This high-altitude wind shear occurs in the form of “slots” around jet streams, which are narrow bands of fast-moving air. This is called “clear air turbulence”.
Thunderstorms, according to the NWS, create strong vertical air currents that can “move an aircraft up or down vertically 2,000 to 6,000 feet.” This type of turbulence typically occurs at altitudes between 12,000 and 20,000 feet and up to 20 miles from the storm chamber.
Turbulence, still the leading cause of flight injuries, affects flight attendants far more than passengers.
A 2021 NTSB report found that between 2009 and 2018, there were 111 turbulence-related accidents that resulted in at least one serious injury. But flight attendants – who often lift and move – were the most frequently injured, accounting for 78.9% of those seriously injured.
Climate change is expected to worsen turbulence in the coming decades, experts say, although improved weather forecasting will help.
Sometimes, however, the weather events that cause turbulence are difficult to predict. 11 passengers on a Hawaiian Airlines flight between Phoenix and Honolulu in December were seriously injured amid unusually severe turbulence, which the NTSB later determined was caused by a cloud that vertically “raised” toward the plane, leaving no time for the crew to swerve or warn passengers.
Another “turbulence” in the skies above New England resulted in the death of a passenger on Friday, the NTSB said, although the nature of the passenger’s injuries was not disclosed.
The Associated Press contributed to this report.