It is not unusual for airline passengers to feel a sudden jolt during a flight. Often these turbulences are spontaneous, even when the weather conditions appear calm, an aircraft may be shaken to some extent or may even briefly lose altitude before returning to normal.
Such effects are sometimes attributed to an aircraft encountering an “air gap”, but is this accurate? Well, as it turns out, that’s not quite right, because air gaps don’t actually exist.
“Practically, there is no such thing. It appears to be a layman’s term to describe certain forms of turbulence or manifestations of wind,” said Guy Gratton, aeronautical engineer, test pilot and professor of aviation at Cranfield University in the UK. states Live Science.
“One of the most unpredictable of all weather phenomena that is significant to pilots,” the National Weather Service describes a turbulence. Airplanes experience turbulence when they come into contact with a “high-magnitude and relatively random current or an ascending or descending column of air,” Gratton added.
What is this phenomenon after all?
The term “wind shear” is used to describe a “sudden change” in wind speed. This instantaneous change in wind speed or direction occurs over a relatively short distance in the atmosphere and can occur at both high and low altitude.
“If an aircraft is flying at a constant speed and altitude, then the headwind suddenly reduces or enters a descending column of air, this can cause the aircraft to descend suddenly,” explained Gratton. “Conversely, if the headwind picks up quickly or the plane enters a column of rising air, this can cause it to climb suddenly.” So where is an airplane most likely to encounter such conditions?
“There are two main places,” Gratton said. “Either around a cumulonimbus cloud, which typically has large-magnitude air currents around it, or around the edges of one of the jet streams.” Jet streams are essentially rivers of wind rising in the atmosphere and have a huge influence on climate because they can push air masses around and affect weather patterns.
The influence of clouds
Cumulonimbus clouds are commonly referred to as “thunder clouds” because they are “the only type of cloud that can produce hail, thunder, and lightning.” They arise from convection, which is warm air that rises because it is less dense than the surrounding atmosphere and “exists throughout the height of the troposphere”, the lowest layer of the Earth’s atmosphere, which extends to about 10,000 meters above sea level .
Turbulence is relatively common around these clouds when updrafts and downdrafts converge. According to the Aviation Academy, an aviation resource website, “microbursts,” a term used to describe particularly dangerous extreme winds, can cause airplanes to experience “downdrafts in excess of 610 meters per minute and surface winds exceeding 185 kilometers per hour”.
It can certainly be a shock to be shaken when riding on a plane, and the experience can range from quite uncomfortable to downright scary. But can turbulence damage a ship? And if so, could it cause a plane to crash or require a pilot to make an emergency landing?
What are the risks to which an airplane is subjected?
“In an extreme situation, turbulence can damage an aircraft,” Gratton confirmed. “If the airplane suddenly goes into climb or descent and flies too fast for those conditions, the airplane can become overloaded. In simplistic terms, this could tear the wings off, with inevitably serious consequences.” Gratton noted that wind shear can also affect airplanes in different ways.
“An encounter with crosswinds, if close to the ground, can cause the aircraft to spin out of control with very serious consequences,” he said. However, Gratton is keen to note that these are worst-case scenarios and are highly unlikely to happen. “Any type of turbulence or shear accident is very rare. In fact, it should be nearly impossible because airports and aircraft have wind shear detection systems and pilots know to slow aircraft below critical speeds if such severe turbulence is predicted.
“In reality, the biggest risk may be from objects flying around the cabin that have not been properly secured, which can happen even when the crew is doing their job properly.”