What is turbulence and why is it getting worse?

About 11 hours after take-off in London, a Singapore Airlines flight hit severe turbulence on Tuesday, forcing the crew to make an emergency landing in Bangkok. One passenger died and dozens were injured during the incident. Last year, a Delta Air Lines flight from Milan was about 64km away from its destination in Atlanta when it hit severe turbulence. Although the Airbus 350 plane landed safely, 11 people were taken to hospital. A few days earlier, passengers on a flight over Mallorca in Spain were videoed screaming amid strong winds and storms. These incidents follow others this year during which severe turbulence has caused injuries . It also comes after the release of a report that found bumpier flights are more common than ever before, with clear-air turbulence intensifying significantly worldwide in the past four decades. “We’ve only been tracking turbulence since the 1970s,” Vance Hilderman, chief executive of aviation and safety-critical services company Afuzion, tells The National . “We know that temperatures generally declined in the century prior to that as part of normal global fluctuations. However, in the past 50 years, some temperatures have increased and assessed turbulence has correspondingly increased as expected.” “Turbulence is a common occurrence during flights and can vary from light to severe intensity,” explains Captain Michael Schreiber, chief of pilot technical operations at Emirates Airline . It refers to the irregular and often abrupt changes in the airflow that an aircraft experiences while flying through the atmosphere, he adds. “If happening, it normally results in sudden, erratic movements or vibrations of the aircraft.” There are various reasons why this might happen, he says. There’s clear-air turbulence , which occurs at high altitudes in otherwise clear skies and is often associated with the jet stream – fast-flowing air currents that move from west to east in the upper atmosphere. Then there’s convective turbulence, which comes from vertical air movement due to heating from the Earth’s surface, often associated with clouds and thunderstorms. Mechanical turbulence happens when air encounters obstacles such as mountains or buildings; while wake turbulence is generated by aircraft vortices – circular patterns of rotating air left behind a wing as it generates lift – or jetwash, which are gases expelled from the engine. “Remember, turbulence is caused by temperature differences and changes. The higher the altitude, the thinner and colder the air, and thus less turbulence. A cooling evening in an Arizona summer has maximum turbulence,” Mr Hilderman says. Mr Schreiber also says certain parts of the world and times of year are more prone to turbulent skies due to meteorological factors. “During the hot summer, for example, you may notice that during departure, approach and landing, the air you travel through is generally rougher than during the cooler winter season. This is caused by the air masses heated up by the hot surfaces and rising vertically.” “Like ocean waves, ship captains can mitigate ocean wave effects via manoeuvring, but cannot avoid waves,” says Mr Hilderman. “Aircraft can try to fly around turbulence, but turbulence is dynamically moving and changing and not readily detected.” Mr Schreiber, however, says Emirates is investing heavily in new technologies to make these predictions more accurate. The airline’s pilots also receive training on how to deal with it. “Practical training around turbulence avoidance and management is conducted in the flight simulator,” he says. “Pilots are instructed how to navigate around areas of turbulence and how to ensure the safety of our passengers and crew in cases where turbulence is encountered in-flight. “Improved technology, such as better weather prediction tools, support the pilots in making good decisions, avoiding areas of rough air while in-flight.” When possible, Emirates flights will be routed around areas of forecasted turbulence and avoid various weather phenomena to try to ensure smooth flying. But, Mr Hilderman says, no matter what, “aircraft will always fly in turbulence”. “The larger the aircraft, the less effect from turbulence – just like small versus large boats upon ocean waves,” says Mr Hilderman. “Turbulence literally moves an aircraft within the air away from its intended stable path and also affects flight control surfaces, such as the wings, aileron, lift and rudder.” Mr Schreiber says the most significant ways turbulence affects a flight are when it comes to passenger comfort and safety, crew workload, flight delays and reroutes, and aircraft stability. “It is important to note that turbulence in general is not a safety threat to modern aircraft,” he says. Mr Hilderman echoes this. “Aircraft are designed to be safer than any expected turbulence, with a wide margin for worst-case turbulence.” While the safety of modern, commercial aircraft is not in question, there is a threat to passengers on-board. “Unbelted passengers could die in extreme turbulence,” Mr Hilderman says. Mr Schreiber says passengers must keep their seat belts fastened, not just during instability, but at all times, as not all turbulence can be predicted. “Passengers who are not wearing their seat belts and are not properly secured are potentially at risk of injury,” he says. The other way travellers may be affected is via flight path changes. “In severe cases, flights need to be delayed or rerouted to avoid forecasted areas of turbulence,” says Mr Schreiber. Both Mr Hilderman and Mr Schreiber warn that some turbulence is unpredictable and that passengers should wear a seat belt. “Never leave your seat if you feel turbulence and return to your seat if it begins,” says Mr Hilderman. “Store loose belongings and sharp objects. In extreme turbulence, push your head back against the headrest firmly to avoid neck whiplash.” He also advises parents to hold infants firmly and place them in a belted carrier or, if possible, buy them a seat instead of holding them on their lap. You also might want to avoid hot beverages, Mr Schreiber adds, as they can splash or spill, resulting in potential burns. Most importantly, he says, stay calm. “Remember, turbulence might disturb your in-flight experience, but it is not harmful to modern aircraft.” No, says Mr Schreiber. Rather, it’s something passengers should be prepared for and informed about, he adds. “Almost every flight encounters turbulence at one stage during a flight”, Mr Hilderman says: “Even trained pilots and passengers with three million flight miles and 20,000 hours in the air occasionally have white knuckles and use the sick bag.” But aircraft are continually improving their designs, he adds. “So today’s aircraft in greater turbulence are still safer than prior aircraft in less turbulence.”

What is turbulence and why is it getting worse?

A recent report found bumpier flights are on the rise