Even the gentlest of turbulence can make a flight unpleasant. The chances are that it is only the gentlest kind you have experienced too, as bad as it may have felt at the time. ‘Severe’ turbulence, as pilots rate it – when things start to get thrown around the cabin – is rare, and extreme turbulence – when there’s chance of injury – almost never happens.
It does happen, of course, and you may even imagine you’ve experienced it. But by one estimate some 15 people are injured by turbulence each year in flights over the US, but that’s relative to the 2.5m people flying there every day. So, you likely have not.
Most injuries are the result not of damage to the aircraft – indeed, it should be reassuring to know that airliners are built to a standard that can withstand turbulence beyond anything that physics might throw at them. ‘We deliberately send aircraft into the eyes of storms to collect data. That tells you all you need to know about aircraft strength,’ says Jeremy Dempsey, flight director of California Aeronautical University.
Rather, the injuries come as a result of something much more mundane: not fastening seat-belts – which is why they’re most likely to happen to flight attendants, who are the last to sit down.
Bumpier Skies Ahead
That’s the good news. The bad news is that turbulence is getting worse. A study by the University of Reading reckons that turbulence strong enough to pose an injury risk could double or triple in frequency. That is, if you’re not wearing your seat-belt. The cause? Climate change’s impact on the troposphere – the lowest layer of Earth’s atmosphere.
It gets technical now, but the study says that wind shear – that’s the difference in wind speed or direction over a short distance – in the jet streams – those channels of faster moving air near the poles that airliners often use as their highways – has increased by 15 per cent at airliner cruising altitudes since satellites began gathering the data in 1979. It is projected to increase by up to 29 per cent by the end of the century.
‘Turbulence is, in effect, just chaotic air, in contrast to smooth-flowing ‘laminar flow’ air you ideally want,’ explains Isabel Smith, a meteorologist on the turbulence study team at the University of Reading. ‘Greenhouse gases are warming the troposphere at a faster rate and, in turn, cooling the stratosphere – and the steeper the temperature gradient the more chaos you get.’
Now some more good news. Most kinds of turbulence can be avoided. Most is caused by strong winds pushed up off of mountain ranges – this so-called ‘mountain wave’ is often the most dangerous kind of turbulence; or by air pressure changes caused by cold or warm weather fronts; or by convective thunderstorms. In-flight radar, satellite monitoring and a network of live reporting by pilots make these kinds largely ‘visible’ to aircraft, allowing them to fly around or over it.
And now some more bad news. Another kind, clear air turbulence, is on the increase too, by as much as 55 per cent over the Atlantic over the last 40 years. And because it doesn’t contain water droplets, like the other varieties, it’s not detectable. But new tech is coming on to make even that a thing of the past: LIDAR – that’s Light Detection and Ranging – systems are now being trialed, using an ultraviolet laser to analyse dust particles – rather than water droplets – in an aircraft’s path and so spot clear air turbulence coming.
Other systems involve fitting aircraft with sensors that feed data about the surrounding air back to a hub in real time for analysis, so each airliner plays a part in building an objective, updated picture of the global turbulence map.
Since turbulence is an incredibly complex system – effectively making it impossible to predict with great accuracy – faster computing power and AI will nonetheless also help in years to come. And it might be reassuring to know that airlines have every incentive to make such systems work, not least because turbulence costs them hundreds of millions in extra fuel and maintenance every year.
So are your flights going to get bumpier? A little maybe. Increased turbulence is more likely affect your travel in the form of making flights not so much bumpier, as longer – more turbulence means more turbulence to go around – or in delaying your flight’s take-off.
Conquering Turbulence Terror
Nothing, unfortunately, can stop turbulence from happening in the first place – turbulence, in fact, is crucial to the possibility of life on this planet. But what will help more nervous flyers, Dempsey suggests, is better education about what turbulence is (he’d like some reference made to it in the safety briefing, for example) and how it affects aircraft.
He has, he says, lost count of the number of times he has had to explain to people that airliner wings are designed to flex; or that the stomach-churning feeling is caused by a moment of weightlessness as the aircraft drops, at most, tens of feet, not the hundreds of feet imagined.
What does he recommend? Sitting at the back of the aircraft to start with, since turbulence has less effect there; and, his favourite trick, putting a glass of water on the table in front of you, thus providing a visual guide to how much the aircraft is actually moving. That, as it turns out, is hardly at all.
‘Turbulence can be terrifying for some passengers because it invites the fear of the unknown,’ he concedes. ‘It’s precisely because most flights are smooth that turbulence catches you off guard. You take your cue from the reaction of the passengers around you rather than what is actually going on. And remember that turbulence rarely lasts more than a few minutes as the pilot flies out of it.’
His number one tip though? ‘Just keep your seat-belt on. It’s as simple as that,’ he says. ‘I’ve been flying all my life. I know aircraft. I know turbulence. And I always keep my seat-belt on when seated. That may not make the turbulence any easier. But it does at least mean you will be just fine.’