4 Jun 2024

Our turbulent skies

From The Detail, 5:00 am on 4 June 2024

Buckle your seat belts - those bumpy rides are becoming more frequent, thanks to climate change

Singapore Airline's new Airbus A350-900ULR which will embark on the world's longest non-stop plane journey.

Singapore Airline's new Airbus A350-900ULR which will embark on the world's longest non-stop plane journey. Photo: Supplied/Singapore Airlines

Driving at 500 kilometres an hour along a severely bumpy road - that's what it's like to steer a plane that's going through the worst turbulence - and that's exactly what pilots are trying to avoid.

"It does create a bit of nervousness amongst the minds of passengers," Massey University school of aviation chief executive officer Ashok Poduval tells The Detail.
"There are two turbulence incidents which have happened in quick succession - the fact of the matter is, it's really pretty much coincidental. 

"If you look at a FAA [Federal Aviation Administration] report, in 10 years from 2012 to 2022, only 34 passengers were seriously injured in 163 turbulence instances, so it's very low. It's over 25 years since a passenger has been killed in commercial aircraft turbulence - that was in 1997."

That was until May 22 this year, when a passenger died of a suspected heart attack and 30 people were injured after a Singapore Airlines Boeing 777-300ER hit turbulence. 

"We experience wind gusts every day and that's turbulence," NIWA meteorologist Richard Turner tells The Detail.
"Higher up, generally the flow is quite steady. If you've flown on an aircraft, the take off can often be quite bumpy, you get above and things tend to smooth out. There can be instances though, particularly if you're flying over mountain ranges or something, there can be large undulations in the airflow... sometimes turbulence can be generated around that or generated by thunderstorms where you get rapidly rising columns of air."

Turbulence is very common - but the severe and extreme events are not.

"What we see a lot of the time is either light or moderate," Poduval says.

"Mostly, pilots will be avoiding severe turbulence if they know it's out there, unless you have issues like clear air turbulence."

And that can be difficult to anticipate.

"Jet streams are really the cause of clear air turbulence," Poduval says. "Basically, these are tunnels at higher altitudes. They are tubular currents of air that travel at a high speed. 

"Generally, the core of the jet stream has high velocities as high as 200 miles per hour. This speed drops off towards the edge of the jet stream and that's where the turbulence can be severe or even extreme. These are predictable, they are monitored so pilots have the information in advance. But having said that, they do shift, they are not completely static and the predictions can't be that accurate. So sometimes flying along, at maybe 35,000 feet, clear air, and suddenly you hit a bit of turbulence." 

Evidence also shows turbulence is becoming more common with the impacts of climate change.

"There have been some recent studies showing increases in instances of clear-air turbulence - about a 15 per cent increase over the last 40 years," Turner says.

"The reason would be the jet stream ... the faster jet streams are going to be faster. There's going to be an increase in the very high-altitude winds at times. That is related to the equator - we expect that it'll get warmer and moister."

Poduval says there are several aircraft improvements that will help counter turbulence.
"For example, the wing-tip of a 787 and even some of the other larger aircraft - the wing tip actually moves up and down by almost maybe several feet when the aircraft is in flight. That flexibility allows you to ride - it's like the springs or the suspension on a car going around a bumpy road."

He also talks about NASA carrying out research to see if special microphones can pick up clear air turbulence through ultra low-frequency soundwaves.

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