Experts weigh in on possible causes of turbulence on Air Canada flight

theglobeandmail.com ^ | Thursday, Dec. 31, 2015 9:42PM EST | ERIC ANDREW-GEE

[BenLurkin]

The Transportation Safety Board (TSB) continued its investigation of an incident in which passengers were thrown from their seats and objects hit the cabin ceiling during a harrowing few minutes that forced the Toronto-bound flight from Shanghai to stop in Calgary for medical help.

...

Rod Hayward, an aviation expert at the University of the Fraser Valley, said sudden turbulence in clear skies can sometimes be caused when a plane flies through a jet stream, a kind of narrow, fast-moving current of air. That sudden increase in air velocity, sometimes reaching 100 knots, can cause aircraft to shake violently, he said.

Because jet streams are invisible, they can take pilots by surprise, Mr. Hayward noted. Forecasts can often predict the location of the air patterns, but they move and change direction quickly.

...

Pointing to passenger reports of rapid up and down movement in the plane, Wayne Hocking, a physics professor specializing in atmospheric turbulence at the University of Western Ontario, said that breaking “gravity waves” were a more likely culprit. Those are undulating currents of air that can cause severe up-and-down turbulence for aircraft. They can be caused by a range of factors, including heat from the ground, or hot and cold air fronts colliding in the atmosphere.

But in this case, Prof. Hocking said, it is probable that any gravity wave would have been caused by air flowing over the mountains of Alaska below. When air goes over a mountain it continues moving in the pattern of the mountain peak rather than flattening out, and before moving as a wave into the upper atmosphere, Prof. Hocking explained.

[doorgunner69]

a physics professor specializing in atmospheric turbulence at the University of Western Ontario, said that breaking "gravity waves" were a more likely culprit.

Cough, cough. And this guy has tenure?

Let me guess, he is on board with man made global warming as well?

[Daniel Ramsey]

Massive warm air front coming up from Japan caused 100mph winds in and around Anchorage, from what i heard the incident occurred over Alaska. Temperatures are very much warmer than normal, warmer than Los Angelos.

[onyx]

That EVIL climate change!

[aviator]

Keep your seat belt fastened and you won’t hit the ceiling.

[Rockpile]

It’s 28F in Nome right now. LA might be warmer. ;<}

[Mark17]

That EVIL climate change!

Don't you just hate global warming? If the Aswan dam leaks in Egypt, some nut case will claim it was caused by global warming.

[BenLurkin]

[TexasGator]

You have a problem?

[TigersEye]

So, the cause was narrowed down to air!?

[This_far]

Gravity has always been my first consideration in any plane disturbance, especially crashes.

I’ve only crashed once, fortunately, I was still on the ground.

[cynwoody]

when a plane flies through a jet stream, a kind of narrow, fast-moving current of air. That sudden increase in air velocity, sometimes reaching 100 knots,

The other day, I flew from Denver to Boston. The flight was pretty smooth, but, when I took out my GPS, it showed a ground speed of 659 mph at 37,571 feet over Ontario. A 727's typical cruise speed is 540 mph.

[dr_lew]

"In the Earth's atmosphere, gravity waves are a mechanism for the transfer of momentum from the troposphere to the stratosphere. Gravity waves are generated in the troposphere by frontal systems or by airflow over mountains. At first, waves propagate through the atmosphere without appreciable change in mean velocity. But as the waves reach more rarefied (thin) air at higher altitudes, their amplitude increases, and nonlinear effects cause the waves to break, transferring their momentum to the mean flow."

- Gravity Wave at Wikipedia.

So ... C'mon man !

And I have to add ... I knew this! ( Well, mostly. )

[this_ol_patriot]

Better check this out, yeah I know, I know I learned something too.

https://en.wikipedia.org/wiki/Gravity_wave

[onedoug]

I’ve been in turbulence severe enough for me to swear that would be my last flight...only to take off again within 6 months.

[Mogger]

When I was a tech in a precision measurement Equipment Lab in the Air Force, we had to measure gravity daily as the changes affected some of our instrumentation and calibrations.

There's a little difference between being a doorgunner, and placing a bomb precisely, within millimeters on the other side of the world from where your plane took off.

And then with any luck, getting home to load up and make another run.

There's a huge amount that of expertise that comes into play, from the guy who airs up the tires to the guy who calibrates the equipment.

Of course, being a doorgunner requires less scientific knowledge, but huge cajonies and a different expertise.

Takes a team, from the infantry guy slogging in the mud to the techie nerds to win anything.

[Flick Lives]

Gravity waves?! And this prof found them? Call the Nobel committee.

[Organic Panic]

Being a recovering aircraft engineer I only worry about spilling my little liquor bottle on flights. Always replace the cap after each sip. And keep that belt fastened.

Truth be told... I am always worried when I am in the head. I have been in some rough stuff and....well... there’s a reason you don’t want to be in the lavatory.

[Bulwyf]

He’s an idiot and not using any real terminology. I think he made that up on the spot.

[Bulwyf]

Hot air rising is called thermals, wind hitting a mountain and rising is called a mountain wave. That’s the way I learned it when training to fly. I’ve never once heard of gravity waves.