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Interview transcript

[STARTS]

Tim Benjamin: When you’re flying, does the first hint of turbulence turn you into a quivering wreck?

If so, you’ve got to check out today’s episode.

Because joining me are two of the world’s leading turbulence experts to reveal what turbulence is.

And what it means for YOU when you’re at 39,000 feet.

Hi there – I’m Tim Benjamin with the Fear of Flying School podcast.

And today, my guests are Dr Bruce Carmichael and Dr Bob Sharman from the US Government’s National Center for Atmospheric Research – otherwise known as NCAR.

To get the ball rolling, I asked Bruce to explain what NCAR does.

Dr Bruce Carmichael: National Center for Atmospheric Research – shorthand NCAR – is a Federal laboratory here in the United States.

It is an agent of the National Science Foundation – and this organization studies the atmosphere, does research and development of things all the way from space weather and the Sun down to weather forecasting, weather sensing, climate change.

And also provides facilities for universities to do research.

We have super-computers and aircraft and radars that universities use.

Tim Benjamin: And where do turbulence and aviation fit in with your remit?

Dr Bruce Carmichael: Well, the particular laboratory that Bob and I are in is called the Research Applications Lab. And our Lab focuses on real-world atmospheric problems – and trying to come up with solutions that help mitigate those problems.

So our group – the Aviation Applications Program – is really looking at atmospheric problems that affect aviation – both from a safety standpoint as well as efficiency and delay and air-space capacity and all those things that airlines and air traffic control authorities are interested in.

Tim Benjamin: So, talking about you specifically, Bruce, what do you do?

Dr Bruce Carmichael: So, I’m the Director of the Aviation Applications Program here, and we have a number of subject matter areas that we work on – turbulence being one of those.

We also do research on thunderstorms.

We do research on icing – aircraft icing, ceiling and visibility.

We do work on both domestic and oceanic kinds of problems.

And we do work on the engineering side of how you get this information out to the people who need it.

Tim Benjamin: And joining me is your colleague, Bob Sharman. Bob: can you tell me what do you do?

Dr Bob Sharman: Yes – OK – so I’ve been at this Lab for about 15 or 16 years. And almost that entire time, I’ve been looking at mainly procedures for better predicting turbulence – especially turbulence at commercial aircraft altitudes.

And – um – you know, we’ve developed several forecasting algorithms that are available publically now – and are used by some of the airlines.

And the idea is that with a better forecast of turbulence, they can avoid it.

We also work on better methods for detecting turbulence – either remotely or in-situ.

Tim Benjamin: What is air turbulence?

Dr Bob Sharman: Turbulence is basically bumpiness in-flight.

It’s caused by irregular air motions.

Tim Benjamin: So, to be clear, is it fair to say that air turbulence is simply caused by different bodies of air intermingling with each other – a bit like water in a stream kind of bouncing around rocks and pebbles for example?

Dr Bob Sharman: That’s actually a good analogy. That’s right.

If you look at a stream and you see that stream is smooth but then it flows over a rock. And the water motion becomes chaotic, then that’s turbulent.

And, actually, the same thing happens, to a degree, when air flows over mountains: you can’t see that little perturbation in the stream as you can in the water stream, but the same kind of thing is happening – it’s flowing over the mountains – and it starts to become ‘chaotic’ as it does so.

Tim Benjamin: It’s interesting – when people talk about turbulence, particularly nervous passengers, they often talk about their plane hitting so-called ‘air pockets’.

Is there such a thing as an ‘air pocket’?

Dr Bob Sharman: Well, I personally don’t like the term ‘air pocket’ because I’m not quite sure what it means.

It sounds like there’s this invisible vacuum out there that an airplane falls into – and who knows what’s going to happen to it.

Um – what’s REALLY happening is that once this turbulence is generated, part of the component of it is ‘up-draughts’ and ‘down-draughts’: vertical excursions of the air.

Tim Benjamin: In other words, some air moving up and some air moving down?

Dr Bob Sharman: That’s correct.

And so when an aircraft hits that, and the magnitude of those up-draughts and down-draughts are large enough, it may force the aircraft UP – or it may force the aircraft DOWN.

When it goes DOWN, I think that’s what a lot of people are referring to as ‘air pockets’.

But it’s simply the fact that the airplane hit some downward motion that it wasn’t expecting.

Tim Benjamin: So, just to be clear, when the plane is going down, it’s STILL supported by air? It’s NOT in free-fall?

Dr Bob Sharman: Oh – absolutely. There’s still lift on the wing, which I think you’ve talked about in other interviews.

And – uh – that lift of the wing is always MUCH more than the downward motion of the air that’s pushing it down.

So it’s NOT going to fall out of the sky.

Tim Benjamin: Are there different intensities of turbulence?

Dr Bob Sharman: There definitely are.

And – um – and usually they’re classified by pilots in certain ways, depending on how it affects the aircraft.

There’s actually several degrees that pilots describe turbulence intensity as fitting in to.

One is ‘light’ turbulence where there is just small, momentary, fluctuations. The passengers may not feel much of anything except a slight strain against the seat belt.

The next category up from that – where these up-drafts and down-drafts are larger – and the aircraft’s response is a little greater – is called ‘moderate’ turbulence.

Passengers feel strains against the seatbelts. Objects can be dislodged, slightly.
But usually, as the intensity of the turbulence goes up, its lifetime DECREASES.

So that the STRONGER the turbulence event is, the SHORTER it is.

Tim Benjamin: Now when you say ‘shorter’, what do you mean?

Dr Bob Sharman: In terms of time.

Tim Benjamin: In other words, if I’m on a plane that’s going through what feels like quite intense turbulence, that period we spend in the turbulence is likely to be shorter than when we’re flying through light turbulence?

Dr Bob Sharman: That’s correct.

Yeah – the next category up that – I didn’t finish – was ‘severe’ turbulence: extreme jarring.

If you think of a coffee cup, the coffee cup’s probably spilling a lot of liquid at this point.

And there’s even an ‘extreme’ category where the aircraft is starting to be tossed around very violently. This is a VERY rare event, however.

Tim Benjamin: If you speak to people who hate turbulence, they’ll probably tell you that they’ve had quite a lot of experience of the two most violent forms of turbulence that you’ve just described.

Is that likely?

I mean, are these common, every day events?

Dr Bob Sharman: That’s what they remember. But I don’t think that they’re remembering the 98% of the flight that was smooth.

Turbulence is actually a rare event.

We have these special sensors on commercial aircraft that measure the turbulence all the time and report it back down to the ground so we can see it.

And 98% of the time, these flights are smooth: there’s no turbulence at all.

So, it is a VERY rare event.

And that other 2% is mostly in this ‘moderate’ category which is really not affecting the aircraft very much – but the people are feeling uncomfortable.

Tim Benjamin: To what extent does turbulence impact on the operation of an aircraft?

Dr Bob Sharman: If it’s strong enough, they will divert other aircraft from that area. It usually has to be VERY strong – in the ‘severe’ category – before they will do that.

Otherwise, pilots speak to one another in-flight and they tell them that this area that they just passed is, say, ‘moderate’ turbulence, and if other aircraft approaching that area can avoid it, by climbing or going around, they will.

Usually.

But that’s sort of an airline policy.

Because you see, to avoid turbulence, you have to change route.

That requires some amount of fuel.

Extra fuel.

And, sometimes, the airlines are not willing to make that trade-off.

Tim Benjamin: Like most frequent fliers, I’ve been on planes that have gone through turbulence. And I’ve often wondered – you know – if the pilot knew about this in advance, why are we still flying through it.

Dr Bruce Carmichael: Well, you know, often the pilot doesn’t know in advance. There might not be an aircraft on the same route giving reports of turbulence.

Or, oftentimes, if it’s ‘light’ turbulence, the airline and the pilot will make a decision just to continue on through.

But, operationally, one of the biggest issues with turbulence, really, is the fact that it impacts the service in the cabin.

You have flight attendants who are trying to provide drinks and food and be up and down the aisles doing things.

And it doesn’t take very much turbulence before providing that service has some difficulty.

You know, you’re coffee may be jostling a little bit on your tray.

And the airlines really don’t like that. They don’t like to have their passengers worried about whether the coffee is going to get in their lap.

Tim Benjamin: If you’re worried about turbulence, usually a bit of coffee in your lap is the LAST thing you’re worried about.

The REAL concern is that the plane’s going to fall apart.

Dr Bruce Carmichael: Well, it’s the coffee in the lap that sort of triggers the pilot to be trying to find a spot to get rid of the turbulence.

It’s not that they’re concerned about the safety of the aircraft or the passengers.

It’s they’re concerned about having the passengers be uncomfortable, the flight attendants not being able to perform their service very easily.

And so then they’ll start looking for a better altitude, a smoother altitude.

And they’ll go usually up or down to try to find a smoother altitude.

Tim Benjamin: So, just to be clear, when a plane encounters turbulence, the thing that’s on the mind of the pilots is really ‘how can we avoid coffee winding up in people’s laps?’ rather than ‘how do we stop the plane falling apart?’?

Dr Bruce Carmichael: Yeah – that’s absolutely right.

Dr Bob Sharman: Since I’ve been here – 15 or 16 years – and even going, probably back 20 years, I cannot recall a SINGLE aircraft going down – commercial aircraft going down – because of turbulence.

Some aircraft have been damaged.

But I’ve NEVER heard of one actually falling out of the sky.

Tim Benjamin: Well, on the subject of damage, what sort of damage are you talking about?

Dr Bob Sharman: Some damage is to the outside.

Some damage is to the inside.

Outside damage might be, part of a wing or something is torn loose.

It still doesn’t mean it can’t fly.

And it DOES fly.

There was an incident that I’m aware of where an aircraft took-off from Seoul, Korea – had a little bit of damage to the wing going out of the airport.

But they didn’t know that.

They flew all the way to San Francisco without incident – and then later saw the damage to the wing after it had landed.

So, that’s just to say that even with some external damage, the aircraft’s not going to fall out of the sky.

Tim Benjamin: When a plane is flown through turbulence, is there a need to do any kind of inspection on it after its landed?

Dr Bob Sharman: The rule is, if the pilot perceives that turbulence encountered to be in the ‘severe’ category, the rule is that, yes, they should take that aircraft out of service and have the mechanics do an inspection on it to make sure there’s no damage BEFORE they use that aircraft again.

Tim Benjamin: We’ve talked about what turbulence is. And we’ve talked about how it impacts on the performance of an aircraft.

Let’s just talk a bit about how pilots go about avoiding turbulence in the first place.

Can you walk me through that?

Dr Bob Sharman: That’s one of the reasons we are working on forecasting algorithms, so that the first thing the pilot could do is when he’s planning his route, is to avoid areas of forecasted turbulence.

Now – again – this has to be weighted against how far that’s going to take him away from his ORIGINAL planned route.

If he’s in-flight, then he has two options if he wants to avoid the turbulence.

He can either climb or descend, which is usually the most cost-effective and – actually – the better way of doing it because in the upper atmosphere, where these commercial aircraft fly, the depth of the turbulence zone is VERY narrow.

So, you don’t have to climb very far – or descend very far – to get out of the turbulence.

And I think you probably all noticed that in-flight.

So – look for what they call ‘smoother altitudes’.

As opposed to flying around a big patch.

Now, sometimes it’s, for example, a big thunderstorm.

The only way you could avoid that is to go around it.

But usually – if the air is clear – these turbulent patches are very thin in the vertical and so it’s just simpler – and more efficient – to climb or descend.

Dr Bruce Carmichael: If you ever have the opportunity to listen to the air traffic control pilot communications channel, which some of the airlines make available to the passengers, one of the things you’ll note is while the cruise flight is going on, almost the whole conversation between the pilot and the controller either involves passing the aircraft onto the next controller by changing frequency.

Or questioning ‘How’s the ride?’.

Or the pilot saying ‘I’m experiencing some light to moderate turbulence. Is there a better altitude?’.

And, so, in a sense – in today’s system – the controller and the pilot are very much talking to each other.

And, in fact, all the other pilots in that same air traffic control sector are talking on the same frequency.

So, it’s like a party line and they’re all listening to each other.

Tim Benjamin: Quite often I’ve stepped onto a plane and before we’ve taken off, the Captain’s come on to the public announcement system and said ‘Look – as soon as we get airborne, it’s going to be a bit bumpy for a few minutes’.

In that scenario, wouldn’t it be better – wouldn’t it be more comfortable – would it not be safer – just to say ‘Look, we’ll stay here on the ground and wait until the storm passes’?

Dr Bob Sharman: Yeah, but these airlines are operating at almost 100% capacity as it is.

So, if you start delaying traffic because of turbulence, pretty soon the backlog will be so large that you’ll never be able to recover from it.

Dr Bruce Carmichael: And the truth of the matter is that in terms of safety, if people are belted into their seats, and in more difficult cases, if the flight attendants are belted into their seats, everybody is secured.

And if the food and drink carts are secured, and not sitting in the middle of the aisle, then there’s really not much of a safety issue involved.

And you’ll see oftentimes the pilots get on the PA system and say to the flight attendants, ‘Please be seated’.

And the flight attendants will pretty quickly scramble and get into their jump-seats and belt in.

Tim Benjamin: Now that’s going to be the sign for a lot of nervous fliers to panic.

Dr Bruce Carmichael: Well, it’s just saying that it’s not safe to be walking up and down the aisle. We may hit a bump that will throw you down.

Or could injure you by bumping your head on something.

Or having something hit you.

So, it really is….passengers who are belted in are very rarely injured.

Dr Bob Sharman: Yeah – in fact, 97% of injuries that occur on an aircraft – on a commercial aircraft – are people that do NOT have their seatbelt on.

Tim Benjamin: Obviously, whenever you get on a commercial flight, you’re told over and over again to keep your belt on if you’re not walking around the cabin – even if there is NO turbulence.

But it’s quite rare for an announcement to explain WHY that’s so important.

Are you saying that when you hit turbulence, there’s a chance that people and things will start flying around the cabin?

Dr Bob Sharman: Right – or if you’re walking down the aisle, maybe that – even if it’s a little bump – it catches you off-guard and maybe you fall down or something and hurt yourself.

When I fly, I ALWAYS keep my seatbelt on.

Dr Bruce Carmichael: But this is really the danger.

The danger is the injury to the people in the aircraft who aren’t secured.

And, of course, the vulnerable people are those flight attendants because their job is to be up and around and doing things in the cabin.

And I’m always a little uncomfortable when it starts getting fairly bumpy and I see the flight attendants up and down the aisle collecting empty cups and trash.

And I’m thinking ‘If that were me, I’d rather be seated thank-you very much – with my seatbelt on’.

Dr Bob Sharman: Right – and there’s a statistic that supports that – and that is of the injuries that are reported every year, 40% of those injuries are flight attendants.

Tim Benjamin: 40%!!! Which is extraordinary because they’re not 40% of people who’re travelling on planes.

Dr Bob Sharman: That’s correct – they’re only like a few percent – 4% or so.

Tim Benjamin: Speak to someone who hates turbulence and they’ll SWEAR that the last time they were in a plane that hit turbulence, the plane was dropping like a rock – or dropping hundreds of meters per second.

What’s ACTUALLY happening to a plane when it’s going through turbulent air?

Dr Bob Sharman: Typically, when we look at accident data – by ‘accident’ I mean that someone was injured on the aircraft after a turbulence encounter – if you look at the VERTICAL motion of the aircraft – even if it’s a BIG event – that motion is only like 50 feet or so.

It’s not very much at all.

Tim Benjamin: So, how does a 50 foot drop FEEL so big?

Dr Bob Sharman: I don’t know – I think it’s just partly psychology.

Dr Bruce Carmichael: Of course, if you were 50 feet up in the air – 5 stories up in the air – and suddenly dropped toward the ground, that WOULD feel like a big drop.

Dr Bob Sharman: Personally, I’ve only experienced that twice – and I’ve flown over a MILLION miles.

So – again – I just have to emphasis that’s a REALLY rare event.

So if somebody experienced that, they were VERY unlucky.

Tim Benjamin: So, if I get on a plane today, and I hit some turbulence – which happens a lot – the chances that I’m actually going to drop 50 feet in one pop are slight?

Dr Bob Sharman: Yeah – I would say that’s something in the order of a one-in-a-million chance.

Tim Benjamin: You’ve obviously both been in aircraft when they’ve hit turbulence. And, Bob, you’ve just mentioned that you’ve experienced severe turbulence twice.

As people who are experts in this field, what’s going through YOUR heads when you’re on a plane and it’s bouncing around?

Dr Bob Sharman: For me personally, I know that, as I said earlier, a severe event like that will last for a VERY short time interval – maybe just a few seconds.

So, I know I’ll be out of it in just a few seconds.

And that’s helpful to me, personally.

Also, I know that these airplanes are WAY over-built. As I said earlier, I don’t know of anyone who EVER went down because of turbulence.

It’s just not something I’m concerned about.

Dr Bruce Carmichael: My concern, usually, is that I look around and I see one or two passengers who still feel the need to be up and headed to the restroom.

And I’m thinking ‘This is NOT a good time to be going to the restroom’.

I can’t think of a worse place to be in moderate turbulence than standing in that little tiny restroom in the tail of the aircraft.

Tim Benjamin: The tail of the aircraft? Does it matter where you sit on a plane in terms of comfort when going through turbulence?

Dr Bob Sharman: It DOES. The tail of the aircraft DOES experience a lot more motion for the same level of atmospheric turbulence.

Tim Benjamin: So, where’s the best place to sit if you want relative stability?

Dr Bob Sharman: Over the center of gravity – which would be around the wings somewhere.

So, sitting over the wings if you can do that.

Tim Benjamin: And what about the front of the plane? How does that compare?

Dr Bruce Carmichael: The food is better [laughs].

Dr Bob Sharman: I’m hardly in the front, so I don’t know [laughs].

No – usually when I’ve been there, it seems like it’s smoother.

The tail is by FAR the worst.

Tim Benjamin: I just want to finish off on a point that you made before, Bob. And that is ‘how long turbulence lasts’.

You said that the more intense the turbulence, the shorter it lasts for.

If somebody is going through turbulence that is sufficiently strong to throw their coffee all over the place, typically, how long is THAT turbulence likely to go on for?

Dr Bob Sharman: Just a few seconds.

Tim Benjamin: So the whole thing is likely to be over in a few seconds?

Dr Bob Sharman: Yes. Now you may experience LOWER levels of turbulence AFTER that. But it won’t be anything like that.

Tim Benjamin: And why is it that the more intense turbulence only lasts a very short period?

Dr Bob Sharman: Because turbulence doesn’t like to stay turbulent.

It likes to mix up the air and smooth itself out.

It’s just kind of the way it works.

Tim Benjamin: A final question for you both: what is the future of turbulence apropos of the passenger experience?

Dr Bob Sharman: I think that right now, we’re looking at better detection techniques, better forecasting techniques.

And these are getting better all the time.

And I’m sure the turbulence experience will continue to decrease.

Dr Bruce Carmichael: We’re also looking at advanced design aircraft that will be coming into the market place that will have look-ahead sensors that can see a short distance in front of the aircraft.

And will be able to moderate the aircraft behaviour as it enters an area of turbulence.

So that the aircraft itself will help dampen some of the turbulence.

Tim Benjamin: And when are we going to see those technologies start to come on-stream?

Dr Bruce Carmichael: Actually, you already ARE seeing some of that technology with the new Boeing 787.

One of the things that’s happening right now as we speak is that Delta Airlines is actually flying trials where they’re using our turbulence detection algorithms to get turbulence from the aircraft to the ground.

And thus be integrated in with the forecast information that’s sent to the cockpit on iPads where the pilots can actually get a good 4-dimensional view of turbulence around them.

And help them make better decisions.

So, I think that’s the future of turbulence avoidance is with the pilots in the cockpit in real time to be able to see on something like an iPad – which they call an Electronic Flight Bag – to actually see in real time the turbulence environment that they’re flying through.

Tim Benjamin: This has been a really fascinating conversation. All that’s left, really, for me to do is to thank both of you: Dr Bruce Carmichael and Dr Bob Sharman for joining me on the Fear of Flying School podcast.

Gentlemen, thanks for coming.

And thanks for joining me.

Dr Bob Sharman: Our pleasure – thank you.

Dr Bruce Carmichael: Enjoyed it.

[ENDS]

Your thoughts on air turbulence…

As you know, people respond differently to turbulence. Even those who have a fear of flying aren’t always troubled by it (for some reason I never was). Tell me in the comments how YOU feel about it.

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