What is Air Turbulence and is it Dangerous?

In 2013, 24 people (11 passengers and 13 crew members) were injured in turbulence-related incidents in the United States. Not a big number as such, considering that over 600 million people fly in the US every year.

On March 5, 1966, a BOAC (British Overseas Airways Corporation) Boeing 707 disintegrated and crashed into Mount Fuji in Japan shortly after the take-off, killing all 124 people (113 passengers and 11 crew members) on board.

In their final report, the investigators concluded that the probable cause of this disaster was severe turbulence over Gotemba City, which imposed a gust load considerably in excess of the design limit.

◆ Air Turbulence Explained

In the context of aviation, turbulence refers to violent movement of air, resulting from the confluence of two masses of air moving at different speeds.

According to the Federal Aviation Administration (FAA), it can be caused as a result of atmospheric pressure, jet streams, air around mountains, cold or warm weather fronts, or thunderstorms.

It is most likely to occur when you are flying through a mountainous region. It's also worth noting that the chances of encountering turbulence are more when you are crossing the ITCZ (Intertropical Convergence Zone), which marks the confluence of the northeast and southeast trade winds.

Air turbulence is usually accompanied by visual cues, such as clouds coming out of nowhere in an otherwise clear blue sky. At times though, it comes unexpected without any such warning signs. There are no visual cues for the pilot. This is called clear air turbulence (CAT).

In the absence of visual cues, the pilot may not be able to entirely avoid it, and thus, has to wait for it to pass. That explains why clear air turbulence is the most common form of air turbulence you are likely to encounter.

Wake Turbulence: Additionally, there is the case of wake turbulence, which forms behind an aircraft as it passes through the air. It can be attributed to wingtip vortices (circular patterns of rotating air left behind either wing as they generate the lift) or jetwash (extreme turbulence caused as a result of rapid movement of gases expelled from the engine).

An aircraft is most likely to encounter wake turbulence when it is about to take off or land after another aircraft. Air traffic controllers keep a considerable space between two airplanes―especially when the first one is bigger―to ensure that the second airplane doesn't get caught up in wake turbulence.

◆ Is Air Turbulence Dangerous?

If you are worried that turbulence will bring down your airplane or cause it to explode, then you can relax. With all the safety precautions that airlines take, not just when the aircraft is in flight but also when it is in production, you need not worry about turbulent weather bringing it down.

There have been such cases in the past―the BOAC Flight 911 incident being an apt example of the same―but now airlines are better equipped to handle such weather anomalies.

That, however, doesn't mean there are no safety issues. While it may not be life-threatening, turbulence does pose a threat; albeit, at a lesser level. There is no specific technology in the airplane to warn the pilot about approaching turbulence.

If the pilot is able to warn you to fasten your seat belts in the event of turbulence, it is because he relies on real-time reports from other airplanes that have flown by that path earlier, and weather reports from the Air Traffic Control (ATC) which are based on forecast systems on the ground.

As it is, all pilots expect some turbulence in their journey, especially those who fly across the equator. They rely on visual cues to identify turbulent areas in the sky, and if necessary, even change the route of the airplane.

All pilots are trained to handle turbulence and turbulence-related issues. For them, it is mere inconvenience that comes with the slogan: this too shall pass. In the event of turbulence, they can change the speed and altitude of the aircraft to make it through in a smooth manner.

They also have to option of resorting to the Turbulence Penetration Speed, i.e., the manufacturer-specified ideal speed at which an aircraft can handle heavy turbulence.

Furthermore, airplanes nowadays are designed to withstand an enormous amount of stress that they can be subjected to during heavy turbulence. Even gigantic Boeing airplanes nowadays have wings that flex.

Then there is the concept of positive stability, which states that when an object is displaced from a particular position in space, it tends to return to its original position.

Most safety concerns about turbulence crop from hearsay, rather than personal experience. Even passenger accounts shown in news are mostly exaggerations; at times, even going to the extent of comparing turbulence with rough seas. More anxious the passenger, more exaggerated his account is likely to be.

Then there are limelight-hungry people who literally brag about how their flight dropped 1,000 ft. in two seconds. Despite what passenger accounts may have you believe, an airplane is seldom displaced more than 20 ft. in altitude during turbulence.

◆ What About In-flight Injuries?

So there are absolutely no safety concerns about flying in turbulent weather? Like we said earlier, it may not be life-threatening, but it does pose a threat of in-flight injuries. Though rare, the chances of people getting injured during turbulence cannot be ruled out.

If someone has not fastened his/her seat belt, the chances are that he might be thrown out of his/her seat. Then there is the threat of baggage falling from overhead bins. And turbulence being an 'act of god', airlines can't be held liable for the injuries. So, it is wise to take precautionary measures and follow all the instruction given by the flight crew.

Of the 24 people injured in turbulence-related incidents in 2013, 13 were crew members. In 2012, 21 of the 32 injured were crew members. As you see, the flight crew is at the most risk of ending up with an injury in the event of air turbulence.

That shouldn't really come as a surprise, considering that they are mostly out there comforting anxious passengers during a bumpy ride. Other than crew members, children on laps are also at a risk of ending up with an injury, as a result of being flung off your lap during a bumpy ride. And lastly, there are passengers who don't fasten their seat belts.

While pilots do their duty and put on the seat belt sign when the airplane encounters turbulence, most people tend to ignore it. An apt analogy here will be the story of the boy who cried wolf. If you are really worried about your safety, you should fasten your seat belt throughout the journey.

It's not uncomfortable and a few minutes into the journey, you won't even realize that you have the seat belt on. That's unless you really want to see the 'wolf' to take him seriously.

Post Script: A study published in the Nature Climate Change (April 2013 issue) suggests that the frequency of turbulence could increase by anywhere between 40 percent and 170 percent by 2050; courtesy, as a result of global warming-induced climate change. Expect a bumpy ride ahead!