What is turbulence and how can it be avoided?
Everyone has experienced a bout of turbulence when traveling on a commercial flight or private jet. It could have lasted a few moments or an hour – usually when you’re about to enjoy a beverage or need to use the restroom. Turbulence is a common occurrence on most flights – but what is turbulence? How is it caused and is it dangerous? We answer the most common questions and dismiss myths about turbulence.
Let’s look at the reasons why it happens.
Types of turbulence
You have probably heard that bad weather causes turbulence, which is not wrong. However there a range of factors that cause turbulence.
Mechanical Turbulence: This is caused by irregular air flow over the surface of the Earth, usually caused by hills, mountains and buildings. Friction between the air and the ground causes eddies and irregular wind flow patterns, so during take-off and landing the turbulence can be more pronounced.
Mountain Wave Turbulence: As air travels over mountain ranges, turbulent eddies are created downwind and cause a wave-like pattern. These breaking waves and rotors can create severe turbulence and can be found for hundreds of miles downwind from a mountain.
Frontal Turbulence: A weather front is caused when two different air masses of different densities and temperatures begin to transition. Cold fronts are associated with thunderstorms and warm fronts with fog and precipitation. Frontal turbulence is caused by friction between the two air masses and most commonly with fast moving cold fronts.
Clear Air Turbulence: This is most common in the cruise stage of flight, above 15,000 feet. It is caused by wind shears in the jet stream. What is wind shear? Wind shear is caused by sudden changes in wind speed and direction, both vertically and horizontally. Wind shear is often related to jet streams. A jet stream is a ‘river’ of fast-moving air in the atmosphere – sometimes traveling up to 250mph. Usually flowing from West to East, aircrafts use them to travel faster and cut fuel costs. When the jet stream encounters slower moving air or wind shear, turbulence is caused. Clear air turbulence is more frequent during winter months and is impossible to detect with instruments or the eye.
Thermal Turbulence can be categorized as a form of Clear Air Turbulence: The sun heats the Earth’s surface unevenly – barren earth, rocky and sandy areas and desert are heated more rapidly than grass fields and much faster than water. As warm air rises and cooler air descends, the rising and falling currents cause bumpy conditions as the aircraft flies in and out of them. If a pilot expects thermal activity on a flight, they may prefer to fly early in the morning or in the evening when the thermal activity is not as pronounced.
Wake Turbulence: When an aircraft travels through the air it generates a wake which in turn can cause wake vortex turbulence. Airflow traveling over the wings generates swirling air masses downstream of the wing tips. The wake now consists of two counter-rotating cylindrical vortices. They can exist for a few minutes depending on altitude and wind speeds and is a risk to other aircraft in the vicinity – especially business jets and light aircraft.
Thunderstorms: Cumulonimbus clouds – commonly associated with thunderstorms – cause vertical currents which can displace an aircraft up or down vertically as much as 2,000 to 6,000 feet. In some cases, they can be severe enough to stall an aircraft. To avoid thunderstorms aircraft pilots usually have two options. The standard procedure is lateral deviation of 20 nautical miles. The second option is to fly above the clouds, however this is usually a last resort.
Now we know more about the causes of turbulence there are also different turbulence categories. You have probably experienced light turbulence, but there are other categories:
Light turbulence briefly causes slight changes in altitude. Passengers may feel a slight strain against their seat belts. The aircraft drops/rises around 1 meter.
Moderate turbulence is more intense than light turbulence. There is no loss of control of the airplane. Passengers will feel a strain on their seatbelts, objects will be dislodged, and drinks may spill. The aircraft drops/rises around 3-6 meters.
Severe turbulence causes large and abrupt changes in altitude. The aircraft may temporarily be out of control. Passengers will be moved aggressively in their seats. The aircraft drops/rises around 30 meters.
Extreme turbulence the airplane is tossed around violently and cannot be controlled. It may cause structural damage.
Is turbulence dangerous?
Turbulence itself is not dangerous and aircraft are built and tested thoroughly to withstand even the most extreme turbulence. However, it is when items or people in the cabin are not secured that can cause injuries. When the seatbelt button is illuminated by the pilot, this is to ensure passengers are not thrown around the cabin causing injury. Most injuries reported due to turbulence are cabin crew, who often are performing their duties in the cabin when spells of turbulence occur.
Can you avoid turbulence?
The best way to avoid turbulence is flight planning. Using the latest weather tracking and meteorological reports, dispatch teams will use all the data available to them to develop the best flight plan avoiding adverse weather. During flight, reports are shared with other aircraft and ATC (Air Traffic Control) to warn them of any turbulence or changes in weather. Speak to the Jetex Flight Planning team for trip planning, dispatch and flight following.
Can pilots spot turbulence?
Experienced pilots will be able to spot potential turbulence caused by weather fronts or routes associated with turbulence, however it is difficult to say for definite when turbulence will occur with the naked eye.
As it’s difficult to predict and avoid turbulence, it’s difficult to say what are the most turbulent flight routes. However, in the case of Mountain Wave Turbulence, mountain ranges like the Rockies, Andes or Himalayas are commonly associated with turbulence and flight routes will try to avoid these.
Turbulence on private jets
Private jets fly higher than commercial jets – Boeing and Airbus fly on average at 35,000 – 40,000 feet. Business jets generally fly at 41,000 – 50,000 feet where they are less susceptible to air pockets and severe turbulence, as well as a more direct route. However, the reduced weight of private jets can mean the same amount of turbulence would feel worse than if you were on a 747 jet. Private jets can also be more flexible with their flight routes in comparison to commercial flights, so if bad areas of weather are spotted, the route can be altered to avoid a turbulent journey.
Is turbulence becoming more common?
With global warming affecting weather patterns across the globe, scientists say that events of turbulence could increase in severity by 10% to 40% by 2050. A 2007 study found that instances of clear-air turbulence over North America and Europe increased between 40% and 90% from 1958 to 2007.
