Sep 18, 2024
Listed as one of the leading causes of in-flight injuries to crew and passengers according to Australia’s Civil Aviation Safety Authority, turbulence is a complex phenomenon present in various aspects of nature but is most commonly encountered by people during air travel. For those who find themselves a little anxious about aircraft turbulence, let’s explore its causes, when turbulence is likely to occur and how pilots and aircraft are equipped to handle it.
What Is Turbulence?
Whether it’s a few bumps here and there or severe enough to cause significant damage, turbulence is most certainly unpredictable and sometimes frightening. It is, however, quite a common occurrence during air travel.
Turbulence can be more accurately described as a series of abrupt sideways and vertical shifts in the aircraft position due to the presence of “irregular atmospheric conditions”, most often caused by changes in air pressure, weather patterns or temperature.
Turbulence does not affect every aircraft to the same degree; larger, heavier aircraft are not as susceptible to air variations because they require more energy (from the turbulence) to cause them to change their attitude (pitch, yaw, and roll) or straight and level flight.
Where Does Turbulence Most Commonly Occur?
While irregular in nature, the ideal conditions for encountering turbulence are much easier to predict especially for pilots who study atmospheric conditions and weather-related events before and during flight.
This is because most turbulence occurs when there is a combination of up and down drafts of wind, such as in clouds, over high mountains, across large bodies of water, around the equator and when entering/crossing jet streams. High humidity and temperatures also tend to make turbulence stronger.
Although technological advances are improving in the area of turbulence detection, it is currently impossible to accurately predict where and when turbulence will occur in every instance or how severe it will be.
What Causes Aeroplane Turbulence?
There are a number of factors that contribute to turbulence encountered during flight, let’s take a look at the common types of turbulence while in an aircraft.
- Clear Air Turbulence (CAT). The most challenging type of turbulence, Clear Air Turbulence occurs in clear skies, most commonly at altitudes above 15,000 feet. This type of turbulence is caused by the interaction of different air masses moving at different speeds, it is not visible and usually cannot be detected by conventional radar systems. An example of Clear Air turbulence might be when encountering high-altitude air rivers known as jet streams.
- Thermal Turbulence (Convective). Thermal turbulence occurs as a result of uneven temperatures on the Earth’s surface. These hot spots (sandy areas, rocky terrain, cities, etc.) build pockets of warm air. Because warmer air naturally rises and cool air descends, this creates upward currents of warm air that interact with the regular air/wind currents causing “thermals”. As aircraft fly through thermals, experiencing turbulence is highly likely, so much so that many pilots of smaller aircraft prefer to fly either in the early morning or late afternoon to avoid increased thermal activity during the hottest part of the day.
- Mechanical Turbulence. When air encounters large obstacles or terrain features that disrupt the regular airflow like mountains or buildings, turbulence can build as it creates eddies and irregular air patterns. Stronger turbulence will be experienced when flying through unstable air over rough terrain with high wind speeds.
- Mountain Wave Turbulence. As the name suggests, Mountain Wave turbulence usually occurs across mountain ranges. It is caused by strong winds passing over the rough terrain, causing unusual disturbances in the air, which can last for several hundred kilometres downwind of the mountain. Put simply, as wind hits the mountain ridges, the resulting waves of air form unusual patterns due to the interaction between unstable air on the windward side and stable air on the lee side of the mountains. This dangerous combination can result in strong updrafts on one side and equally strong downdrafts on the opposing side.
- Wake Turbulence. Wake turbulence is generated by the aircraft itself or other nearby aircraft. Much like we experience when travelling in a car, aeroplanes disrupt the air as they move through it, this creates vortices from the wings, which can disturb other aircraft in close proximity to each other. Smaller planes are more vulnerable when getting caught in the wake of larger aircraft.
- Thunderstorm Turbulence. Convective activity within thunderstorms (and around them) can be quite severe resulting in violent updrafts and downdrafts. Pilots should always avoid flying through or near thunderstorms because of the extreme turbulence-related danger.
- Frontal Turbulence. Frontal turbulence is due to weather conditions, usually the interaction of cold and warm air masses (fronts). Friction occurs at the junction between the two due to their temperature and density differences. The mismatch between the two fronts creates turbulent conditions while flying from one air mass to another.
How Dangerous Is Turbulence?
The good news is pilots are well trained, and the aircraft they fly are designed to be able to handle even the worst turbulence, so it is highly unlikely turbulence will cause significant damage, however that doesn’t mean structural damage isn’t a possibility under extreme circumstances.
Although relatively rare, the violent nature of severe turbulence has been known to throw passengers and crew around the cabin, causing injuries to the head and neck, along with other soft tissue injuries and broken bones. This is why pilots try to mitigate the effects of turbulence on the aircraft by doing their best to avoid it or by slowing down below their designed manoeuvring speed. Decreasing speed helps reduce the aircraft’s load limits, which can lead to structural damage if exceeded.
How Common Are Turbulence-Related Injuries?
Turbulence encounters that cause minor injuries are relatively common throughout the world, however fatalities are very, very rare. It is difficult to put an exact number on the turbulence-related injuries in New Zealand as these incidents are quite rare. However, if we look to the US for a rough idea of the stats, the National Transportation Safety Board of America reported that between 2009 and 2022, 163 people were injured and required hospital treatment as a result of turbulence.
Common injuries caused by turbulence on commercial airline flights:
- Soft Tissue Injuries. Sudden changes in altitude can cause a number of soft tissue inquiries related to the rapid movement of the aircraft. Twists and strains of knees and ankles are typical.
- Falls. If standing or walking in the aisle when turbulence strikes, passengers can be thrown to the floor, fall sideways onto other passengers or bump into trolleys, walls, seats, or doors.
- Head/Neck Injuries. Neck strain or whiplash, hitting heads against ceilings, seat backs and windows, items falling from overhead compartments.
- Broken Bones. Severe turbulence can cause such swift movements that people can be thrown with such force that they may break bones, typically arms, legs, feet, and hands.
Can Pilots Avoid Turbulence?
While it’s not possible to completely avoid turbulence all of the time, there are a number of tools pilots can use to aid in steering clear of the worst of it. A weather radar display/aviation forecasts are useful for avoiding obvious meteorological situations, this enable them to detect and fly around/above/below things like thunderstorms. Awareness of how large obstacles across the flight path might affect wind flows, such as a high row of trees, and natural ridges, and how they might disturb wind flow also helps.
Monitoring jet streams along the route for signs of wind shear and altering the flight path to fly around those areas is another helpful tool. Air traffic controllers can also provide warnings to pilots when other planes have run into turbulence in the area. Avoiding clear-air turbulence is the hardest and almost impossible which is why it can be the most devastating often catching people (and pilots) dangerously off-guard.
Is Turbulence Becoming More Frequent?
Some evidence is emerging that it is believed turbulence is becoming more common, possibly due to the impacts of climate change and the associated effects on the planet and its weather patterns, but taking into account people are flying about much more than at any time in the past is also an essential factor to consider.
More flights mean more aeroplanes in the sky at any one time, which could make a pilot’s decisions in avoiding turbulence more challenging (maintaining safe minimum distances from other aircraft in the area might take precedence), and could also mean encountering wake turbulence is more common.
What Can Passengers Do To Stay Safe?
Keep your seat belt on! This is the number one thing passengers should remember when staying safe during any short or long haul flight. Other things to keep in mind are avoiding having any loose heavy objects around you (luggage, etc.), ensuring your seat belt is fastened correctly (low around the hips) and listening to (and following) all crew instructions!
Encountering turbulence is a natural part of air travel, having a better understanding of what turbulence is and what causes it can help demystify the experience, alleviating anxiety and increasing flight safety. And remember, whether it’s clear air turbulence or the more predictable thermals, pilots are well-trained to handle the challenge!