Have you experienced or been afraid of bumps in the sky while flying? Do clouds cause bumps when flying through them? In this post, we share some of the causes of in-flight turbulence and clear misconceptions that you may have regarding turbulence. But first: what causes turbulence? We will look at four types of turbulence and we trust that you would have cleared your misconceptions at the end of this blog post. Types of turbulence include thermal turbulence, mechanical turbulence, jet streams and wake turbulence.
- How to overcome the fear of flying.
- 5 ways to make flight training enjoyable.
- What to do when lost in flight.
- Buckle up: Always ensure that you are seated upright and that your seat belt is properly fastened. This will ensure that you will remain restrained in the event that the aircraft enters an uncommanded roll, or when the pilots initiate an emergency climb or descent.
- Pack up: Ensure that all baggage is stowed to protect yourself and others from flying projectiles that can cause injury.
- Look up: Ensure that you have taken note of emergency exits for easy evacuation in the event of an emergency landing.
- Cheer up: Fear will not cause turbulence to stop. Instead, it will reduce your chances of survival in an emergency. Sober up and accept the fact that the pilots are trained for the job and will do everything possible to ensure a safe outcome.
You can expect thermal turbulence in summer or on a hot day. During the day, as the sun is heating the earth’s surface through a process that is technically known as insolation (solar irradiation); the uneven earth’s surface gets warmer differently. The air near the earth’s surface rises up as it gets warmer and is replaced by cool air which eventually gets heated up as well and rises. Because warm air is less dense than cool air, this causes uneven convective currents. Factors that affect insolation include cloud cover and the surface being heated among others. For example, ploughed fields absorb more insolation (heat) than grass fields. On the other hand, water will absorb heat on a slower pace than land but will retain heat much longer.
When air passes over irregular terrain such as mountains or man-made obstacles such as buildings, there is friction with the obstacle and its flow is disturbed. This air tends to flow round and up that obstacle because air naturally wants to pass through an area of least resistance. This disturbance is called mechanical turbulence and causes bumps to low-flying aircraft over that area. You can thus expect mechanical turbulence when flying low above mountains or buildings.
These are narrow bands of strong winds in the upper levels of the atmosphere that blow from west to east. They are caused by both solar radiation and coriolis force. Polar jets are the strongest jet streams and are found in the polar regions. Subtropical jets which are weaker are often found at 10–16 km (33,000–52,000 feet) above sea level. Small aircraft like the one on our training fleet can only go as far as 15,000 feet so you cannot expect to encounter jet streams due to the fact that they do not go as high as that altitude.
When turbulence is caused by other aircraft, it is called wake turbulence. It is the one that is particularly dangerous to the aircraft that is behind the wake-generating aircraft. An aircraft hit by wake will typically go into an uncommanded roll and if close to the ground, its trouble.
How do pilots avoid wake turbulence?
To prevent accidents arising from wake turbulence, the International Civil Aviation Organisation (ICAO) has classified several aircraft wake turbulence categories according to their weight. In practice, air traffic control (ATC) utilises both time and radar (distance) to separate aircraft from following each other too closely to protect the following aircraft from encountering wake turbulence. If an aircraft is following another too closely and there is risk of wake turbulence, ATC will issue the warning “caution wake turbulence” to the following aircraft. The fine details are of course part of the training that our students go through so we will not discuss them here in the interest of space and time.
When it comes to thermal turbulence, pilots avoid it by rescheduling flights. For example, flying early morning or late afternoon will lower chances of thermal turbulence. If rescheduling is not possible, pilots fly above the clouds. This is because thermal turbulence is more intense when flying close to the ground.
Are pilots afraid of turbulence?
No, not at all. Pilots are trained to handle turbulence by among others reducing speed during a wake encounter to avoid overstressing the aircraft. In itself, turbulence is not dangerous. Statistics show that no aircraft has crashed due to turbulence. Of course wake turbulence is what every pilot is careful and concerned about because it has been responsible for a few fatal crashes.
How to be safe in turbulence
There are several things that you could do to stay safe during flight in turbulent air. We will share a shortlist of the tips that are recommended by industry experts.