For the second part of our article dedicated to turbulence, we met a pilot with the aim of gaining a better understanding of the phenomenon of in-flight turbulence.
Meeting with Joffrey Dellis, a former military pilot (F16), airline pilot (A330-340-350) and today a business aviation pilot (EAPC) and instructor (NewCAG Aviation School).
Can we go through the different types of turbulence?
Of course, we can! There are 7 different types of turbulence: thermal, wake, mechanical, orographic, storm, pilot-induced (e.g. when using airbrakes) and Clear Air Turbulence (CAT), which forms in and around Jet-streams.
When crossing the Atlantic, for example, a pilot may have to follow Jet-streams along defined daily air corridors that correspond to the fastest routes. If this route follows a winding Jet-stream corridor, the aircraft might encounter turbulence several times on the same journey!
Can we detect turbulence in a clear sky?
There is no way to ‘detect’ it as such, but we can predict it using models and, for instance, Jet-stream speed gradients. These factors can alert us to the intensity of turbulence.
We also have weather maps on the iPad that give us information on areas at risk: icing, thunderstorms, turbulence, etc.
Today, I know that some technology companies are working on the development of ‘lidar’ type devices that can detect turbulence in clear skies. This is good news because aircraft are not currently equipped to detect such turbulence. If a pilot encounters turbulence in flight, it is common courtesy to inform his fellow pilots by radio and through air traffic control. Air traffic controllers will then suggest that pilots adjust their flight paths to avoid certain areas.
The turbulence we are talking about in the media today is the so-called ‘severe’ turbulence caused by Clear Air Turbulence (CAT). Television broadcasts images of damaged planes: oxygen masks have fallen off, catering trolleys have shifted, etc. It’s obviously very impressive.
It should be noted that this turbulence has been increasing sharply in recent years, a phenomenon that could be linked to the intensity of the Jet-stream and the increasing temperature differences between the equator and the poles.
Is the pilot informed of the type of turbulence he will encounter during the flight?
Of course, they are! Pilots are given weather charts to help them identify and assess turbulence: small symbols indicate the level of turbulence and the areas where turbulence is likely to be felt. It’s not an exact science, but it allows us to adjust our speed, inform the cabin crew so they can plan the cabin service, and it also allows us to activate the ‘Seat Belt’ signal as a preventive measure. However, I’ve noticed that some passengers play down the safety signals. When the pilot activates the ‘Seat Belt’ signal, you must fasten your seat belt! Inside the aircraft, each passenger is also responsible for his or her own safety…
In today’s more turbulent conditions, the trolleys used to serve meals in the cabin can be a real danger; these angular trolleys, loaded with 80 kg and launched at full speed, can injure the crew and passengers, and damage the aircraft. We need to be vigilant!
How does turbulence affect the aircraft and the flight?
In aviation, maintenance is carried out on a very regular basis. Technicians carry out a complete ‘audit’ of the wear and tear on the structure.
In addition, aircraft are designed to withstand load factors, which means that the aircraft has been tested well beyond those load factors. There is no risk of it breaking up in flight (he smiles).
The same goes for an airplane wing, which is designed and tested (fatigue tests) at loads factors well above than the maximum loads the airplane might experience in flight.
So, I wouldn’t worry too much about the reliability of aircraft, which are very rigorously designed and tested in extreme conditions. I would be more concerned about the passengers who could be injured by turbulence. Such a scenario could force a pilot to make a medical diversion to help the most vulnerable passengers.
Is there a ‘psychosis’ about Clear Air Turbulence?
As a pilot, I’m more afraid of a thunderstorm or a cumulonimbus than I am of Clear Air Turbulence (he smiles).
You also must consider that there is a lot more traffic now than there used to be. So, the likelihood of an aircraft encountering this type of turbulence is greater. Social medias also play an important role in amplifying events, which inevitably contributes to increasing ‘psychosis’.
