For most air travelers, turbulence is a word that invokes at least a little dread and discomfort. However, in most cases such apprehension is at least partly due to fear of the unknown. Once we better understand the subject, our newfound knowledge can help allay unnecessary anxiety. With this series of posts, we’ll examine the causes of turbulence and methods for avoiding and mitigating any encounters.
In this post, we’ll examine the types of low-level turbulence. Low-level turbulence includes all forms of turbulence found below an altitude of approximately 15,000 ft. Regardless of your flight’s eventual cruise altitude, all aircraft must pass through these lower levels after departure and prior to arrival at the destination airport. At times, certain low-level turbulence is unavoidable and is best handled when properly understood.
Roughly defined, turbulence is an irregular motion of the atmosphere. Mechanical turbulence is caused by terrain, buildings, or other structures disrupting the smooth airflow through a given area. This type of turbulence is most commonly encountered during takeoff and landing when hills, ridges, or infrastructure around the airport interfere with the flow of surface winds. Based on their surroundings, some airports are more susceptible to mechanical turbulence than others. When encountered, mechanical turbulence only lasts for a few minutes and will dissipate after landing or once climbing a few thousand feet upon takeoff.
Commonly referred to as thermals, convective turbulence is generally associated with warm weather. This turbulence is caused by solar heating reflecting upwards off the surface. The higher the temperature, the stronger and higher you can expect the thermals to be. When sufficient atmospheric moisture is present, cumulus clouds tend to denote the upper extent of thermals. As with mechanical turbulence, convective turbulence is limited to within a few thousand feet of the surface and will only be experienced during takeoff and landing.
As the name implies, frontal turbulence is typically found ahead of a fast-moving cold front. You can anticipate frontal turbulence by watching the weather before your planned departure. If a cold front is approaching your departure or destination airport, you might encounter some frontal turbulence. En route, such encounters are generally not an issue, as frontal turbulence is most common at lower altitudes. However, if you’ll be cruising at low altitude (on commuter aircraft or short legs), it’s possible you’ll encounter this turbulence in cruise. In such cases, the pilots, dispatchers, and air traffic controllers (ATC) can often coordinate to avoid the most probable turbulence areas.
Though categorized as a form of turbulence, wake turbulence is generated by aircraft, not the atmosphere. While all aircraft generate some turbulence as a result of lift, the strongest wake turbulence is produced by heavy aircraft during takeoff and landing. To combat wake turbulence, ATC maintains minimum separation distances between aircraft. On the ground, aircraft are sometimes required to hold for a few minutes to allow wake turbulence to dissipate. Additionally, pilots can request additional separation/hold time if they judge it’s in the interest of safety. Due to the wake turbulence avoidance procedures used by pilots and ATC, your chances of encountering wake turbulence are extremely rare.
What can you do?
As a passenger, your best defense against low-level turbulence is knowledge of its characteristics. By referring to the information above or researching the topic on your own, you’ll be better prepared for possible low-level turbulence encounters. In many cases, your knowledge of when, where, and how long turbulence is likely can go a long way to relieving any anxiety about an encounter. During flight, try to remain seated with your seatbelt fastened. Secure your personal items to the extent possible and keep a hand on any foods and drinks, particularly hot items. If a trip to the restroom is necessary, try to go before entering or after exiting expected turbulence zones.
In a future post, we’ll discuss other forms of turbulence and identification/planning/avoidance methods used by pilots and ATC. Don’t let a chance encounter with turbulence keep you from enjoying your time aloft. The more you understand its causes, the better you’ll enjoy your flight.