Pilot's Corner: Turbulence and Storm Dodging

DALLAS — The primary responsibility of a pilot is to ensure the safe and efficient transportation of their aircraft and passengers to their intended destination, adhering to the scheduled arrival time, and minimizing any incidents.

Passengers generally dislike turbulence, as it causes discomfort and can be a significant source of anxiety, particularly for nervous flyers. There are four main types of turbulence:

Clear-air turbulence: This type of turbulence occurs when large air masses of high or low pressure collide or when encountering high-level jet streams. Clear-air turbulence can be avoided by planning flight routes that steer clear of these areas.
Wake turbulence: Flying in the wake of a preceding aircraft that has disturbed the air generates wake turbulence. Consider the visible wake left by a large boat. To avoid wake turbulence, aircraft maintain lateral separation, fly at different altitudes, or offset their tracks.
Mechanical turbulence: Strong winds passing over mountains cause mechanical turbulence. This generates waves of turbulence that can reach up to five times the height of the mountains and extend for hundreds of miles, depending on wind strength. Planning flight routes around mountainous areas or regions prone to this type of turbulence can prevent encountering it.
Weather-related turbulence: Weather-related turbulence occurs in the presence of cumulonimbus clouds, commonly known as thunderclouds. These large, white, puffy clouds can grow in width and height, often surpassing the normal cruising altitude of airliners. To avoid weather-related turbulence, pilots choose to fly around these clouds or delay take-offs and landings if they directly impact the airport.

Cumulonimbus Clouds

Cumulonimbus clouds contain powerful vertical shafts of air and moisture. Rising air (updrafts) lifts huge amounts of moist air into the atmosphere, which condenses to form these clouds.

When the interior of the cloud becomes completely saturated, it forms rain and hail, which fall within the cloud, causing large downward shafts of air (downdrafts). The combination of multiple updrafts and downdrafts within the cloud is what will cause light, moderate, or severe turbulence.

During the day, we can see these clouds from hundreds of miles away and plan an alternative route around them, but what about at night?

Radar Signals

Updrafts and downdrafts within a cloud are not visible, but we know that downdrafts contain water in the form of rain or ice. To detect these atmospheric conditions, aircraft radar systems emit powerful radio beams ahead of the aircraft. If these beams encounter an obstacle, such as water particles, they are reflected to the radar. The strength of the reflected signal indicates the concentration of water.

By measuring the time it takes for the signal to return, the radar can calculate the distance to these various reflections. The concentration of water particles is then displayed on the navigation display (ND) as green (light), amber (moderate), or red (severe). If the distances between these indications are close, it may indicate the presence of extreme turbulence, which is depicted in magenta.

The radar systems on Airbus A350 aircraft are highly advanced, continuously scanning the sky ahead, above, and below the aircraft. The radar returns are displayed both in a horizontal view and a vertical view, providing information about clouds located above or below the aircraft's cruising level.

If the flight route takes the aircraft above storm clouds, this is indicated on the display with a "hatched" pattern, serving as a reminder that the aircraft will be passing over a convective cloud and may experience mild turbulence. By navigating around areas indicated as green, amber, and especially red on the display, passengers can enjoy a smooth and relaxed journey without any spillage of their drinks.