Turbulence during the flight of an aircraft is caused by the irregular motion of the air currents that become disrupted by wind shear, weather fronts, thunderstorms, the proximity to mountains, and many other factors. Turbulence is the most common cause of fear and discomfort for airline passengers however, turbulence is usually nothing more than an inconvenience with a few bumps and shaking of the aircraft along the way.
Most pilots are well-trained to handle turbulence and it is rarely severe enough to throw an airplane out of control or to endanger the safety of the flight. Modern aircraft are designed to withstand and absorb turbulent forces so substantial damage to an aircraft from extreme turbulence is very rare.
Turbulence is usually described as light, moderate, severe or extreme depending on the changes in altitude and/or attitude that the aircraft encounters with the turbulence. There are several different types of turbulence and they can affect aircraft differently. The most common types are listed below.
This is the most dangerous type of turbulence and causes the most turbulence-related injuries. It is caused very strong corridors of wind found at high altitudes. It typically occurs in clear skies with excellent visibility, so it cannot be detected by weather radar. The onset is immediate and it does not give the flight crew time to warn the passengers.
Convective turbulence is often associated with the building of clouds as hot air rises from the ground at lower altitudes. They are typically associated with large Cumulonimbus clouds that produce severe thunderstorms. The higher the cloud tops are, the greater the updrafts will be and the turbulence will be at its worst.
Wind is generally affected by friction with the Earth’s surface and any objects on it such as mountains, buildings, etc. The flow of the wind close to the ground is highly disrupted and the variations in direction and speed can cause a high degree of turbulence. This is especially troublesome for aircraft upon takeoff or when the aircraft is on the final approach during landing.
This turbulence is caused by the disruption of the airflow from other aircraft. Wake turbulence typically only occurs for a few seconds, but it can be very violent. Air traffic control typically applies a minimum spacing between aircraft, although some larger aircraft cause more wake than others. The controllers will allow extra space between large and small planes to ensure they are adequately separated from any wake turbulence.
Pilots can avoid turbulence in many cases. Certain types of turbulence can be detected through pre-flight weather reports, by using onboard weather radar, or through information from other aircraft in the area to provide them with the general location that it will be encountered. The pilots can choose to fly through it or avoid the turbulence by choosing the appropriate flight levels or routes to fly around it.
If the pilots know of turbulent conditions ahead, they will turn on the seatbelt sign as the aircraft approaches it to alert the passengers to get to their seat and to ensure their seat belts are fastened.
Each specific model of aircraft has a ‘turbulence penetration speed’ which is its ideal velocity for flying through the turbulence. If the turbulence is unavoidable, the pilots can reduce the speed of the aircraft to that safe velocity so that the aircraft will not be damaged as it passes through the disturbance.
Some aircraft manufacturers are experimenting with lasers attached to the nose of the aircraft that can detect the disruptions in the air patterns and alert the pilots. This can provide the necessary time needed to either avoid the turbulence or to alert the flight attendants and passengers to prevent potential injuries.
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