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What is eddy dissipation rate?

Updated: Nov 8, 2022

If you are a new pilot or one that has a few thousand hours in your logbook, eddy dissipation rate or EDR is not likely part of your vocabulary. However, if you use the new EZWxBrief progressive web app (visit ezwxbrief.com), you have stumbled across this relatively new "aviation" term. Let's take a look at defining EDR and how it should be used.

When you received your primary training you were likely taught how to deal with turbulence while in flight. That is, you were taught when you are experiencing moderate or greater turbulence, there is a strong need to reduce the velocity of the aircraft to below maneuvering speed or what is sometimes called turbulence penetration speed. Moreover, you were also taught that maneuvering speed is dependent on the weight of the aircraft. The higher the weight, the higher the maneuvering speed. The goal by slowing down is to reduce the forces (or load) on the aircraft parts that could fail as the aircraft accelerates and decelerates in turbulence. Keep in mind that this is less about the wings falling off and more about the engine mount failing.


What is EDR? EDR is an aircraft-independent meteorological field expressed in m²/s³. Simply put, an atmosphere that causes eddies to dissipate rapidly is one that is likely turbulent. Most importantly, EDR is NOT a measure of the likelihood of turbulence as some pilots will make you believe.


In fluid dynamics, an eddy is the "swirling" of a fluid. Given that air has similar properties as a fluid, you can have eddies in the atmosphere. Most pilots have seen pictures of wake vortices swirling off the wingtips of a large turbofan aircraft as it passes through clouds or smoke. Pilots are taught to avoid these wake vortices (which are usually invisible) since they can cause a smaller aircraft following the heavy jet to enter an uncommanded roll. Therefore, this is often referred to as wake turbulence.


In that light, pilots are taught to pay close attention to the wind with respect to wake turbulence. This is because the prevailing current of wind will cause the ed