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About this Article
Written by: George Sechrist
Written on: October 30th, 2002
Tags: aerospace engineering
Thumbnail by: Starr/Wikimedia Commons
About the Author
At the time of publication, George was a senior undergraduate student majoring in Industrial Engineering at the University of Southern California. He enjoys constructing and flying remote controlled airplanes.
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Volume I Issue IV > Dynamic Soaring
Dynamic soaring is a specialized form of gliding flight that has not yet been thoroughly researched. Observations of the albatross seabird show that it is possible to harness abundant energy by flying specific patterns through a boundary layer between two layers of air with differing wind velocities. Prior to the 1990's, rigorous examinations of these behaviors were left undone because powered flight and the use of thermals were safer to use. Only recently has research been able to verify physical theory by collecting data using remote controlled sailplanes. The data collected thus far demonstrates how the albatross is able to sustain long flights without flapping its wings and gives insight on the limits of dynamic soaring.

The Albatross

Early observations of dynamic soaring in literature occur as early as the 16th century. Coleridge's poem Rime of the Ancient Mariner is about a sea bird called the albatross that possesses God-like status because it could fly long distances effortlessly [1]. In the 16th century, there was no documented discussion of how albatross were able to produce the energy to perform such a feat without flapping their wings (Figure 1). Today, with an advanced understanding of the aerodynamics and mechanics of bird flight, scientists and engineers have developed concepts that explain how the albatross and other birds are able to harness energy by flying through the boundary layer between slower moving air and faster moving air, which is known as dynamic soaring.
Starr/Wikimedia Commons
Figure 1: Albatross flight patterns provide valuable insight on dynamic soaring for aerospace engineers.

Key to Dynamic Soaring

In a posted correspondence, aerospace engineer Blaine Rawdon explained that dynamic soaring requires air to move in a particular way: a steady strong wind moving along a surface. This results in a variation in wind speed called a wind gradient, where the wind speed varies with altitude. The gradient is strongest near the surface and diminishes gradually with altitude [2]. The air closest to the surface will move slower than the air farther away due to a frictional force between the surface and the wind, an effect that can be observed on breezy days. Branches on tall trees sway in the wind, but at ground level far less wind is felt. This happens because the ground is slowing down the air closer to it. Traveling in and out of different wind speeds in certain patterns has the potential to provide extra energy. Flying in the correct pattern is the key to dynamic soaring.

Basic Pattern to Dynamic Soaring

  1. Fly at a height where the wind is traveling faster then it does at ground level
  2. Dive down to the ground level increasing your speed (due to gravity)
  3. Turn 180 degrees and travel into the wind, flying against the ground level wind speed.
  4. Turn 180 degrees and using the speed of the wind; climb back up to the previous altitude gaining speed.