EAA Sport Aviation - April 2011

away from it as I could get. When I could spare a hand, I cinched down my shoulder harness. It was a really detestable ride and did not ease up for several minutes.

GUST FRONT

I had apparently been hit by a gust front, a phenomenon I’d always associated with thunderstorms. The dynamics of thunderstorms are well described elsewhere, but what matters in this context is that they have violently strong air currents inside them, and the down-going currents, coming from high altitudes, hit the ground and spread out ahead of the storm, sending out blasts of invisible cool air. It’s as if the thunderstorm were an immense leaf blower, clearing unwanted debris (such as airplanes) out of its way. I’d read about them and heard about them from instructors when I first began flight training, but they’d never been mentioned in connection with individual clouds. And I had never been foolish enough to get in front of a line of thunderstorm clouds.

This particular cloud was a loner, its base at maybe 5,000 feet AGL and its top at 8,000, and not quite as well-defined as I’ve drawn it. The cloud had been just big enough, and dark-bottomed enough, to draw my attention, while not so menacing as to make me turn and skedaddle directly away from it. Not until I got hit.

So it appears that it’s not only thunderstorms that have gust fronts, or something enough like gust fronts. The winds that came out of this particular cloud were not noticeably cold, but maybe that was because it isn’t that cold at 8,000 feet. An actual gust front from an actual thunderstorm might have been violent enough to tear the airplane apart. This one was only bad.

BACK TO BASICS

Let’s review some of the fundamentals of turbulence: It has many causes, starting with rising and descending air currents. This is basic stuff, but worth describing. Almost any time the sun is shining, it will heat the ground, and the air near the ground eventually gets

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