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How it Works: Speed brakes

How to stop on a dime, or at least a dollar

Speed brakes increase drag, and why would you want to do that? There are few times when more drag is a good thing. One of those times is when you want to descend more quickly, or descend with power so that you won’t shock-cool the engine. Taking an engine from hot in cruise to ice-cold during a long, low-power descent is generally frowned upon. That’s the sort of thing that can crack engine parts.
How it Works
Zoomed image
Speed brakes open like a Swiss army knife to create a little wall above the wing, increasing drag.
Illustration by Steve Karp

The answer is to stick something up in the air stream and increase drag. Even small devices only a few inches across can do the job. Speed brakes on a Mooney made by Precise Flight of Bend, Oregon, under the trade name SpeedBrakes are raised using a switch on the yoke that triggers a solenoid and activates electric motors to raise small, flat surfaces above the wing to form a tiny wall.

They don’t reduce lift the way spoilers do. Spoilers are those surfaces on the top of airliner wings that “spoil” lift as well as increase drag during descents and landing. They reduce lift on a small portion of the wing. Speed brakes affect only drag.

New to the airplane? Can’t get slow enough on downwind in your high-tech, 200-knot dream machine? Time to hit the speed brake switch to help slow the aircraft or increase descent—or both.

Alton Marsh
Alton K. Marsh
Freelance journalist
Alton K. Marsh is a former senior editor of AOPA Pilot and is now a freelance journalist specializing in aviation topics.

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