Originally Posted by johnin

It's my understanding that the term "spoiler" comes from its use in aviation, where it is used to "spoil" the lift of an airfoil. Sailplanes use them and so do airliners - look out the window next time you fly somewhere - see those flat pieces of metal that pop up from near the trailing edge of the wing just after landing? Those are spoilers - "spoiling" the lift of th wing puts the weight of the aircraft on its wheels so the wheel brakes can be more effective and the pilot has better control. Those structures on top of tractors look like fairings to me - so called because they "fair" the airflow thus reducing drag. And what should we call the flat pieces of something - plastic? fiberglass? - that are appearing on semi-trailers hanging down along the sides between the tractor wheels and the trailer wheels? They wouldn't be there if they didn't do something useful - reduce drag seems like the most logical thing - to increase fuel economy.