Measuring and Modifying Wheel Drag – Part 1: Overview
My background now is in aerospace engineering, where landing gear and wheel drag are sort of an afterthought in the academic curriculum (I mean this seriously—it isn't discussed specifically until the last year of the program I recently completed). That's understandable because it is approachable as a combination of areas of study—materials, structures, mass properties, configuration, performance, and aerodynamics. Hoerner includes a short section on landing gear and wheel drag in his Fluid-Dynamic Drag (yes, with a hyphen if you want to look for a copy. His estate still publishes the book, available by special order). After specifying reference area (the simply projected area of the tire as width times height), Hoerner goes through the drag characteristics of various landing gear configurations, fixed and retractable. He also notes something interesting: wheel drag can account for as much as a 50% increase in zero-lift drag or C D,0 on commercial and general aviation ...