Historical
SAE ARP 493A-2002 (SAE ARP493A-2002)
Knobs, Control Aircraft, Recommended Design
The purpose of this document is to recommend shapes and sizes of knobs which will guide the design of these components toward eventual uniformity. This recommended practice is intended to recommend the basic shapes and dimensions for knobs used in aircraft. Two basic types of knobs, the bar shape and the round shape, are described, as well as several widely used variations of these two basic shapes.
Society of Automotive Engineers [sae]