This popular computer from Aero Products Research will solve time, speed, and distance problems for anything from a light aircraft up through a Mach-2 fighter. Also easily calculates compressibility and temperature rise corrections. Wind solutions are graphically displayed. Since it's all mechanical, you never have to worry about batteries going dead at an inopportune time! This durable plastic computer comes with a vinyl case and a fully illustrated manual. We offer two versions of this computer. This is the 6-inch diameter "navigator" model, where the large size enhances readability. We also carry a 3-inch diameter "shirt pocket" version (available in a separate listing) which is identical, except that it's half the size to maximize portability and ease of storage in a tight cockpit (the 3-inch version is popular with sport aircraft pilots).