On the hour vs E6B Slide Rule

Just one feature: Chime on the hour

This simple circular slide rule works the way your aviator watch does. For rate/time calculations it can be faster than a calculator: set the rate once and read every distance and time straight off the dial, without typing anything. If you're an aviator who would rather use a slide rule than a calculator, try this app. It is much easier than trying to punch numbers on a watch calculator. We created it for the watch, but it works on the iPhone and iPad, too. Rotate the outer ring with your finger or with the Digital Crown. Let go mid-turn and it spins on and coasts to a stop. Slow down and the crown gets finer under your finger, so you can settle exactly where you meant to. A click marks each numbered graduation passing the rate index — feedback only, never a detente, so the dial will never nudge you onto a mark you did not choose. THE FACE Three concentric logarithmic scales, drawn to the proportions of the real thing. • The outer scale carries rate, distance, fuel and quantity, and it is the ring that turns. • The minutes scale sits inside it, fixed, with the rate index locked at twelve o'clock. The one pointer you read everything against never moves. • The hours scale runs 1:00 to 10:00 beneath, so elapsed time reads directly without converting from minutes. Complications on the watch face open it in one tap. Where you left the dial is where you find it, for a day. On iPhone and iPad it's the same instrument, larger, with room for numerals the watch has to leave off. WHAT IT DOESN'T DO: There's no keypad and no equals key — you read the answer off the dial, the way the instrument is meant to be used. No network: the app has no reason to reach the internet and never does. Nothing is collected, nothing is tracked, and nothing leaves your device. A reference and training tool. Not a certified flight computer — verify critical calculations independently.