A powerless helicopter doesn’t drop—it autorotates, gliding like a maple seed. This breakdown explains how that works, why gyro boats and WWII U-boat rotor kites flew without engines, and how some ...

Most people think a powerless helicopter drops straight out of the sky. In reality, it autorotates—using free-spinning blades that act like a giant air brake, much like a maple seed. This breakdown ...

When Hector Xu was learning to fly a helicopter in college, he recalled having a few “nasty experiences” while trying to navigate at night. The heart-stopping flights led to his research of unmanned ...