# For a rotor in vertical autorotation, what is the relation between pitch, vertical speed and rpms?

In other words, what happens to vertical speed and rpms in vertical autorotation if I change the pitch of the blades of the gyro I use to fly...?

• Please forgive a perhaps stupid question, but doesn't autorotation imply zero thrust? – user Dec 7 '17 at 11:42
• No. You have a thrust exactly as the weight of the gyro. That's why it descends (in vertical autorotation) with a constant speed, and not accelerating... Thanks to your answer, I've now realized that the thrust is constant, so I'm now editing the question, changing 'thrust' with 'vertical speed' – xxavier Dec 7 '17 at 11:52
• The fact that it descends with a constant speed does not mean it provides thrust. A falling feather descends at constant speed too. When a helicopter autorotates, it converts potential energy (height) into rotational kinetic energy (gaining rotor rpm). When it flares to land smoothly, it transforms kinetic energy of the blades into thrust or lift. (bleeding rotor rpm) – qq jkztd Dec 7 '17 at 12:30
• @qq jkztd Wrong again... There are two annular zones in the autorotating rotor, the driven one (which overcomes most drag and produces most lift) and the driving one (that absorbs energy from the upward-flowing air, converting it to power to drive the rotor). Both zones produce thrust, if it's true that the driven one (the outward ring) is responsible for most of it. – xxavier Dec 7 '17 at 13:25
• @xxavier Please also consider giving the same advice to the person who illustrated this ,since it doesn't fit to your understanding of elementary physics concepts. – qq jkztd Dec 7 '17 at 15:25