blimp that needs to do the cyclo thing to stay on the ground, than reverses lift to carry twice the heliums bouancy.
sry for the Google link, I'm on mobile
However, there isn't much information I could find online about this. One of those moments when you wonder if you were taking to someone who slightly misrepresented their government job role.
(I wonder if the submission link shouldn't be replaced.)
Helicopter blade pitch also changes as the blade rotates and it's done mechanically with a swashplate.