One of the most curious systems was the Ratier prop fitted to the (ahh) de Havilland DH-88 Comet. A 2-speed prop which was set to fine on the ground by pumping up a football bladder type thing with a bicycle pump. As the speed increased, airflow on the spinner moved a deflation valve and the prop pitch moved to the coarse setting.....
A couple of problemos with that:
1. Both props didn't always coarsen at the same time.
2. Go-arounds would have been rather exciting.......
