Several designs were tried, including a small bladder of pressurized air in the propeller hub providing the necessary force to resist a spring that would drive the blades from fine pitch (take-off) to coarse pitch (level cruising). At a suitable airspeed a disk on the front of the spinner would press sufficiently on the bladder's air-release valve to relieve the pressure and allow the spring to drive the propeller to coarse pitch. These "pneumatic" propellers were fitted on the DH88 Comet aircraft, winner of the famed long-distance 1934 Mac Robertson race and in the Caudron C.460 winner of the 1936 National Air Races, flown by . Use of these pneumatic propellers required presetting the propeller to fine pitch prior to take-off. This was done by pressurizing the bladder with a bicycle pump, hence the whimsical nickname "Gonfleurs d'hélices" (prop-inflater boys) given to the aircraft ground-mechanics in France up to this day.