More info from a swift web page: The F200 Aeromatic "Propeller with a Brain" variable pitch propeller was included on the Swift type certificate as a factory option. An ingenious mechanism in the hub of the Aeromatic uses a combination of centrifugal twisting moment and aerodynamic forces to establish optimal pitch without pilot input. Aeromatics acquired a dubious reputation for their tendency to discard their wooden prop blades in flight. This could usually be traced to poor maintenance. particularly on aircraft kept in freezing weather. Wood has desirable vibration characteristics as a propeller material, but requires more care than metal. The Aeromatic is an example of a variable pitch but not controllable or constant speed propeller.
The Beech-Roby controllable pitch propeller was also a factory option. This propeller, also wooden, used a hand crank and driveshaft from the instrument panel to allow the pilot to vary propeller pitch within a given range. It is seldom seen on Swifts and a later metal version, using an electric motor to replace the hand crank, is more commonly seen on early Bonanzas. It can also be found on some Luscombes and Mooney Mites, where it is said to make a real performance difference. It is not constant speed.
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