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II. Operating Characteristics
The fully automatic operation of the AEROMATIC propeller eliminates the use of any controls from the pilot or engine on the model 220. The natural, physical forces acting on the blades and counterweights are utilized to accomplish the desired pitch change. Substantial performance advantages are made possible with the Aeromatic due to the greatly increased propeller and engine efficiencies afforded by automatic operation. Prevention of engine damage as well as maximum operating economy is attained through automatic response to changing conditions of flight.
The airplane-engine-propeller combination has previously been flight tested to determine the proper angular relationship of blade and counterweight arm for any particular C.A.A. approved installation. This setting is held permanently by the use of the counterweight arm clamping action around the blade flange and blade ferrule. A counterweight arm locating screw passes through this entire assembly to insure the proper reassembly when the propeller has been disassembled.
Models 220-1 and 220H are modified versions of the Model 220 with Aeromatic Hi-Cruise control assemblies. The model 220-1 Hi-Cruise control is actuated manually through a control cable and bell crank.
The Model 220H Hi-Cruise pitch change mechanism is actuated by a hydraulic cylinder, which is operated by engine oil pressure controlled through a special control valve.
The Hi-Cruise control unit permits a selective pitch change range of several hundred RPM. This feature is of exceptional value when the airplane is flown at altitudes above 5000 feet. This feature also permits the choice of using the propeller as a standard Aeromatic or as a selective RPM propeller.
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