PASSIVE PROPELLER CONTROL

VERY-HIGH-ALTITUDE, LONG-ENDURANCE (VHALE) TYPE AIRCRAFT OPERATE OVER A WIDE POWER RANGE DUE TO ALTITUDE AND FUEL LOAD CHANGES. MATCHING THE PROPELLER TO THE ENGINE OVER THIS RANGE IS DIFFICULT WITHOUT A COMPLICATED VARIABLE-PITCHPROPELLER OR GEARING. PASSIVE, OPTIMAL-PITCH CONTROL IS THEGOAL OF THIS PROJECT. THE CONCEPT CONSISTS OF AN AERODYNAMICALLY TAILORED BLADE, BALANCE WEIGHTS, AND TORSIONALLY SOFT SPAR MOUNTED ON THE MAIN PROPELLER SHAFT AND ATTACHED TO THE BLADE AT A POINT NEAR ITS MID-SPAN. THIS ELIMINATES MOST OR ALL OF THE LINKAGES AND BEARINGS NORMALLY NEEDED IN A VARIABLE PITCH MECHANISM, ACHIEVING SUBSTANTIAL WEIGHT SAVINGS AND INCREASED RELIABILITY. THE PROBLEM OF SIMPLE INERTIAL, AERO-ELASTIC CONTROL IS THAT, OVER A WIDE OPERATING RANGE, THE REQUIRED SETTING IS DIFFICULT TO ACHIEVE PASSIVELY. A METHOD FOR THE MULTI-POINT OPTIMAL DESIGN OF PASSIVE PITCH CONTROL PROPELLERS THAT DEALS WITH THE MATCHING PROBLEM WILL BE APPLIED. THE TASKS INCLUDE DETERMINING DESIGN REQUIREMENTS,DEVELOPING A COMPUTER DESIGN METHOD FOR THE BLADE PITCH DYNAMICS, EXERCISING THE METHOD TO DESIGN A SPECIFIC PASSIVE-PITCH PROPELLER MECHANISM, AND EVALUATING AND DOCUMENTING THE MERITS OF THIS CONCEPT. VERY-HIGH-ALTITUDE, LONG-ENDURANCE (VHALE) TYPE AIRCRAFT OPERATE OVER A WIDE POWER RANGE DUE TO ALTITUDE AND FUEL LOAD CHANGES. MATCHING THE PROPELLER TO THE ENGINE OVER THIS RANGE IS DIFFICULT WITHOUT A COMPLICATED VARIABLE-PITCHPROPELLER OR GEARING. PASSIVE, OPTIMAL-PITCH CONTROL IS THEGOAL OF THIS PROJECT. THE CONCEPT CONSISTS OF AN AERODYNAMICALLY TAILORED BLADE, BALANCE WEIGHTS, AND TORSIONALLY SOFT SPAR MOUNTED ON THE MAIN PROPELLER SHAFT AND ATTACHED TO THE BLADE AT A POINT NEAR ITS MID-SPAN. THIS ELIMINATES MOST OR ALL OF THE LINKAGES AND BEARINGS NORMALLY NEEDED IN A VARIABLE PITCH MECHANISM, ACHIEVING SUBSTANTIAL WEIGHT SAVINGS AND INCREASED RELIABILITY. THE PROBLEM OF SIMPLE INERTIAL, AERO-ELASTIC CONTROL IS THAT, OVER A WIDE OPERATING RANGE, THE REQUIRED SETTING IS DIFFICULT TO ACHIEVE PASSIVELY. A METHOD FOR THE MULTI-POINT OPTIMAL DESIGN OF PASSIVE PITCH CONTROL PROPELLERS THAT DEALS WITH THE MATCHING PROBLEM WILL BE APPLIED. THE TASKS INCLUDE DETERMINING DESIGN REQUIREMENTS,DEVELOPING A COMPUTER DESIGN METHOD FOR THE BLADE PITCH DYNAMICS, EXERCISING THE METHOD TO DESIGN A SPECIFIC PASSIVE-PITCH PROPELLER MECHANISM, AND EVALUATING AND DOCUMENTING THE MERITS OF THIS CONCEPT.