A controllable-pitch propeller rotates each blade about its root axis while the hub turns. This calculator linearly interpolates between two entered pitch-angle endpoints using an entered normalized actuator position.
Variable Pitch Propeller Interactive Calculator
Enter an abstract actuator position and fine/coarse pitch endpoints. Results are an arithmetic interpolation—not a calibrated piston-to-blade law, thrust prediction, governor model or propeller rating.
Equation Used
- Piston position is treated as an abstract normalized coordinate from 0% to 100%.
- Blade angle is assumed to interpolate linearly between the two entered endpoints.
- All blades are assumed to share the same commanded angle.
- Pitch reference radius, handedness and angle datum are not established.
- Actuator geometry, backlash, stops, hydraulic pressure, centrifugal and hydrodynamic loads, governor response, thrust, torque, power, stress, wear and safety are omitted.
Documented Controllable-Pitch Topology
U.S. Patent 2,945,542 documents blade-root mountings rotatable in a hub and a hydraulic piston connected by links to change pitch. U.S. Patent 6,261,062 likewise documents pivotally mounted blades and hydraulic actuation, while describing multiple possible mechanical linkages between an axially moving piston and blade pedestals.
The animation illustrates a generic piston, yoke and blade root. Dimensions, stops and linkage calibration must be established for the particular propeller.
What This Calculator Represents
The tool maps an entered 0–100% position linearly between two entered pitch-angle endpoints. It reports the interpolated angle, the change from the fine endpoint and the endpoint span.
Entered-endpoint Pitch Interpolation
interpolated beta = beta_fine + (p/100) Delta beta
change from fine endpoint = beta - beta_fine
No propeller coefficient, diameter, speed, fluid density or advance speed is present, so thrust and torque are not calculated.
Worked Arithmetic Example
For entered endpoints 10° and 35°, the span is 25°. At position 100%, interpolated pitch is 35° and change from the fine endpoint is 25°. At 40%, interpolated pitch is 20° and the change is 10°.
Model Boundary
- Calculated: linear interpolation and endpoint differences.
- Illustrated: generic hydraulic-piston, yoke and rotating blade-root topology.
- Not calculated: actual actuator calibration, pitch datum, blade synchronization error, thrust, torque, power absorption, governor behavior, pressure, loads, stress, fatigue, leakage, failure response or safety.
Frequently Asked Questions
Does piston position always map linearly to blade angle?
No; linearity is an explicit calculator assumption.
Is the output a measured blade angle?
No.
Does the calculator predict thrust?
No.
Are hydraulic pressure and actuator force included?
No.
Does it model a constant-speed governor?
No.
Can it rate or approve a propeller system?
No.
References
- U.S. Patent 2,945,542, Controllable pitch propeller: rotatable blade-root mountings, hydraulic piston and links.
- U.S. Patent 6,261,062, Actuation system for a controllable pitch propeller: pivotally mounted blades and hydraulic actuation topology.
- FAA, Aviation Maintenance Technician Handbook—Powerplant, propellers: governor oil, hydraulic piston and blade-angle control.
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