Aircraft Propeller Overspeed Protection Without Blade-Angle Changes
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Solution Overview
Problem
Existing aircraft propeller overspeed protection systems often cause in-flight thrust dissymmetry between healthy and failed propellers by varying blade angle, which can lead to control hazard failures.
Innovation Solution
A method and system that adjusts the propeller speed threshold dynamically based on target propeller speed to rapidly detect overspeed and reduce propeller speed without varying blade angle, using a protection controller to maintain blade angle and bypass the propeller speed controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blade angle is varied to control propeller pitch in response to overspeed, then propeller speed is controlled, but in-flight thrust dissymmetry occurs between healthy and failed propellers
Solution Approach 1:
The patent changes the control parameter from blade angle to propeller speed threshold. By adjusting the speed threshold based on target speed rather than varying blade angle, the system achieves propeller speed control while avoiding the harmful thrust dissymmetry that occurs when blade angle is varied between propellers.
Solution Approach 2:
The patent replaces the hydro-mechanical blade angle control system with an electronic speed threshold comparison system. The protection controller electronically compares actual propeller speed to a dynamically adjusted threshold and triggers appropriate responses, substituting mechanical blade angle variation with electronic speed-based control.
2Device complexity
If a fixed propeller speed threshold is used, then the protection system is simple, but overspeed detection is delayed regardless of flight phase
Solution Approach 1:
The patent introduces dynamic adjustment of the propeller speed threshold based on target propeller speed. The threshold is no longer fixed but adapts to current flight conditions, enabling rapid overspeed detection across all flight phases while maintaining relatively simple system architecture through automated threshold calculation.
Solution Approach 2:
The system implements feedback by continuously monitoring actual propeller speed against a dynamically adjusted threshold that responds to target speed changes. This feedback mechanism enables timely overspeed detection by automatically adapting the comparison criterion to current operational conditions.
3Speed
If blade angle is varied to control propeller pitch, then propeller speed is reduced, but control hazard failures may occur
Solution Approach 1:
The patent replaces mechanical blade angle control with electronic speed threshold-based control. By using electronic comparison and control rather than mechanical blade angle variation, the system achieves propeller speed reduction while eliminating the control hazard failures associated with hydro-mechanical blade angle control.
Solution Approach 2:
The patent changes the control approach from blade angle modulation to speed threshold enforcement. By controlling propeller speed directly through threshold-based protection rather than varying blade angle, the system achieves speed reduction while avoiding the control hazards inherent in blade angle manipulation.
Data Source
AI summary
A method of operating a propeller system for an aircraft. The method includes: receiving propeller speed information, the propeller speed information indicating propeller speed; receiving a target propeller speed; performing a propeller speed threshold adjustment process, the propeller speed threshold adjustment process comprising adjusting a propeller speed threshold as a function of the target propeller speed; comparing the propeller speed to the propeller speed threshold; and in response to propeller speed exceeding the propeller speed threshold, performing an overspeed protection process.