Propeller Pitch Actuator Control for Underspeed Mitigation
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Solution Overview
Problem
Aircraft propeller engines face challenges in maintaining optimal rotational speed and pitch angle, leading to failure conditions due to insufficient fluid supply or pressure, which can result in propeller underspeed and increased pitch angles, affecting flight safety and operational costs.
Innovation Solution
A method and system that detect and mitigate failure conditions by commanding actuators to adjust propeller pitch angles and fluid flow, using a flow regulator to maintain fluid pressure and prevent further decreases in rotational speed, and employing a second actuator to hold the pitch angle until the aircraft lands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the propeller control unit commands the actuator to decrease the pitch angle to increase rotational speed, then the rotational speed should increase towards the reference speed, but the pitch angle may fail to decrease or the rotational speed may fail to increase due to actuator failure or insufficient fluid supply
Solution Approach 1:
The controller performs preliminary detection by monitoring whether the pitch angle actually decreases and whether the rotational speed actually increases after commanding the actuator. This preliminary check allows the system to identify failure conditions before they lead to dangerous propeller underspeed states, enabling timely mitigation actions.
Solution Approach 2:
The system implements feedback by continuously monitoring the actual pitch angle and rotational speed values after actuator commands. The controller compares these actual values against expected changes, and when deviations indicate a failure condition, the system activates mitigation procedures including commanding a second actuator to hold the pitch angle and preventing further pitch angle increases.
2Reliability
If the pitch angle increases due to failure condition, then the propeller efficiency decreases, but increasing the pitch angle further may cause feathering which creates torque-related issues and affects flight safety
Solution Approach 1:
The controller applies preliminary anti-action by detecting the failure condition through monitoring pitch angle and rotational speed changes. Upon detection, the system immediately commands mitigation actions including using a second actuator to hold the pitch angle and preventing further pitch angle increases, thereby counteracting the harmful tendency toward feathering before it can severely impact flight safety.
Solution Approach 2:
The system provides beforehand cushioning by implementing a protective control strategy that prevents the pitch angle from increasing beyond safe limits during failure conditions. The controller monitors the situation and activates mitigation measures that cushion against the development of dangerous feathering states, protecting the aircraft from torque-related issues while maintaining acceptable propeller efficiency.
3Stability of the object's composition
If a second actuator is commanded to hold the pitch angle, then the propeller rotational speed can be stabilized, but the system complexity increases with additional actuators and control mechanisms
Solution Approach 1:
The control system implements universality by designing the second actuator to serve multiple functions: it can hold the pitch angle during failure conditions, and the same actuator infrastructure can potentially serve normal pitch angle control operations. This multi-functionality reduces the need for completely separate systems for normal and emergency operations, thereby limiting the increase in overall system complexity.
Solution Approach 2:
The controller acts as an intermediary that manages the complexity of having multiple actuators. It coordinates the first actuator for normal pitch angle adjustment and the second actuator for pitch angle holding during failures, providing a unified control interface that abstracts the underlying complexity from the pilot and simplifies the operational interface while maintaining the benefits of the multi-actuator system.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively stabilizes propeller rotational speed and pitch angle, reducing the risk of feathering and torque-related issues, thereby enhancing flight safety and operational efficiency.
Implementation Method 1
commanding a flow regulator located between a fluid source and a pitch angle actuator operatively connected to the blades to a first configuration to direct fluid from the fluid source to the pitch angle actuator to decrease the pitch angle of the blades
Implementation Method 2
commanding the flow regulator to a second configuration to block fluid from flowing between the fluid source and the pitch angle actuator
Data Source
AI summary
There is provided a method and a system for detecting and mitigating a propeller failure condition. An actual value of a rotational speed of the propeller and/or of a pitch angle of blades of the propeller is obtained. In response to determining that the speed is below a reference rotational speed for the propeller and/or determining that the pitch angle is above a pitch angle threshold, an actuator operatively connected to the blades is commanded to decrease the pitch angle to increase the speed towards the reference speed. After commanding of the actuator to decrease the pitch angle, a subsequent value of the speed and/or a subsequent value of the pitch angle is obtained. The actuator is commanded to hold the pitch angle in response to determining that the speed has failed to increase towards the reference speed and/or determining that the pitch angle has failed to decrease.