Aircraft Stall Protection With Time-Varying AoA Limits in Icing
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Solution Overview
Problem
Current aircraft stall warning and protection systems in icing conditions often require increasing landing speeds and using longer runways due to inflexible maximum angle of attack settings, which are not dynamically adjusted based on the progression of ice accretion and de-icing, leading to inefficient landing operations.
Innovation Solution
The system continuously modifies the maximum angle of attack setting based on the time elapsed since ice detection and de-icing system activation, maintaining a consistent angle-of-attack margin to the stall angle, allowing for adaptive adjustments as ice is removed and re-accreted, thereby improving lift production and reducing the need for increased airspeed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the maximum angle of attack setting is reduced to prevent stall in icing conditions, then aircraft safety is improved, but landing performance deteriorates due to increased landing speeds and longer runway requirements
Solution Approach 1:
The patent applies dynamics by transitioning from a static maximum angle of attack setting to a dynamic, time-varying setting. The system continuously adjusts the maximum angle of attack based on elapsed time since ice detection, allowing the angle of attack limit to increase as the de-icing system becomes operational and ice accretion stabilizes. This dynamic adjustment optimizes both stall prevention and landing performance throughout the icing event timeline.
Solution Approach 2:
The patent implements parameter changes by modifying the maximum angle of attack parameter over time. The system changes this critical parameter from a fixed conservative value to a time-dependent value that increases as the de-icing system activates and becomes effective. This parameter evolution allows the aircraft to operate closer to the critical angle of attack once ice removal is underway, improving landing performance while maintaining safety margins.
2Reliability
If a conservative maximum angle of attack setting is used to account for worst-case ice accretion, then stall protection is improved, but operational efficiency deteriorates due to increased landing speeds
Solution Approach 1:
The patent applies preliminary action by activating the de-icing system immediately upon ice detection, before worst-case ice accretion fully develops. The system begins removing ice proactively, which allows the maximum angle of attack setting to be increased earlier than traditional conservative approaches. This preliminary de-icing action enables faster landing speeds while maintaining stall protection throughout the process.
3Productivity
If the maximum angle of attack setting is increased to improve landing performance, then operational efficiency is improved, but stall risk increases in severe icing conditions
Solution Approach 1:
The patent implements feedback by continuously monitoring ice detection system status and elapsed time, then using this information to adjust the maximum angle of attack setting. The system receives feedback from the de-icing system's operational status and modifies the angle of attack limit accordingly, increasing it only when the de-icing system is actively removing ice and the aircraft is no longer in a severe icing accretion phase. This feedback mechanism maintains stall resistance while enabling improved landing performance.
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
This approach enhances landing performance by maintaining a consistent angle-of-attack margin, allowing the aircraft to operate closer to the critical angle of attack, thus requiring shorter runways and reducing operational landing speeds during icing conditions.
Implementation Method 1
a de-icing system to remove ice accretions from the aircraft leading edges
Data Source
Figure 1A
Figure 1B
Figure 1C~1D
AI summary
This non-limiting technology proposes to modify the maximum angle of attack setting (αsetting) of the Stall Protection or Stall Warning Systems continuously or continually, according to the elapsed time since icing is first detected and/or the deicing system was activated.