Flight Control Surface Oscillation to Prevent Flow Separation

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Solution Overview

Problem

Aircraft flight control surfaces experience reduced effectiveness near the boundaries and extremes of their deflection range due to local airflow separation, leading to limited maneuverability and potential stall, which can result in loss of control and performance degradation.

Innovation Solution

Implementing a control system that generates forced oscillation signals when the flight control surface position exceeds a threshold, causing the actuator to oscillate the surface, thereby increasing dynamic lift and enhancing aerodynamic effectiveness beyond conventional static limits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the flight control surface is deflected to extreme positions to increase maneuverability, then the control authority is improved, but local airflow separation occurs causing effectiveness to decrease

Engineering Contradiction:

ImprovemaneuverabilityVSAvoidflight control surface effectiveness

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent applies forced oscillation to dynamically vary the flight control surface position around a commanded deflection angle. This dynamic approach allows the surface to operate in a regime where effective flow attachment is maintained while still achieving the desired control authority, resolving the contradiction between extreme deflection for maneuverability and flow separation reducing effectiveness

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system implements periodic oscillation of the flight control surface at a frequency and amplitude that prevents flow separation. By applying periodic motion, the control surface maintains aerodynamic effectiveness while achieving the necessary maneuverability, addressing the contradiction between extreme positions and flow separation

Inventive Principle:

Principle #19Periodic action

2Force

If the flight control surface operates near the boundaries of deflection range to maximize control authority, then maneuverability is improved, but aerodynamic effectiveness decreases due to flow separation

Engineering Contradiction:

Improvecontrol authorityVSAvoidaerodynamic effectiveness

Core Design Contradiction:

ForceVSReliability

Solution Approach 1:

The forced oscillation system dynamically adjusts the flight control surface position around the commanded deflection, preventing the surface from operating in the flow separation regime while maintaining control authority. This dynamic operation resolves the contradiction between maximizing control force and maintaining aerodynamic effectiveness

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the operational parameters by introducing oscillatory motion with specific frequency and amplitude. This parameter change allows the flight control surface to achieve high control authority while maintaining flow attachment and aerodynamic effectiveness, resolving the contradiction between force and reliability

Inventive Principle:

Principle #35Parameter changes

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 increases aircraft maneuverability, prevents loss of control, improves flight path departure prevention, and quickens recovery from unusual conditions by enhancing flight control surface effectiveness by up to 50% beyond conventional static lift maximums.

Implementation Method 1

Forced oscillation of the flight control surface advantageously generates dynamic lift as the limits of conventional static lift of the flight control surface are reached

Methodology Applied

Scientific EffectDynamic lift:

Implementation Method 2

Reduction of flight control surface effectiveness is caused by local airflow separation that occurs as the angle of the flight control surface relative to the direction of the local airflow increases

Methodology Applied

Scientific EffectAirflow separation: Flow Separation

Data Source

PatentUS11235859B2Methods and apparatus for enhancing aircraft flight control surface effectiveness via forced oscillation

Publication Date: 2022.02.01 THE BOEING CO

AI summary

Methods and apparatus for enhancing aircraft flight control surface effectiveness via forced oscillation are described. An example control system of an aircraft includes a flight control surface, an actuator, and one or more processors. The actuator is configured to move the flight control surface. The one or more processors are configured to determine a current position of the flight control surface. The one or more processors are further configured to determine whether the current position exceeds a position threshold. The one or more processors are further configured to generate a forced oscillation signal in response to determining that the current position exceeds the position threshold. The one or more processors are further configured to command the actuator to move the flight control surface based on the forced oscillation signal.