Movable Leading Edge for Aircraft Vertical Tail Flow Separation
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Solution Overview
Problem
Conventional aircraft vertical tails face challenges in maintaining control at high sideslip angles due to flow separation, leading to increased weight and drag when solutions like larger size or rudder enhancements are implemented, which are inefficient and costly.
Innovation Solution
A movable leading edge component for the vertical tail that can be extended to create a gap and pivot, reducing pressure peaks and delaying flow separation, thereby increasing the maximum yawing moment without adding weight or drag, and can be retracted for high-speed flight to minimize drag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the vertical tail size is increased to maintain control at high sideslip angles, then flow separation is delayed and control is improved, but weight and drag increase
Solution Approach 1:
The patent applies a movable leading edge device that can dynamically change position based on flight conditions. The device extends into the airflow at high sideslip angles to delay flow separation and retracts at low sideslip angles to minimize drag and weight effects, making the tail structure adaptive rather than statically oversized
Solution Approach 2:
The leading edge device extends in advance before flow separation would occur at high sideslip angles, modifying the airflow pattern proactively. This preliminary action prevents the harmful flow separation phenomenon before it can develop, maintaining control effectiveness without requiring a permanently larger tail
2Reliability
If the rudder size is increased to maintain control at high sideslip angles, then control authority is improved, but weight and drag increase
Solution Approach 1:
The movable leading edge device provides dynamic control augmentation that allows the existing rudder to operate effectively at high sideslip angles without requiring a larger rudder structure. The device adapts its position based on the sideslip angle, providing control authority only when needed
3Reliability
If the vertical tail size is increased to maintain control at high sideslip angles, then flow separation is delayed, but skin friction drag increases during cruise
Solution Approach 1:
The leading edge device is movable and retracts to a streamlined position during high-speed cruise flight, minimizing its impact on skin friction drag. When extended at high sideslip angles, it delays flow separation; when retracted, it maintains a sleek profile that does not significantly increase drag, thus resolving the contradiction between flow attachment and drag reduction
Solution Approach 2:
The leading edge device operates periodically based on flight conditions - extending when high sideslip angles are encountered and retracting during normal cruise. This periodic deployment ensures flow separation is delayed only when necessary, while minimizing energy loss during phases where the device is not needed
4Reliability
If an asymmetric leading edge device is used on the vertical tail, then flow separation is delayed at positive angles of attack, but the device is not suitable for sideslip angle operation
Solution Approach 1:
The patent uses a symmetric leading edge device design that can effectively handle both positive and negative sideslip angles. Unlike asymmetric wing devices optimized for one direction, this symmetric configuration provides equal effectiveness in both directions of sideslip, making it versatile for vertical tail application where airflow can come from either side
Solution Approach 2:
The leading edge device is designed to perform multiple functions: it delays flow separation at both positive and negative sideslip angles, and can operate effectively across a range of flight conditions. This universal design makes it suitable for vertical tail application where the aircraft may experience sideslip in either direction, unlike wing-specific asymmetric devices
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 allows aircraft to operate at higher sideslip angles with increased yawing moment, reducing the need for larger tails and rudder sizes, thus minimizing weight and drag, and enabling operation at lower speeds without increasing landing distances or fuel consumption.
Implementation Method 1
delay flow separation from the tail of the mobile platform as the sideslip angle increases
Implementation Method 2
The moveable leading edge element serves to turn the flow of air before it reaches the main element, thus reducing the pressure peak on the main element
Implementation Method 3
The lower pressure peak serves to reduce deceleration of the boundary layer over the main element, thus making it more resistant to flow separation
Data Source
AI summary
A vertical tail for use with an aircraft or other form of mobile platform. The vertical tail includes a main element which is fixedly secured to the mobile platform, and a leading edge element that is movably secured to the main element. The cross section of the leading edge element is symmetric about the cruise chord line of the tail. The leading edge element can be pivoted and/or extended to create a gap with the main (fixed) element. The movable leading edge element is used to increase the maximum yawing moment provided by the vertical tail. The maximum yawing moment is increased when air flow is incident from either side of the vertical tail.