Aircraft Stabiliser Strake Vortex Flow Control
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Solution Overview
Problem
Aircraft horizontal stabilisers create aerodynamic drag while maintaining performance, and reducing their size without degrading stability and handling is challenging due to conflicting linear and non-linear aerodynamic characteristics.
Innovation Solution
Incorporating a strake with a sweep angle greater than 45° at the junction with the leading edge, which creates vortices to prevent flow separation and enhance lift at high angles of attack, allowing for a reduced stabiliser size without compromising stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the surface area of the horizontal stabiliser is reduced to decrease drag, then drag is reduced, but the aircraft's flying qualities (stability and handling) are degraded
Solution Approach 1:
The horizontal stabiliser is divided into two functional segments: a strake portion at the leading edge and a main stabiliser portion. The strake generates vortices that enhance lift on the main stabiliser, allowing the main stabiliser area to be reduced while maintaining stability. This segmentation enables independent optimization of drag reduction and stability maintenance.
Solution Approach 2:
The strake acts as an intermediary aerodynamic element that generates vortices to influence the flow over the main stabiliser. This vortex generation mechanism mediates between the conflicting requirements of reduced stabiliser area and maintained stability, allowing the smaller stabiliser to produce sufficient lift through enhanced flow characteristics.
2Productivity
If the horizontal stabiliser is made smaller to improve performance, then drag decreases, but the lift generation capability at high angles of attack is reduced
Solution Approach 1:
The strake generates periodic vortex structures that create dynamic pressure distributions over the main stabiliser. These vortices enhance the lift generation mechanism at high angles of attack, compensating for the reduced stabiliser area and maintaining adequate lift force throughout the flight envelope.
Solution Approach 2:
The invention changes the aerodynamic parameters of the stabiliser system by adding the strake element with specific geometric parameters (sweep angle greater than 45 degrees). This parameter change fundamentally alters the flow characteristics and lift generation mechanism, enabling reduced area while maintaining lift capability.
3Reliability
If the linear efficiency of the horizontal stabiliser is increased to improve balance criteria, then the gradient at fixed angle of attack increases, but the angles of attack for stalling are degraded
Solution Approach 1:
The strake provides localized aerodynamic enhancement at the leading edge region, creating vortices that specifically affect the pressure distribution over the main stabiliser. This local quality change improves the overall lift gradient for balance criteria while the vortex mechanism simultaneously delays stall by maintaining attached flow at higher angles of attack.
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 solution reduces drag, delays stalling, increases lift coefficients, and decreases structural loads and weight by maintaining linear characteristics while improving non-linear performance, enabling a smaller horizontal stabiliser design.
Implementation Method 1
the said strake has, at the junction of the said leading edge with the leading edge of the horizontal stabiliser, a sweep angle greater than 45°
Implementation Method 2
creates vortices to prevent flow separation and enhance lift at high angles of attack
Data Source
AI summary
An adjustable, or all-moving, horizontal stabiliser for an aircraft, the stabiliser having a leading edge, a trailing edge, a root and a tip, and a strake fixed with respect to the stabiliser and attached to, or integrally formed with, the stabiliser leading edge adjacent the root.