Aircraft Winglet Flow Fence for Sideslip Stability
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Solution Overview
Problem
Aircraft winglets experience reduced lateral stability and undesirable rolling moment behavior at high sideslip angles due to airflow separation, especially under icing conditions or contamination, which can lead to certification issues and decreased performance.
Innovation Solution
A flow fence is positioned on the wing surface inboard from the winglet, spaced not exceeding 100% of the winglet root chord length, to delay or prevent airflow separation on the winglet inboard surface, thereby increasing lateral stability and linearizing aircraft behavior at high sideslip angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If devices are added to winglets to prevent separated airflow, then lateral stability is improved, but aerodynamic drag increases and aircraft performance degrades
Solution Approach 1:
The patent extracts and removes the flow separation problem by positioning the flow fence at a specific location (inboard from the winglet, spaced not exceeding 100% of the winglet root chord length) to prevent separation at its source rather than adding complex devices to the winglet itself. This eliminates the need for additional winglet modifications that would increase drag.
Solution Approach 2:
The flow fence acts as an intermediary element between the wing surface and the winglet. By placing it on the wing surface inboard from the winglet, it mediates the airflow before it reaches the winglet, preventing separation without directly modifying the winglet structure. This intermediary approach maintains clean winglet surfaces and minimizes drag.
2Object-affected harmful factors
If ice protection systems are implemented on winglet leading edge, then ice accumulation is prevented, but weight, cost, and system complexity increase
Solution Approach 1:
The patent converts the harmful effect of potential ice accumulation into a beneficial aerodynamic feature. By designing the flow fence to extend to a position overlapping with the winglet, it creates a protective geometry that prevents airflow separation even when ice is present, rather than actively preventing ice formation. This passive approach avoids complex heating or mechanical removal systems.
Solution Approach 2:
The patent changes the geometric parameters of the wing assembly by adding the flow fence with specific positioning (inboard spacing not exceeding 100% of winglet root chord length). This geometric modification alters the airflow parameters and pressure distribution, making the system resistant to ice-induced separation without requiring active ice protection systems.
3Reliability
If flow fence is positioned closer to winglet, then airflow separation is better prevented, but interference with winglet lift may increase
Solution Approach 1:
The patent applies partial action by positioning the flow fence at an optimized distance from the winglet (inboard spacing not exceeding 100% of the winglet root chord length). This partial positioning is sufficient to prevent airflow separation at the critical inboard surface while maintaining adequate clearance to avoid excessive interference with the winglet's lift-generating airflow.
Solution Approach 2:
The patent resolves the conflict by operating in another dimension - extending the flow fence spanwise to overlap with the winglet rather than positioning it purely in the chordwise direction. This dimensional approach allows the flow fence to control airflow separation on the inboard surface while the overlap geometry ensures smooth flow transition to the winglet, maintaining lift efficiency.
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 flow fence effectively reduces airflow separation, enhancing lateral stability and maintaining lift, even under icing or contamination, without adding complex systems, weight, or increasing cost, thus meeting certification requirements and improving aircraft controllability.
Implementation Method 1
airflow over the inboard side of the winglet may separate from the surface. This separation effect reduces winglet lift, reducing lateral stability
Data Source
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AI summary
A wing of an aircraft that includes a wing leading edge, a wing trailing edge, and a wing surface defined by a wing upper surface and a wing lower surface is described herein. The wing extends from the wing root to the wingtip, and the wingtip has a wingtip chord. A winglet extends from the wingtip and has a winglet leading edge, a winglet trailing edge, a winglet inboard surface, a winglet outboard surface, a winglet root having a winglet root chord, and a winglet tip. A flow fence is disposed on the wing surface inboard from the winglet and overlapping with the winglet. The flow fence is adapted to delay and/or prevent airflow separation on the winglet inboard surface at high angle of sideslip, increasing lateral stability and linearizing aircraft behavior at high angle of sideslip.