Perforated Plate for Aerial Refueling Boom Lateral Force Reduction
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Solution Overview
Problem
Aerial refueling booms experience significant lateral forces at sideslip due to low thickness - low drag airfoils, which reduce the operational envelope and are exacerbated by boom flexibility, and existing solutions like circular cross-sections or thick airfoils introduce drag and control complexities.
Innovation Solution
A passive device with perforated plates at the leading edge or along the chord of the boom, featuring irregular edges, reduces lateral forces by generating a low dynamic pressure wake and modulating its effect through length, width, and porosity adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If low thickness - low drag airfoils are used in the boom cross-section, then drag is reduced and operational envelope is expanded, but lateral force (lift) at sideslip increases significantly which opposes ruddervator control forces
Solution Approach 1:
The patent applies a porous leading edge device with multiple perforations that allows controlled flow through the structure. This porous configuration modifies the pressure distribution on the airfoil surface, reducing the lateral force generation mechanism while preserving the low drag characteristics of thin airfoils during normal operation.
Solution Approach 2:
The leading edge device acts as an intermediary element between the external flow and the airfoil surface. It mediates the flow field by creating a low dynamic pressure wake region that reduces the adverse pressure gradient and diminishes the lateral force generation without directly modifying the airfoil geometry.
2Force
If thick airfoils (70% thickness ratio) are used to generate negative lift at sideslip, then lateral force opposes ruddervator control force constructively, but drag increases and control complexity increases due to non-linearities
Solution Approach 1:
Instead of changing the fundamental airfoil thickness parameter, the invention modifies the flow field parameters through the leading edge device. By controlling the porosity, plate dimensions, and perforation patterns, it achieves the desired lateral force reduction while maintaining the original airfoil's favorable drag characteristics and linear control response.
3Force
If circular or quasi-circular boom cross-sections are used, then lateral force is reduced, but drag increases significantly
Solution Approach 1:
The invention applies a localized modification only at the leading edge region rather than changing the entire cross-section geometry. This local quality change allows the boom to maintain its aerodynamic (low drag) cross-section while introducing a specific flow control mechanism at the critical leading edge where flow separation and pressure distribution are established.
4Stability of the object's composition
If irregular edges are added to the plate to reduce flow induced oscillations, then stability is improved, but manufacturing complexity increases
Solution Approach 1:
The irregular edges are designed with specific curved geometries that promote flow mixing and reduce coherent vortex formation. The curved or rounded irregular patterns are more favorable for manufacturing using standard aerospace fabrication techniques compared to sharp or complex angular geometries, while still achieving the desired flow stabilization effect.
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
Significantly reduces lateral forces at sideslip while maintaining low drag, stabilizing the boom and expanding the operational envelope with reduced sensitivity to flight conditions and control complexities.
Implementation Method 1
A passive device with perforated plates at the leading edge or along the chord of the boom, featuring irregular edges, reduces lateral forces by generating a low dynamic pressure wake
Implementation Method 2
GB1019061 which discloses an aircraft wing that has a squared-off trailing edge TE with extensions having apertures which may be holes, or open or closed slots, the extensions may be parallel or divergent or convergent. The boundary layer bleeds through the apertures
Implementation Method 3
The plate of the device according to the invention comprises several perforations and has irregular edges to limit its negative effect on drag
Data Source
Figure 1~2c
Figure 3
Figure 4~5b
AI summary
Device to reduce the lateral force generated by an aerial refueling boom (11) of an aircraft characterized in that it comprises at least one plate (31), said plate (31) comprising two cantilevered wings (32, 33), said wings (32, 33) comprising perforations (34), so that the wake produced in the boom (11) has a lower dynamic pressure than that of the free stream.