Slotted Wing Flap Geometry for VTOL Hover Download and Cruise Drag
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Solution Overview
Problem
Existing VTOL aircraft designs face limitations in achieving high lift coefficients and low drag during different flight regimes due to rotor-induced flow interactions, leading to increased download and complexity, which are not adequately addressed by current flap systems.
Innovation Solution
A slotted wing flap system with an intermediate body between the wing body and trailing flap, allowing for a gap to open during hover flight to minimize download and form a continuous aerodynamic contour during cruise, enhancing lift coefficients and reducing drag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a large section of the wing is deflected downward to reduce the projected area in the rotor downwash, then download is reduced, but the wetted area increases causing increased drag in cruise flight
Solution Approach 1:
The wing flap is segmented into multiple elements including a main wing body, an intermediate body, and a trailing flap. This segmentation allows different portions to be positioned independently - the intermediate body can be retracted to reduce wetted area for low drag, while the trailing flap can be deflected to reduce download, resolving the contradiction between these two requirements.
Solution Approach 2:
The flap system employs dynamic positioning where the intermediate body can be retracted into the wing body channel during cruise to minimize wetted area and drag, while during hover the trailing flap is deflected downward to reduce download. This dynamic reconfiguration allows the system to optimize for different flight regimes, resolving the contradiction between drag reduction and download reduction.
2Force
If the wing area is increased to achieve higher lift coefficients, then maximum wing loading is improved, but penalties are incurred in both cruise and hover flight regimes
Solution Approach 1:
The system uses dynamic flap deflection to achieve high lift coefficients during takeoff and landing without permanently increasing wing area. During cruise, the flaps are retracted to maintain low drag, while during hover and transition, the trailing flap can be deflected to increase lift coefficient as needed, avoiding the penalties of permanently larger wing area.
Solution Approach 2:
The system changes the effective aerodynamic parameters by deflecting the trailing flap to different angles depending on flight regime. This allows the lift coefficient to be increased on demand without changing the physical wing area, resolving the contradiction between achieving high lift coefficients and avoiding drag penalties from increased wing area.
3Object-affected harmful factors
If a single flap element is used with slot closure at maximum deflection, then download is reduced in hover, but the complexity of forcing all rotor downwash flow around one side increases
Solution Approach 1:
The flap system is segmented into a main wing body, intermediate body, and trailing flap that can move independently. This segmentation allows the trailing flap to be deflected for download reduction while the intermediate body remains streamlined, reducing the complexity of flow management compared to forcing all flow around a single deflected element.
Solution Approach 2:
The intermediate body acts as an intermediary element between the main wing body and the trailing flap. It provides a streamlined transition that guides flow smoothly around the deflected trailing flap, reducing the complexity of flow management and the adverse effects of having a deflected flap in the downwash.
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 slotted wing flap system achieves increased lift coefficients and reduced drag across flight regimes, improving the performance and efficiency of VTOL aircraft by minimizing download and maintaining a smooth aerodynamic contour.
Implementation Method 1
By having an additional slot the boundary layer flow which grows on each element can be turned more aggressively than some other designs. This allows larger flap deflections and thereby enables higher lift coefficients.
Implementation Method 2
Flaps designed for low drag minimize the exposed wetted area and reduce sharp features which produce areas of flow separation.
Implementation Method 3
The gap is dimensioned and/or sized to provide a break in the aerodynamic contour represented by the wing body and the trailing flap when the aircraft wing is in a hover position.
Implementation Method 4
Flaps designed for low drag minimize the exposed wetted area and reduce sharp features which produce areas of flow separation.
Data Source
AI summary
Devices and systems of the inventive concept provide an aircraft flap system is deflected to achieve minimum drag in cruise, maximum coefficient of lift (CL) at low speed, and minimum download in hover. It does so by opening a gap or slot between an aircraft's wing body and an associated trailing flap during hover flight, while providing a continuous aerodynamic contour under other conditions.