Rotorcraft Fairing with Undulating Trailing Edges
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Aircraft structural elements, particularly rotorcraft like helicopters, face significant aerodynamic drag issues due to their design, leading to increased energy dissipation, vibrations, and instability, especially with traditional ducted rear rotors like the Fenestron, which have a straight base causing aerodynamic separation and turbulence.
Innovation Solution
The introduction of a fairing with a disturbed shape featuring reliefs and hollows along the trailing edges, forming regular or irregular undulations that extend between the trailing edges, reduces aerodynamic drag by modifying the wake structure and promoting faster vortex dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a straight base is used to close the rear part of the Fenestron fairing, then the structure is simple and easy to manufacture, but aerodynamic drag increases significantly due to flow separation and turbulence
Solution Approach 1:
The patent applies curvature by replacing the straight base with an arc-shaped base that follows a curved trajectory. This curved geometry allows the air flow to remain attached to the surface longer, reducing flow separation and turbulence. The arc-shaped base creates a gradual transition rather than an abrupt termination, thereby reducing aerodynamic drag while maintaining structural feasibility.
2Loss of energy
If the fairing thickness is reduced to less than 15% relative thickness, then aerodynamic drag decreases with profiled shape, but the device mass increases significantly and centering problems occur
Solution Approach 1:
The patent applies local quality by modifying only the base region of the fairing with an arc-shaped geometry while keeping the rest of the fairing structure relatively unchanged. This localized modification targets the specific area where flow separation occurs, reducing aerodynamic drag without requiring a complete redesign of the entire fairing structure, thereby minimizing additional mass.
3Loss of energy
If a profiled part is added to reduce drag, then aerodynamic performance improves in forward flight, but flight quality deteriorates due to route instability and yaw oscillations
Solution Approach 1:
The arc-shaped base with its curved geometry creates a more gradual flow transition that reduces the intensity and variability of wake fluctuations. This curvature helps stabilize the flow separation pattern, reducing the beating of the wake and the resulting self-sustaining oscillations in yaw, thereby improving flight stability while maintaining drag reduction benefits.
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 design reduces aerodynamic drag, minimizes fuel consumption, maintains aircraft stability, and avoids excess weight, providing a passive solution applicable to various rotor types without altering flight qualities.
Implementation Method 1
aerodynamic drag in forward flight
Implementation Method 2
aerodynamic separation, that is to say a zone of concentration of vortices and relatively extensive turbulence
Implementation Method 3
relatively extensive turbulence
Data Source
Figure 1~3
AI summary
The present invention relates to a fairing (1) for a structural element of an aircraft, comprising a rear portion (2) substantially orthogonal to the longitudinal direction (L) of the aircraft, extending between two spaced trailing edges (3, 4) and thus having a determined width, said rear portion (2) at least partially obstructing the internal volume delimited by the fairing (1) and generating aerodynamic drag in forward flight. According to the invention, the rear portion has, at least at the trailing edges (3, 4), a perturbed shape along the paths of the airflow (5).