Variable Wing Area Stabilizer for Rotorcraft
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Solution Overview
Problem
Rotorcrafts, particularly helicopters, face challenges with the 'tail fin blocking' and 'attitude hump' phenomena during hovering and low-speed flights, where the tail rotor's air stream interacts with stabilizer devices, reducing efficiency and requiring increased power, and the air flow from the main rotor affects pitching stabilizer means, causing loss of lift and nose-up attitudes.
Innovation Solution
A rotorcraft with variable wing area stabilizer devices, featuring a stationary airfoil surface and a movable airfoil surface that translates between retracted and extended positions based on speed thresholds, controlled by a mover system and actuator, to minimize wing area at low speeds and maximize it at higher speeds, reducing the impact of air flow and tail rotor interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the tail fin carries the tail rotor, then yaw control is achieved, but the air stream from the tail rotor is blocked by the tail fin during hovering or low-speed flight, reducing efficiency
Solution Approach 1:
The tail fin is designed with variable geometry that allows it to change its configuration dynamically. During hovering or low-speed flight, the tail fin adjusts to a position that does not block the air stream from the tail rotor, thereby maintaining rotor efficiency. During forward flight, the tail fin assumes its conventional stabilizing position.
Solution Approach 2:
The invention changes the geometric parameters of the tail fin based on flight conditions. By adjusting the tail fin's angle, area, or position as a parameter, the system optimizes both yaw control effectiveness and tail rotor efficiency across different flight regimes.
2Use of energy by moving object
If the tail fin area is reduced to limit power increase, then power requirements decrease, but the tail fin becomes less effective in forward flight
Solution Approach 1:
The tail fin employs variable geometry that allows it to be small or retracted during hovering operations to reduce power requirements, and then extended or positioned optimally during forward flight to maximize stabilizing effectiveness. This dynamic adjustment resolves the contradiction between power consumption and stabilizer performance.
Solution Approach 2:
The tail fin area or position is periodically adjusted according to the flight phase. During hovering, the fin is minimized; during transition and forward flight, it is deployed to full effectiveness. This periodic adaptation allows the system to optimize power usage at each phase without compromising overall reliability.
3Reliability
If pitching stabilizer means have large wing area, then stabilizing effectiveness increases, but air flow from the main rotor impacts against the stabilizer means during hovering or low-speed flight, causing loss of lift and nose-up attitude
Solution Approach 1:
The pitching stabilizer means is designed with variable wing area that can be dynamically adjusted. During hovering or low-speed flight, the wing area is reduced or the stabilizer is positioned to avoid the main rotor downwash, eliminating the harmful air flow impact. During forward flight, the full wing area is deployed to maximize pitching stability.
Solution Approach 2:
The pitching stabilizer may be divided into multiple segments or surfaces that can be independently controlled. This allows selective deployment of different portions of the stabilizer based on flight conditions, enabling the system to avoid air flow impact when necessary while maintaining large effective area when beneficial.
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 variable wing area stabilizer devices minimize the tail fin blocking and attitude hump phenomena by adjusting the wing area in response to speed, enhancing rotorcraft performance and reducing power requirements during various flight stages.
Implementation Method 1
the air stream generated by the tail rotor can impact against the tail fin during the stages of hovering or low speed flight. The tail fin then blocks that air stream in part, thereby reducing the yaw moment exerted by the tail rotor on the airframe of the aircraft.
Implementation Method 2
such stabilizer devices include stabilizer means for stabilizing pitching movements of the aircraft. Means for stabilizing pitching movements conventionally comprise at least one stabilizer surface presenting an angle of absolute value lying in the range 0° and plus or minus 90° relative to the anteroposterior plane of symmetry of the aircraft.
Data Source
AI summary
A rotorcraft having at least one stabilizer device of the tail plane and/or of the tail fin type. At least one stabilizer device is a variable wing area stabilizer device comprising an airfoil member provided with a stationary airfoil surface and a movable airfoil surface. A control system is connected to a mover system for moving the movable airfoil surface in translation between a refracted position for occupying when the rotorcraft has a forward speed less than a first speed threshold, and an extended position for occupying when the rotorcraft has a forward air speed greater than a second speed threshold greater than the first speed threshold.