Variable Chord Helicopter Rotor Blade for Retreating Stall
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Solution Overview
Problem
Retreating blade stall limits the operating envelope of rotorcraft, particularly at high altitudes, airspeeds, or gross weights, leading to loss of lift, increased drag, and high vibration and control loads.
Innovation Solution
A variable chord rotor blade design featuring an extensible chord plate that can be extended or retracted within the rotor blade, adjusting the chord line based on flight conditions to prevent stall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed chord rotor blade is used, then the structure is simple and manufacturing is easy, but retreating blade stall occurs at high altitudes, airspeeds, or gross weights limiting the operating envelope
Solution Approach 1:
The rotor blade incorporates a morphing airfoil section with variable chord length that can dynamically adjust during rotation. The leading edge flap is hinged to allow angular adjustment, transforming the static blade into a dynamic system that adapts its geometry to prevent retreating blade stall while maintaining simplicity.
Solution Approach 2:
The invention changes the geometric parameter of the rotor blade by allowing the leading edge flap to rotate and adjust the chord length. This parameter change enables the blade to adapt to different flight conditions (high altitude, high airspeed, high gross weight) and prevents stall without requiring a completely complex redesign.
2Reliability
If trailing edge flaps or Gurney flaps are used to control stall, then retreating blade stall is alleviated to some extent, but the chord line dimension remains fixed and non-adjustable
Solution Approach 1:
Instead of using fixed trailing edge flaps or Gurney flaps, the invention implements a dynamic leading edge flap that can rotate to different angles. This dynamic adjustment allows the chord length to be modified in real-time based on flight conditions, providing both stall control and adaptability that fixed configurations cannot achieve.
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 solution enhances maneuverability, reduces noise, and allows operation at higher altitudes and speeds by alleviating stall conditions, while maintaining efficiency within the flight envelope.
Implementation Method 1
A rotor blade when moving in the same direction as the aircraft is called an advancing blade and when moving in the opposite direction is called a retreating blade. One of the primary factors limiting an operating envelope of a rotorcraft is onset of retreating blade stall.
Implementation Method 2
Retreating blade stall is a hazardous flight condition in helicopters and other rotary wing aircraft, where the rotor blade rotating away from the direction of flight stalls. Retreating blade stall leads to a loss in lift, sharp increase in drag and pitching moment
Data Source
AI summary
A variable chord morphing helicopter rotor blade is disclosed. The variable chord morphing helicopter rotor blade includes an extensible quasi-static chord section connected to the rotor blade, an adjusted airfoil chord length of the rotor blade corresponding to extension of the quasi-static chord section relative to a baseline airfoil chord length, the adjusted airfoil chord length determined according to helicopter flight conditions.