Elastomeric Pitch Lock Restraint for Tiltrotor Aeroelastic Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Tiltrotor aircraft face limitations in maximum airspeed during forward flight due to forward airspeed-induced proprotor aeroelastic instability, restricting their high-speed cruising capabilities.
Innovation Solution
The implementation of a pitch lock mechanism that enables and disables the pitching degree of freedom of rotor blade assemblies, combined with a gimbal lock and blade stop assembly, allows for transitions between rotary and non-rotary flight modes, effectively managing the proprotor blades' orientation to overcome aeroelastic instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If proprotors maintain pitching degree of freedom during forward flight, then rotor blade assembly can adapt to varying flight conditions, but forward airspeed-induced proprotor aeroelastic instability limits maximum airspeed
Solution Approach 1:
The pitch lock mechanism dynamically transitions between locked and unlocked states based on flight mode. During forward flight, the pitch lock engages to constrain the pitching degree of freedom, eliminating aeroelastic instability. During rotary flight modes, the pitch lock disengages to allow full pitching freedom for blade pitch control. This dynamic switching resolves the contradiction by adapting the system's degrees of freedom to the current operational requirements.
2Speed
If pitch lock mechanism is engaged to stabilize proprotor blades, then forward cruising speed increases, but mechanism complexity increases
Solution Approach 1:
The pitch lock mechanism is integrated with the existing blade stop assembly and cuff structure. The hasp engages with tabs that are part of the blade stop assembly, and rollers are mounted on the hasp to interact with ramp surfaces on the tabs. By merging the pitch lock function with existing structural elements, the patent achieves blade stabilization without proportionally increasing overall mechanism complexity.
Solution Approach 2:
The rollers act as intermediary elements between the hasp and the tabs with ramp surfaces. These rollers enable smooth engagement and disengagement of the pitch lock while distributing contact forces. The elastomeric material of the rollers provides cushioning and facilitates controlled locking/unlocking actions, simplifying the interaction between rigid components.
3Reliability
If rollers with elastomeric material are used in pitch lock, then cushioning and preload are achieved, but friction increases
Solution Approach 1:
The elastomeric material in the rollers provides beforehand cushioning by absorbing shock and vibration during the locking and unlocking processes. This cushioning effect protects the rigid tabs and hasp from impact forces, improving reliability. The elastomeric rollers also maintain continuous contact through their compliance, ensuring consistent preload on the locked tabs.
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
Enables tiltrotor aircraft to achieve higher forward cruising speeds by stabilizing the proprotor blades, allowing for seamless transitions between helicopter and airplane flight modes, thereby enhancing operational versatility.
Implementation Method 1
rollers rotatably coupled to the hasp on opposite sides of the central opening, where the rollers engage the first and second ramp surfaces and retain the first and the second tabs in the central opening
Data Source
AI summary
An exemplary pitch lock for a tiltrotor aircraft to enable and disable a pitching degree of freedom of a rotor blade assembly includes a first tab coupled to a blade stop assembly, the first tab having a first ramp surface, a second tab coupled to a blade cuff, the second tab having a second ramp surface, a hasp having a central opening to receive the first and the second tab and rollers rotatably coupled to the hasp on opposite sides of the central opening, where the rollers engage the first and second ramp surfaces and retain the first and the second tabs in the central opening.