Proprotor Lockout Assembly for High-Speed Tiltrotor Flight
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Solution Overview
Problem
Conventional tiltrotor aircraft are limited by forward airspeed due to proprotor aeroelastic instability, which affects their maximum airspeed in forward flight.
Innovation Solution
A lockout system for tiltrotor aircraft that includes a drive shaft coupled to a rotor assembly with a nonrotating airframe structure and a lock assembly having first and second lock members with asymmetric slots to prevent rotation of the proprotor assemblies during non-rotary flight modes, allowing for precise alignment of proprotor blades for blade folding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If proprotors are allowed to rotate during non-rotary flight mode, then the aircraft can maintain flexibility for mode transition, but proprotor aeroelastic instability occurs limiting maximum airspeed
Solution Approach 1:
The lockout system dynamically transitions between locked and unlocked states based on flight mode. During non-rotary flight, the lock assembly engages to prevent proprotor rotation and eliminate aeroelastic instability. During rotary flight or mode transitions, the lock disengages to allow free rotation. This dynamic state change resolves the contradiction by making the system rigid when stability is needed and flexible when maneuverability is needed.
Solution Approach 2:
The system changes the rotational parameter of the proprotor from free rotation to constrained rotation based on flight conditions. The lock assembly modifies the boundary conditions of the proprotor, transitioning it from an unconstrained rotating system (prone to aeroelastic instability) to a constrained system (stable at high speeds).
2Speed
If proprotors are locked to prevent rotation, then forward airspeed capability increases, but precise alignment of proprotor blades for folding becomes more difficult
Solution Approach 1:
The lockout system incorporates a clocking mechanism that performs preliminary alignment of the proprotor blades to the correct angular position before the lock engages. This ensures that when the proprotor is locked in the non-rotary mode, the blades are already precisely positioned for folding operations, eliminating the need for complex alignment procedures after locking.
Solution Approach 2:
The lock assembly uses asymmetric slot geometry to provide both locking and clocking functions. The asymmetric shape of the slots in the lock member allows the proprotor to be locked in a specific angular orientation, automatically achieving precise blade alignment while maintaining the locked state for high-speed flight.
3Stability of the object's composition
If a lockout system is added to prevent proprotor rotation, then aeroelastic instability is eliminated, but device complexity increases
Solution Approach 1:
The lockout system combines multiple functions into a single integrated assembly: rotation locking, blade clocking, and mode transition indication. The lock assembly serves as both the locking mechanism and the clocking mechanism, eliminating the need for separate systems and reducing overall complexity despite adding necessary functionality.
Solution Approach 2:
The lock assembly is designed as a multi-functional component that performs locking, clocking, and provides mechanical indication of lock status. This universal design approach consolidates what could be multiple separate systems into one integrated unit, minimizing the increase in device complexity while achieving all necessary functions.
Data Source
AI summary
A lockout system for an aircraft having a rotor assembly. The lockout system includes a drive shaft coupled to and rotatable with the rotor assembly, a nonrotating airframe structure disposed proximate the drive shaft and a lock assembly having first and second lock members. The first lock member is rotatable with the drive shaft and includes a plurality of bearing assemblies. The second lock member is coupled to the nonrotating airframe structure and includes a cradle having a plurality of asymmetric slots each with a leading ramp and a trailing stop. The lock assembly has a disengaged position in which rotation of the drive shaft is allowed and an engaged position in which each of the bearing assemblies is seated within one of the asymmetric slots to prevent rotation of the drive shaft. The lock assembly is actuatable between the engaged and disengaged positions.