Proprotor Lockout Assembly for Aeroelastic Stability in Forward Flight
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Solution Overview
Problem
Conventional tiltrotor aircraft are limited by forward airspeed-induced proprotor aeroelastic instability, which restricts their maximum airspeed in forward flight.
Innovation Solution
A proprotor lockout system that includes a drive shaft coupled to the rotor assembly, a nonrotating airframe structure, and a lock assembly with bearing assemblies and asymmetric slots, allowing for rotational locking and precise clocking of proprotor blades for blade folding during non-rotary flight modes, preventing rotation and aligning blades with blade grips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If proprotors are allowed to rotate freely during forward flight, then the aircraft can maintain flexibility for mode transition, but forward airspeed induces proprotor aeroelastic instability that limits maximum airspeed
Solution Approach 1:
The system dynamically transitions the proprotor assembly between rotating and non-rotating states based on flight mode requirements. During forward flight, the lockout mechanism engages to prevent rotation and eliminate aeroelastic instability. During VTOL or transition phases, the lockout disengages to allow free rotation for vertical thrust generation. This dynamic state change resolves the contradiction between speed and stability.
Solution Approach 2:
The invention extracts the rotational freedom from the proprotor assembly during forward flight by engaging the lockout mechanism. This separates the rotational function (needed for VTOL) from the forward flight condition, allowing the proprotor to remain stationary relative to the aircraft while the aircraft moves forward at high speed without aeroelastic instability.
2Shape
If proprotor blades are locked in place during non-rotary flight mode, then blade folding can be achieved for reduced drag, but the mechanism requires precise rotational alignment
Solution Approach 1:
The lock member features asymmetric slots that are precisely positioned to engage with bearing assemblies only at specific rotational orientations of the proprotor assembly. This asymmetric geometry ensures that the proprotor blades are automatically clocked to the correct position for folding, eliminating the need for separate alignment mechanisms and reducing manufacturing complexity while maintaining precision.
Solution Approach 2:
The lockout mechanism performs preliminary rotational alignment of the proprotor blades before engaging the locked position for folding. The asymmetric slots guide the bearing assemblies into engagement only when the blades are properly oriented, pre-aligning the components in the correct configuration before the final locked state is achieved.
3Stability of the object's composition
If a lockout mechanism is implemented to prevent proprotor rotation, then forward airspeed stability is improved, but the device complexity increases
Solution Approach 1:
The lockout mechanism combines multiple functions into a single integrated assembly: the lock member with asymmetric slots, the bearing assemblies, and the clocking mechanism are merged into one compact unit that performs rotation prevention, positional alignment, and blade folding enablement simultaneously. This reduces overall system complexity compared to having separate mechanisms for each function.
Solution Approach 2:
The lock member serves multiple functions: it prevents proprotor rotation during forward flight, provides precise rotational clocking for blade alignment, and enables the blade folding mechanism. This multi-functionality reduces the need for additional components and simplifies the overall system architecture while maintaining proprotor stability.
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.