Tiltrotor Mast Lockout System for Aeroelastic Stability
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Solution Overview
Problem
Tiltrotor aircraft face limitations in maximum airspeed due to forward airspeed-induced proprotor aeroelastic instability, which restricts their performance in forward flight.
Innovation Solution
A mast lockout system that includes a rotatable mast coupled to the proprotor assembly, a proprotor gearbox, and a lock assembly with lock members to prevent rotation of the mast, allowing for the alignment and folding of proprotor blades during non-rotary flight modes, thereby overcoming aeroelastic instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the proprotor assembly is allowed to rotate freely, then the aircraft can operate in rotary flight mode for vertical takeoff and landing, but the mast rotation causes aeroelastic instability that limits maximum forward airspeed
Solution Approach 1:
The system dynamically changes the rotational state of the proprotor assembly based on flight mode. In rotary flight mode, the proprotor is free to rotate to generate vertical thrust. In forward flight mode, the lockout system engages to prevent rotation, eliminating aeroelastic instability and enabling higher forward airspeeds. This dynamic transition between rotating and locked states resolves the contradiction between maintaining rotary capability and preventing speed-limiting instability.
2Stability of the object's composition
If the mast is locked to prevent rotation, then forward airspeed stability is improved, but the ability to transition between rotary and non-rotary flight modes is restricted
Solution Approach 1:
The lockout system is designed to be dynamically controllable, transitioning between locked and unlocked states based on flight mode requirements. The system includes actuation mechanisms that allow the mast to be locked during forward flight for stability while remaining unlockable to restore rotary capability when needed. This dynamic controllability resolves the contradiction by making the stability enhancement reversible and adaptive to operational needs.
Solution Approach 2:
The lockout system acts as an intermediary mechanism between the proprotor assembly and the aircraft airframe. It provides a controlled connection that can either allow rotation for vertical flight or prevent rotation for forward flight. This intermediary function enables the system to mediate between the conflicting requirements of rotary versatility and forward flight stability, allowing smooth transitions between flight modes.
3Stability of the object's composition
If a lockout system is added to prevent mast rotation, then aeroelastic instability is reduced, but the device complexity increases
Solution Approach 1:
The lockout function is extracted as a separate, dedicated system rather than being integrated into the existing proprotor drive mechanism. This separation allows the lockout system to be designed independently with its own actuators, sensors, and control logic, simplifying the overall architecture. By taking out the locking function as a distinct module, the system achieves the stability benefit while managing complexity through functional separation.
Solution Approach 2:
The lockout system incorporates self-monitoring and self-actuation capabilities through integrated sensors and control mechanisms. The system can detect flight mode transitions and automatically engage or disengage the lockout mechanism without requiring complex external control systems. This self-service approach reduces overall system complexity by making the lockout system autonomously manageable while maintaining proprotor stability.
Data Source
AI summary
A mast lockout system for a tiltrotor aircraft having a proprotor assembly. The system includes a mast coupled to and rotatable with the proprotor assembly. A proprotor gearbox having a proprotor gearbox housing is configured to transmit torque and rotation energy to the mast. A lock assembly has first and second lock members. The first lock member is coupled to the mast between first and second mast bearings and configured to rotate with the mast. The second lock member is coupled to the proprotor gearbox housing. The lock assembly has a first position in which the first and second lock members are disengaged, thereby allowing rotation of the mast. The lock assembly has a second position in which the first and second lock members are engaged, thereby preventing rotation of the mast. The lock assembly is actuatable between the first and second positions.