Multirotor Autorotation via Collective Pitch Control
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Solution Overview
Problem
Multirotor aircraft with fixed-pitch rotor blades lack maneuverability and are unable to autorotate in case of engine failure due to their rotational inertia and fixed blade angles, limiting their safety and control during emergency situations.
Innovation Solution
The implementation of a collective pitch control system that allows for adjustable pitch angles of rotor blades, enabling differential control of thrust and lift, and the use of freewheeling assemblies to maintain rotor speed during autorotation, simplifying the swashplate design and reducing the complexity and weight of propulsion systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed-pitch rotor blades are used in multirotor aircraft, then the propulsion system complexity is reduced, but the aircraft loses autorotation capability and maneuverability
Solution Approach 1:
The patent implements variable-pitch rotor blades that can dynamically adjust their pitch angle through collective pitch control systems. This allows the blades to transition between fixed-pitch and variable-pitch configurations, enabling autorotation capability while maintaining simplified propulsion system architecture during normal operation
Solution Approach 2:
The patent changes the pitch parameter of rotor blades from fixed to variable, allowing dynamic adjustment of blade angle of attack. This parameter change enables the aircraft to achieve autorotation by adjusting pitch angles during engine failure, while maintaining relatively simple propulsion system design through controlled parameter variation
2Reliability
If collective pitch control systems are implemented, then autorotation capability is achieved, but the device complexity and weight increase
Solution Approach 1:
The patent designs a collective pitch control system that serves multiple functions: enabling autorotation during engine failure, improving maneuverability during normal flight, and maintaining simplified control architecture. This multi-functionality justifies the added complexity by providing multiple benefits from a single system
Solution Approach 2:
The patent merges the collective pitch control mechanism with the existing propulsion system architecture, integrating pitch adjustment capabilities into the rotor blade assembly rather than adding completely separate control systems. This integration reduces overall system complexity while maintaining autorotation capability
3Device complexity
If fixed-pitch rotor blades are used, then the aircraft structure is simplified, but maneuverability and safety during emergency are limited
Solution Approach 1:
The patent transitions from static fixed-pitch rotor blades to dynamic variable-pitch rotor blades that can adjust their angle of attack in real-time. This dynamic capability enables precise maneuvering control while maintaining relatively simple rotor blade structure through controlled pitch variation rather than complex mechanical designs
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
This solution enhances the aircraft's maneuverability, allows for safe autorotation in case of engine failure, and reduces the complexity and weight of the propulsion systems, providing a safer and more controlled descent and landing.
Implementation Method 1
a freewheeling assembly configured to disengage the unpowered proprotor from the engine and maintain a rotational speed of the unpowered proprotor
Data Source
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AI summary
A multirotor aircraft (101) comprises at least three proprotors (114-117). Each proprotor has a plurality of rotor blades (118-121) pivotably attached to a mast assembly. When a rotor blade pitch angle is changed for a proprotor, all rotor blades on the proprotor change to a same pitch angle. The proprotors are configured to spin freely when a power source is disengaged or fails. In various embodiments, one or more engines provides power to each proprotor, or at least one engine provides power to two or more proprotors. A rotor blade control system (300) is configured to control a collective rotor blade pitch angle on each proprotor independently of the rotor blade pitch on the other proprotors. The rotor blade control system is configured to set a negative collective rotor blade pitch angle on an unpowered proprotor, such as in response to manual inputs by a pilot or in response to current engine conditions.