Fail-Operational Rotorcraft Mechanical Coupling
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Solution Overview
Problem
Current multiple lifting-rotor aircraft designs are unable to continue safe flight to a landing in the event of a rotor failure, as the mechanical linkage between rotors can cause lift imbalances and safety issues during forward flight, limiting their utility in transportation roles.
Innovation Solution
Implementing a system that allows for the disengagement and reengagement of rotor mechanical coupling during flight using devices like dog clutches, friction clutches, and collapsible clutches, enabling the aircraft to transition from VTOL to wing-borne flight and maintain safety in case of rotor failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical linkage between rotors is implemented to prevent lift imbalance in vertical flight, then hover safety is improved, but forward flight safety deteriorates due to secondary damage from severe vibration when one rotor fails
Solution Approach 1:
The patent applies a dynamic approach by using a centrifugal clutch that automatically engages or disengages based on rotational speed. At low speeds (hover), the clutch engages to link rotors and prevent lift imbalance. At high speeds (forward flight), the clutch disengages to isolate rotors and prevent severe vibration damage. This dynamic switching resolves the contradiction between hover safety and forward flight safety.
2Reliability
If cross shafts are permanently engaged between rotors to provide hover lift when an engine fails, then vertical flight reliability is improved, but the ability to continue forward flight with a disabled rotor is lost
Solution Approach 1:
The centrifugal clutch provides dynamic engagement/disengagement based on operational mode. In vertical flight, the clutch engages to link rotors for reliable hover operation. In forward flight with a disabled rotor, the clutch disengages to allow the aircraft to continue flying. This dynamic behavior enables both vertical flight reliability and forward flight adaptability.
Solution Approach 2:
The drive system is segmented into independently controllable rotor groups through the centrifugal clutch. This segmentation allows one rotor to be isolated from the other when needed, enabling the aircraft to continue forward flight with a disabled rotor while maintaining vertical flight reliability when the clutch is engaged.
3Ease of operation
If one-way clutches are used to automatically disengage non-operational engines, then engine failure response is improved, but rotor failure cannot be addressed as the mechanical linkage remains connected
Solution Approach 1:
The centrifugal clutch acts as an intermediary device between the engine and rotor, providing automatic disengagement based on rotational speed rather than engine operation status. This intermediary mechanism addresses rotor failure safety by automatically isolating a disabled rotor from the drive system, while still allowing automatic disengagement functionality for engine failures.
Data Source
AI summary
A rotorcraft having multiple rotors, and wings that provide lift in forward flight, has a mechanical coupling between rotors that can be disengaged and optionally reengaged, during flight. The coupling, which can prevent a failure of one rotor from interfering with rotation of the other rotor(s), can be accomplished using many different types of devices, including for example, dog clutches, friction clutches, and collapsible clutches. Disengagement can range from being completely under control of an operator, to partially under operator control, to completely automatic. Among many other benefits, designing, manufacturing, fitting, retrofitting or in some other manner providing an aircraft with a device that can disengage rotation of one of the rotors from that of another one of the rotors during flight can be used to improve survivability in an emergency situation.