Collective Stick Tactile Feedback for Rotor Overspeed Protection
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Solution Overview
Problem
As rotorcraft become larger and more complex, managing flight parameters and controls becomes increasingly challenging due to tightly coupled aerodynamic characteristics, making it difficult for pilots to maintain stable flight without overwhelming workload, especially in situations like rotor overspeed conditions where main rotor RPM can exceed safe limits.
Innovation Solution
A fly-by-wire (FBW) system with a flight control computer that provides tactile cues to the pilot through the collective stick, adjusting its position to increase collective angle and reduce RPM, offering a soft stop that can be overridden by the pilot, while continuously monitoring and maintaining main rotor speed within a target threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a rotorcraft uses larger and more complex rotor systems to generate sufficient lift and thrust, then the aerodynamic performance is improved, but the difficulty of managing flight parameters and maintaining stable flight increases
Solution Approach 1:
The flight control system automatically monitors rotor RPM and provides tactile feedback through the collective stick to guide the pilot back to safe operating parameters. The system serves itself by using the existing control interface (collective stick) to provide both primary control function and overspeed protection, eliminating the need for additional complex automation while reducing pilot workload.
Solution Approach 2:
The system continuously monitors rotor RPM and provides real-time tactile feedback to the pilot through variable friction resistance on the collective stick. When overspeed is detected, the system applies a breakout force that increases resistive force, creating an intuitive tactile cue that guides the pilot to increase collective pitch and reduce rotor speed, thereby closing the control loop without requiring pilot instrument scanning.
2Reliability
If the flight control system provides continuous tactile feedback through the collective stick to prevent rotor overspeed, then rotor speed control is improved, but the device complexity increases
Solution Approach 1:
The collective stick serves dual functions: as the primary control for adjusting collective pitch and as a feedback interface for rotor overspeed protection. The same control element that the pilot uses for normal flight operations also delivers the protective tactile cues, eliminating the need for separate warning systems or additional control mechanisms.
Solution Approach 2:
The flight control system uses the existing collective stick mechanism to provide overspeed protection, rather than requiring a separate dedicated protection system. The system leverages the pilot's existing interaction with the collective stick to deliver protective feedback, thereby achieving enhanced reliability without proportionally increasing device complexity.
3Loss of information
If the flight control system provides tactile cues through the collective stick for rotor overspeed protection, then pilot awareness of rotor speed limits is improved, but the need for instrument scanning increases pilot workload
Solution Approach 1:
The system provides continuous tactile feedback through the collective stick that directly correlates with rotor speed status. The variable friction resistance and breakout force create an intuitive physical cue that informs the pilot of approaching or exceeding safe rotor RPM limits, eliminating the need for the pilot to visually monitor instrument readings and reducing cognitive workload.
Solution Approach 2:
Instead of requiring the pilot to actively monitor instruments to detect rotor overspeed conditions, the system inverts the approach by passively providing tactile cues that guide the pilot back to safe parameters. The control interface itself communicates the status and desired correction, reversing the traditional model where the pilot must actively interpret instrument data.
Data Source
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AI summary
A flight control computer (FCC) (205) for a rotorcraft (101) includes a processor and a non-transitory computer-readable storage medium storing a program to be executed by the processor, with the program including instructions for providing main rotor overspeed protection. The instructions for providing the main rotor overspeed protection include instructions for monitoring sensor signals indicating a main rotor RPM, determining a target operating parameter, determining one or more flight parameters in response to a relationship between the main rotor RPM and the target operating parameter indicating a main rotor overspeed condition. Determining the one or more flight parameters includes determining a setting for a flight control device (107; 212) of the rotorcraft (101) that changes the main rotor RPM, controlling positioning of a pilot control according to the flight parameters, and controlling the flight control device (107; 212) of the rotorcraft (101) according to positioning of the pilot control.