Rotorcraft VRS Protection Using Power Margin and Airspeed Control
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Solution Overview
Problem
Rotorcrafts face challenges in avoiding the vortex ring state (VRS) at low airspeeds, where vertical performance is compromised, and it is difficult for pilots to detect the onset of VRS, especially in poor visibility or high workload conditions, leading to control limitations and restricted ability to arrest high descent rates.
Innovation Solution
A flight control system that monitors vertical speed and compares it to a safety threshold, performing VRS avoidance by determining the power margin available from the rotorcraft's engines, limiting vertical speed if the margin exceeds a threshold, and increasing forward airspeed if it does not, thereby preventing entry into the VRS region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional pilot training and manual warnings are used to prevent VRS, then pilots are taught avoidance techniques, but pilots cannot detect VRS onset in poor visibility or high workload conditions
Solution Approach 1:
The flight control system automatically monitors flight parameters and detects VRS conditions without requiring pilot awareness or intervention. The system serves itself by using onboard sensors and processors to detect, evaluate, and respond to VRS conditions autonomously, eliminating the detection difficulty faced by pilots in poor visibility or high workload conditions.
Solution Approach 2:
The system continuously monitors vertical speed, forward airspeed, and power margin, comparing these parameters against VRS boundaries. When VRS conditions are detected, the system provides automatic feedback by adjusting flight control parameters to prevent entry into or recovery from VRS, creating a closed-loop control system that enhances detection and response reliability.
2Reliability
If automatic VRS protection systems are implemented, then VRS prevention reliability is improved, but flight control system complexity increases
Solution Approach 1:
The flight control system performs multiple functions: it monitors vertical speed, forward airspeed, and power margin; compares these against VRS boundaries; and automatically adjusts flight parameters to prevent VRS. By integrating these functions into the existing flight control system rather than adding separate dedicated systems, the patent achieves enhanced VRS prevention reliability while minimizing the increase in overall system complexity.
3Reliability
If transient control inputs are applied to prevent VRS, then VRS prevention is achieved, but the flight path of the rotorcraft may be affected
Solution Approach 1:
The system applies control inputs that are sufficient to prevent VRS entry or recovery without excessively altering the intended flight path. By using partial action (applying only the necessary correction) rather than excessive correction, the system maintains VRS prevention reliability while minimizing interference with the pilot's intended flight path and maintaining ease of operation.
Data Source
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AI summary
A method for protecting a rotorcraft from entering a vortex ring state, the method including monitoring a vertical speed of a rotorcraft, comparing the vertical speed to a vertical speed safety threshold, and performing vortex ring state (VRS) avoidance in response to the vertical speed exceeding the vertical speed safety threshold. The performing the VRS avoidance includes determining a power margin available from one or more engines of the rotorcraft, limiting the vertical speed of the rotorcraft in response to the power margin exceeding a threshold , and increasing a forward airspeed of the rotorcraft in response to the power margin not exceeding the threshold.