Helicopter Airspeed Blending for Accurate Low-Speed Control
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Solution Overview
Problem
Existing airspeed measurement systems for rotary-wing aircraft, such as pitot probes, are not accurate at low airspeeds due to factors like large rotor downwash, high angles of attack, and poor signal-to-noise ratio, leading to degraded handling qualities, performance, stability, and efficiency.
Innovation Solution
A method and system that determine a blended airspeed by combining data from pitot probes with rotor control commands, using fade values to adjust the confidence levels of measured and estimated airspeeds, thereby improving accuracy at low airspeeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pitot probes are used to measure airspeed, then airspeed measurement is reliable at high speeds, but measurement precision deteriorates at low airspeeds due to rotor downwash and poor signal-to-noise ratio
Solution Approach 1:
The patent combines multiple airspeed measurement methods (pitot probe measurements, radar measurements, and control input-based estimates) into a blended airspeed value. This merging allows the system to leverage the strengths of each method while compensating for their individual weaknesses, particularly improving low-speed measurement reliability by combining pitot data with radar and estimation data when pitot alone is insufficient
Solution Approach 2:
The system dynamically changes the weighting parameters of different measurement sources based on flight conditions. At low airspeeds, it increases reliance on radar and estimation data while reducing reliance on pitot probe data. The blending algorithm adjusts parameter weights continuously to optimize measurement precision across the full airspeed range
2Ease of operation
If control settings are adjusted to react to low airspeed changes, then handling qualities improve, but system complexity increases due to need for reliable low-speed airspeed data
Solution Approach 1:
The flight control system automatically performs the complex task of blending multiple airspeed measurements and determining appropriate control settings without requiring manual intervention from the pilot. The system self-adjusts control parameters based on the blended airspeed data, improving handling qualities while masking the underlying complexity from the operator
Solution Approach 2:
The system implements continuous feedback loops that monitor blended airspeed measurements and automatically adjust control settings accordingly. This feedback mechanism enables the helicopter to respond efficiently to low airspeed changes while the complex blending and adjustment algorithms operate automatically in the background
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
The blended airspeed approach enhances the accuracy of airspeed measurement at low speeds, allowing for more efficient control settings adjustments, improved performance, stability, and efficiency of rotary-wing aircraft.
Implementation Method 1
Pitot probes function by comparing the pressure in a tube facing the direction of travel of the aircraft to the static air pressure.
Data Source
AI summary
A method for controlling a rotary wing aircraft includes determining a measured airspeed of the rotary wing aircraft based on data from a pitot probe, determining an estimated airspeed of the rotary wing aircraft based on rotor control commands, and determining a blended airspeed based on both the measured airspeed and the estimated airspeed.