Aircraft Static Pressure Position Error Correction via CFD
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Solution Overview
Problem
Static pressure measurements on aircraft are influenced by geometry and configuration, leading to position errors that vary with flight variables, necessitating accurate correction for safe air traffic management, especially at high altitudes where vertical separation is critical.
Innovation Solution
A method using Computational Fluid Dynamics (CFD) and flight tests to determine a position error correction model, represented by a polynomial function, which corrects static pressure measurements without requiring aircraft modifications, by calculating non-dimensional pressure coefficients and validating with ground station measurements, and further tuning through varying speed runs and steep turns to cover a wide range of flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If static pressure measurement is used to determine altitude, then air traffic management can be handled with standardized flight levels, but position errors occur due to aircraft geometry and configuration influencing the flow field
Solution Approach 1:
The patent applies parameter changes by developing correction models that account for variations in aircraft geometry, configuration, angle of attack, sideslip angle, Mach number, and Reynolds number. These parameters are measured and used to select appropriate correction values from pre-determined correction surfaces, thereby compensating for position errors in static pressure measurements without modifying the fundamental measurement system
Solution Approach 2:
The patent introduces correction models and correction surfaces as intermediary elements between the static pressure measurement and the final altitude determination. These correction models, which incorporate aircraft-specific geometric and configuration parameters, act as mediators that transform the raw static pressure measurement into a corrected value that accounts for aircraft-induced flow field distortions
2Measurement precision
If position error correction is implemented for each aircraft, then vertical separation accuracy improves to 1000ft flight level separation, but measurement and calibration complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-determining correction surfaces for multiple aircraft types through ground-based wind tunnel testing or CFD simulations before actual flight operations. The correction models are established in advance for various aircraft geometries and configurations, allowing flight systems to simply query and apply the appropriate correction values during operation without performing complex real-time calculations or additional calibration procedures
Solution Approach 2:
The patent implements a practical level of correction by focusing on the most significant parameters (angle of attack, sideslip angle, Mach number) and using pre-determined correction surfaces for discrete aircraft configurations. This partial action approach provides sufficient accuracy for 1000ft flight level separation without requiring correction for every possible minor variation in aircraft state, thereby balancing precision requirements with system complexity
3Measurement precision
If aircraft modifications are made to improve static pressure measurement accuracy, then measurement precision improves, but manufacturing cost and aircraft complexity increase
Solution Approach 1:
The patent applies the copying principle by creating detailed digital representations (correction models and surfaces) of aircraft geometric and configuration parameters without physically modifying the aircraft. These digital copies capture the essential characteristics needed for correction calculations, allowing accurate position error compensation through software-based methods rather than hardware modifications to the static pressure measurement system itself
Data Source
AI summary
The invention provides a method for determining a position error correction on a static pressure measurement at an aircraft flying through a flow field by means of a Taylor expansion series. The method comprises determining the constants of such a Taylor expansion series by the successive steps of an initial determination using computational fluid dynamics and a 3D scan of the aircraft, a validation of the results by low altitude flyby's at a ground station and an extrapolation of the results to altitude by performing flight tests at constant altitude and conditions of constant atmospheric pressure.