Helicopter air data systems calibration using DGPS

Abstract

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This work presents and analyzes the suitability of using differential GPS equipment (DGPS) for the determination of air data system errors by means of flight testing of the H-50 (AS 350) helicopter. Since the Pitot-error cannot be undervalued, two existing methodologies that use the DGPS as a data acquisition tool have been adapted for the usage in helicopters. Results of flight tests using a validated technique (tower flyby and ground speed course) are presented for the purpose of comparison with data obtained from both proposed techniques. Data are processed through mathematical equations and specific code in MatLab® platform, which has been adapted specifically for this research. Two methodologies using DGPS are set: the first needs three stabilized legs for each speed within the desired flight envelope whose trajectory describes a path similar to a clover leaf, which suggests the method's name: "cloverleaf"; The second uses acceleration and deceleration in 90 degrees alternated legs forming a windbox-like design. The data reduction is performed by iterations of the estimated parameters until a convergence criterion is reached using the analysis of the outputs. Results show the suitability of both proposed methods from a quantitative point of view. Qualitatively, the windbox maneuver with parameters estimation from the analysis of output-error allows reducing material resources expenditures without quality degradation.