Development of national MRO capability for a basic trainer aircraft: flight and ground tests

Patria has an ongoing program to develop a partial national MRO capability for the new basic trainer aircraft of the Finnish Air Force (FINAF). The capability is developed since no original design data is available for Patria. This paper presents the research done on the flight tests and static ground tests of individual components as two subprojects of the MRO capability program. The flight test subproject, including ground calibrations followed by 22 flights covering the whole flight envelope with one instrumented aircraft, was carried out in cooperation between Patria, FINAF and VTT. The data from the instrumentation suite including 40 strain channels, 8 temperature sensors and various flight parameter sensors was successfully captured for later analyses. From the flight test data, control surface loads were directly calculated using calibration results. Global loads were calculated using a neural network analysis. Flight test results have already been utilized when designing repairs and modifications for the aircraft. The ground test subproject was carried out in cooperation between Patria, VTT and TAU. For the ground tests, the instrumentation of the aircraft components was extended to a total of 260 strain channels. In addition, 6-8 displacement sensors were used per component. The full-field deformation data from the areas of interest of the components was captured simultaneously using Digital Image Correlation (DIC). During the ground tests, all major components of the aircraft were individually subjected to 11-35 static load cases in a test jig and structural responses (loads, strains, and displacements) were measured. In this paper, the setup, the load cases, and the results of one or two significant components are discussed. Results obtained with different techniques are compared to assess the applicability of DIC also in the future. The ground tests provided useful data since linear responses were measured from the components. The ground test results can be used later in the MRO capability program as a global FE-model of the aircraft is modelled and material properties of the aircraft components are determined with a combination of testing and analysis.