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Japan Aerospace Exploration Agency

Diagnostic technology for the aerodynamic characteristics of actual aircraft


March 31, 2015
Main wing deformation measured during Hisho flight

In March 2015, JAXA performed operating tests on a high-altitude, turbocharged engine at its Chofu Aerospace Center.

While the most common type of aircraft engine is the gas turbine type, with its compact size and high levels of output, JAXA is exploring the idea of using reciprocating engines (diesel engines) in unmanned aircraft with long-endurance capabilities. Reciprocating engines may be heavier than their gas turbine counterparts, but they also boast high levels of fuel efficiency that make it possible to reduce the amount of fuel ...[more]

Aircraft and spacecraft developments were conducted using ground-based prediction tools like wind tunnel testing and computational fluid dynamics (CFD) to predict the aerodynamic characteristics of actual vehicles.

Ground-based prediction sometimes fails to capture the aerodynamic characteristics of actual aircraft, since the prediction includes phenomenological and modeling differences from actual aircrafts in terms of Reynolds number (the ratio of inertial forces to viscous forces) effect, detailed configuration differences, deformation during flight, and mathematical models of fluid phenomena. On the other hand, aerodynamic data acquired from flight tests may be limited compared with ground-based testing, but they can provide key information to improve the prediction tool based on ground testing using comparisons of aerodynamic characteristics from flight tests and ground tests.

This study focuses on developing technologies that make it possible to visualize and identify the positions of shockwaves on the upper surface of an aircraft wing, which have a sizable impact on aerodynamic characteristics in actual flight tests, technologies that enable users to conduct detailed pressure distribution measurements, and technologies for gathering extensive data on wing deformation.

The wing deformation measurement system on the jet flying test bed, "Hisho" : Two cameras installed on two windows to obtain three-dimensional geometry of markers (black circles) on the wing