Flight-to-Wind-Tunnel Correlation Study using JAXA’s Flying Test Bed “Hisho”

Abstract

Predicting aircraft flight performance using ground tests is important for development but difficult, and flight-to-wind-tunnel correlation methods have been developed and improved over many years. This paper examines the flight-to-wind-tunnel correlation of the aerodynamic characteristics of the Japan Aerospace Exploration Agency’s (JAXA) “Hisho” Flying Test Bed by applying typical methods to flight test data. It was found that the minimum drag coefficient of a business jet geometry test model follows the gradient of the Schoenherr equation well for forced turbulent flows. After that, the reference condition for the correlation was set, but discrepancies in the lift and drag coefficients remained between the flight and wind tunnel tests. A preliminary study identified force differences parallel to the axis of the engine nacelle as being caused by spillage drag due to the difference in the capture area ratio (CAR) between the flight and wind tunnel tests. However, the test data were insufficient to reasonably attribute the difference in the normal force component to lift yielded by the engine nacelle. This was due to the fact that the flight test parameters showed an interdependency and the effects of relevant parameters were not fully investigated in wind tunnel tests.