A technique for reducing supersonic transient loads on internal wind tunnel balances

Design of slender supersonic missiles requires a comprehensive experimental support in the form of wind tunnel data for a wide range of flight parameters (angle of attack and Mach number). However, in supersonic wind tunnel testing, the problem exists of transient loads at the times of the starting and stopping of the supersonic flow. In the environments of pronounced transient loads, characteristic of blowdowin wind tunnels like the T-38 of the Military technical Institute in Belgrade, it is necessary to provide control of the use of internal wind tunnel balances in the permitted design load ranges. The presented technique is related to the definition and implementation of a methodology for reducing the transient loads on wind tunnel balances in supersonic wind tunnel tests. By limiting the clearance between the model and its tail support (sting) to a magnitude which permits normal tests, but results in model-support contact during the excessive loads, part of the loads is transferred to the support sting, relieving the balance. The technique improves control over the wind tunnel test process, improves measurement accuracy and prevents damage to sensitive instrumentation (wind tunnel balances).