RUAG relies on HBM solutions in wind tunnel testing

The model is equipped with a RUAG six-component balance to obtain the global forces and moments acting on the aircraft. The aircraft is driven by two powerful wing mounted propeller turbines. The propellers will have a significant effect on the airflow around the wing and must thus be incorporated in the wind tunnel model. The forces acting on the propellers are measured with additional 6-component balances installed in the hub of the propellers (Rotating Shaft Balances). From these global force values, the aerodynamicist extracts information about the performance of the aircraft but also its stability and controllability. 

Structural engineers may be more interested to obtain the aerodynamic loads on certain components of the aircraft. Such data is derived from pressure measurements at different locations on the model. For this purpose, the LOSITA model was equipped with more than 700 pressure taps. An alternative or complementary approach is the use of strain gauge component balances designed specifically to measure, for example, the forces on a single control surface.

A six-component balance has the task of measuring three orthogonally aligned forces and moments simultaneously with as little mutual interference as possible. In aviation, these are lift/normal force (Z), drag/axial force (X) and side force (Y), and the moments around the roll (L), pitch (M) and yaw (N) axes.

The RUAG balance consists of two halves: the earth-fixed or non-metric and the metric half.

• Non-Metric Half: It is attached to a solid structure, e.g. the ground or a support, which determines the position of the model in the wind tunnel.
• Metric Half: It is fixed to the object to be measured, i.e. the car or aircraft model.

Via connecting rods and measuring elements with high-precision strain gauges, mechanical strains are recorded electrically and converted into physical units via a preceding calibration.

RUAG’s 7xx Balance Series

Since the customer requirements on the test object and the forces to be measured are directly dependent on the size of the wind tunnel model, the RUAG balance family offers the possibility of selecting an optimally suited balance for the test in terms of volume and load range.

Annual calibrations, traceable to a national standard, are required for ISO 9001 quality assurance. This applies to the MGCplus systems used as well as to the RUAG multi-component balances.

A calibration system has been developed for this purpose, with which all MGCplus channels can be checked and calibrated. A DMP40 from HBM is used for the calibration of the balances, which meets the very highest requirements.