HIRF Transfer Function Observations: Notes on Results Versus Requirements and Certification Approach

HIRF transfer functions results are rarely available to the public. Generally, the data provided in applicable guidance material are used for estimation of internal HIRF environment in an air vehicle. An exemplary set of HIRF transfer functions for a small aircraft is presented here. Results for the aircraft (10.4-m wingspan and 8.3 m of length) are compared with regard to state of the art approaches applied for aircraft HIRF certification campaigns. This is done in appropriate frequency ranges and by the use of applicable test methods with regard to requirements in place. For all major types of contemporary test methods, results are generated by measurement and numerical computer modeling. Principles of outcomes are discussed and compared to current practice in place. This concerns the shapes of the transfer functions on one hand and the order of magnitudes of obtained levels on the other hand. The obtained results show significant deviations from generic transfer functions currently applied in aircraft industry. The coupling to the interior of the aircraft observed here was higher than indicated by the applicable generic transfer functions. Numerical computer modeling is used here to verify the obtained outcomes by principle.