Ground Vibration Test at National Test Pilot School

Pilots at the National Test Pilot School conducted a Ground Vibration Test (GVT) on an Aermacchi MB-339, a military jet trainer and light attack aircraft to analyze its dynamic behavior under varying conditions. The test utilized the high channel Spider-80Xi system with the EDM Modal suite to perform the Ground Vibration Test. Seven accelerometers captured the aircraft's response, while a modal shaker excited the structure, enabling the measurement of frequency response functions (FRF). A Burst Random excitation method was applied, and the data was processed using the p-LSCF frequency domain curve-fitter (Poly-X) to determine the aircraft’s modal parameters accurately.

Some pictures and results from the experiment are illustrated below.

Ground Vibration Tests (GVT) are conducted to assess aircraft flutter and establish a safe flight envelope before takeoff. The results from these experimental modal tests are also essential for correlating and validating simulation model outcomes. As such, GVT is a critical step in the aircraft development and assembly process.

Crystal Instruments’ Ground Vibration Testing system is efficient in handling these complex modal tests.