4. IPCT Ground Vibration Measurements on a Small Aircraft

One of the AIM subtasks required the measurement of structural vibration using IPCT on a small aircraft. This has been done in an industrial environment on a Piaggio P 180, without interfering with production testing and other flight test activity. A ground test, simulating flight conditions and measuring wing vibration was initially done and, due to budget restrictions, only a limited IPCT flight test could be completed using the ground set-up. For the ground tests, a set of accelerometers was also installed to compare the IPCT results with those obtained with traditional means. For these tests, an exciter, driven by a PC, was placed at the wing tip to generate a signal at the desired frequency. With this system, a frequency sweep was performed around the known natural frequencies, exciting the first wing bending mode. Furthermore, accelerometers were installed on the camera support in order to evaluate whether the camera itself was vibrating. During ground testing, the IPCT method showed promising results for in-flight testing, although the resolution was insufficient for the higher frequency, lower amplitude results. These limitations would require supplementing any IPCT system with traditional accelerometer measurements. In what follows, a brief description of the test set-up, the test instrumentation, the data analysis and the results of the ground vibration measurements will be presented.