VIBRATION MONITORING TECHNIQUES INVESTIGATED FOR THE MONITORING OF A CH-47D SWASHPLATE BEARING

The vibration monitoring of U.S. Army rotorcraft is of current interest. Different systems and techniques are being investigated for use in mechanical fault detection. One of the requirements from a Health and Usage Monitoring System is the ability to detect gear and bearing faults using vibration data. This paper outlines the technical approach and the results from vibration testing of CH-47D swashplate bearings. The topics covered in this paper include the challenges of mounting an accelerometer to the swashplate, the Vibration Management Enhancement Program data acquisition system, the measurement setups and the fault feature extraction algorithms. The techniques for bearing fault detection will be presented in detail. These techniques include classical bearing fault spectral analysis, spectral based energy analysis, Power Cepstrum analysis, and amplitude demodulation envelope analysis. Test data and results will be presented from a seeded fault bearing test rig and compared to actual aircraft test data.