Mechanical Diagnosis and Prognosis of Military Aircraft: Integration of Wear, Vibration Time-Frequency Analysis and Temperature into Diagnosis Algorithms

In critical conditions, gears operate with insufficient lubrication and efforts are made to improve the life of these gears against wear. A local gear-tooth defect such as a fatigue crack, pit, or chip weakens a tooth and causes transient events in the system. The magnitude and duration of these events depend mainly upon the severity of the defect and the contact ratio of the gear pair. If the tooth fault severity is small and the contact ratio is high, the resulting transient may not show distinctively in the vibration signal; in such cases, a combination of vibration signals, time-frequency domain analysis, temperature, and other signals can be combined to reveal such events. This study presents a combined signal method for gear tooth failure prediction within the Tail Rotor Gearbox of an AH-64 helicopter under poor lubrication. From the investigation to date, a preliminary model of gear tooth failure resulting from a loss of lubricant has been fabricated. The present experiment will seek to more thoroughly quantify the present observations, and shall be analyzed further in future reports.