OBJECTIVE: Develop a reliable acoustic emission monitoring capability to detect the very early stages of crack initiation and propagation in rotating gearbox components in real time. DESCRIPTION: Vibration techniques for monitoring the health of rotating components have been well established, but a key shortcoming is the capability to identify the initial damage states of crack initiation and short crack propagation. Acoustic emission techniques have been used for some time in monitoring the health of static structures. The technology holds promise for early detection of cracks in noisy applications such as rotating machinery, if techniques are employed capable of pulling the signal of interest out of background noise generated by turbine engines, rotors, propellers and the elevated noise levels of the gearbox. Certain highly loaded rotating gearbox components with fast crack propagation rates require early detection to mitigate risk. Critical, highly loaded components in aviation gearboxes include gears, splines and bearings; the health of these components is a key safety driver. Acoustic emission technology coupled with a responsive, real-time processing capability has the potential to meet the requirement for this early detection. PHASE I: Develop a method of collecting and identifying signatures characteristics of crack initiation and propagation for rotating gearbox components. Demonstrate feasibility of innovative algorithmic methods to isolate these signatures. PHASE II: Develop a prototype acoustic emission crack detection system utilizing algorithmic methods. Validate the acoustic emission crack detection system in a demonstration to quantify capability and accuracy to detect crack initiation and propagation in rotating gearbox components. PHASE III: Finalize the acoustic emission system health monitoring design with major DoD end users and airframe manufacturers and conduct qualification testing for the applications. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Robust health monitoring for noisy rotating machinery environments is very challenging and will provide great benefit for complex mission-critical machinery including aviation, transportation and industrial applications where early detection is key to ensuring safety of operation.