Vertical Lift Aircraft Rotor Fault Detection is a process that uses rotor blade tracking revolution to revolution (rev-rev) data to identify faults and/or failures from the data stream.

Blade tracking takes data from the rotor system at very high speeds and typically averages the data stream to identify the relative blade height and lead lag for each blade. Dynamic blade motion and other fault indicators are encapsulated in the data and generally have been discarded and/or ignored through the averaging process. Blade track data sets are very complex and have been difficult to use for fault detection. Primary accelerometers and other sensors not attached to the rotor’s rotating frame generally cannot detect faults or failures such as pitch link bearing wear, failing elastomeric bearings, and other wear related maintenance issues.

The rev-rev process uses commercially available vertical lift rotor tracking devices to take dynamic data directly from the rotor blades. The information derived is directly relatable to specific parts of the blades and rotor head. Dynamic data are taken from two or more flight conditions. The fault and failure detection rev-rev process takes into account and allows for the identification of system control inputs, dynamic environmental variables, tracking sensor motion, and the ability to evaluate the range of motion of key rotor components. The rev-rev process smoothes and segregates the tracking data into non-complex sets of data that are used for fault detection. The process is broken into modules that allow for rapid rotor evaluation and recommendations for maintenance actions. The data collection and/or analysis can be made part of the aircraft’s Health and Usage Monitoring Systems (HUMS) or transferred to off-aircraft analysis. The rev-rev process analyzes the collected data in a few seconds. The analytical output allows for a very comprehensive wear analysis of the blades and rotor system over time, and can be used to provide clues for extending or executing "On-Condition" maintenance of the aircraft.

A significant amount of research has been done on dynamic flight data and it indicates that faults can be isolated through the rev-rev process. Analysis of faulty elastomeric assemblies is possible. Early detection of bearing wear and faulty damper isolation is possible through range of motion analysis. Dynamic blade balance on the helicopter is possible. Blade pitch angles can be calculated and analyzed for any flight regime.

The overall cost of vertical lift aircraft rotor system and rotor blade maintenance is significant when considering the operating cost of the aircraft. The ability to isolate, locate, and predict faults and failures in a dynamic system is critical to the efficient and effective operation of the aircraft. Rev-Rev tracking data analysis provides early fault identification and elimination, significant operating cost reduction, and provides safer operation of the aircraft.