Speeding Up Fan Blade Integrity Testing With ARAMIS

Aircraft maintenance, repair and overhaul (MRO) operations ensure that aircrafts are always safe to fly during their whole service life. An integral part of any aircraft maintenance scheme is the engine repair and overhaul.

Especially, fan blades of modern aircraft propulsion turbines have to withstand extreme operating conditions during their service life. To guarantee the highest possible level of safety, fan blades are continuously checked for their integrity. Furthermore, fan blades are exposed to lightning, ice and bird strikes. Incidents like these trigger the so-called long service inspection during which defective fan blades need to be identified and replaced. This procedure is costly and time-consuming as it includes the complete disassembly of the turbine. During the time of the service inspection, an expensive exchange turbine will keep the aircraft up and running. Obviously, airlines want to reduce the downtime of their jet engines to a minimum.

A fast inspection of each fan blade without the need to disassemble the whole turbine would save a lot of time and money. Imagine the service technician could carry out a measurement on each fan blade with a quick response on the state of the component – safe to fly or not?

Here, ZEISS's 3D testing sensor ARAMIS enters the stage. Using the point tracking technology of ARAMIS, the fan blade’s reaction to hammer impact tests can be evaluated and used for the calculation of the ODS (Operating Deflection Shapes) of the individual fan blade. The comparison of the actual measured operating deflection shapes to the simulated mode shapes or the actual state from past measurements of the fan blade allows drawing conclusions on the integrity of the component. If there is a shift between measured and simulated mode shape or a complete change in the characteristic resonances (for example, over life), then there could be a crack somewhere in the blade and it needs to be replaced.

ZEISS carried out a study on a single fan blade to prove the general feasibility of the concept. Let’s take a closer look at the steps of the process.