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Engine maintenance

Endoscopic testing and repair processes

Photo: Rolls-Royce Deutschland Ltd & Co KG

It is the aircraft engine that is especially relevant for non-destructive testing and repair processes, but at longer intervals also the visual inspection of landing gear and fuel tanks. For complex demands in repair and maintenance, SCHÖLLY has developed relevant technology modules in close cooperation with, among others, the engine manufacturer Rolls-Royce Deutschland Ltd & Co KG in the aviation research program “LuFo" of the Federal Ministry for Economics and Technology.

Problem: Engine damagage from foreign objects

Because of the enormous acceleration, foreign bodies or the remains from a bird strike that get into the engine during operation become projectiles and can cause damage of various extents (Foreign Object Damage, FOD). Since the replacement of engine parts represents a great time and cost factor, repair work is the first choice, as long as the work does not compromise the safety and performance of the aircraft. Damages considered repairable, for example, are small cracks and impact nicks on the turbine blades. 

Repairs by Boro-Blending

SCHÖLLY is a competent technology partner when dealing with the development of repair solutions for engine damage. Damage to turbine blades can, for example, often be repaired by a special process called "Boro-Blending". The damaged material is removed and a continuation of the crack and the subsequent peeling away of material are effectively prevented. With this process, complicated disassembly and a longer malfunction of the turbine can be avoided.

Suitable products: Flexible Borescope Blending Tool

Problem: Impurities in the cooling air system

The cooling air system can be contaminated by such substances as volcanic ash or sand entering the turbines during operation. Foreign particles settle on the nozzle guide vanes (NGVs) behind the combustion chamber and melt due to the high temperatures. In time, the deposits can clog the cooling holes of the NGVs (illustration on the left). The parts then are insufficiently cooled, which leads to localized melting and to the necessity of replacing the NGVs. In addition, high temperatures result in reduced performance of the engine and quicker material wear of further components inside the engine.

Solution: Cleaning of nozzle guide vanes (NGVs)

SCHÖLLY develops solutions that serve to clean the NGVs in the engine. Integrated into an endoscope, a cleaning function can remove the deposits from the NGVs. So a time-consuming and expensive disassembly of the engine to replace components can be avoided. In addition to a camera module and LED illumination, the endoscope system has a central high pressure nozzle. With water pressure of several 100 bar, persistent impurities and dirt can be effectively removed. Various functions can be integrated into the endoscope solution as required. Automated solutions can be developed on request.

Further information: Visualization PLUS

Repairing or replacing engine components

Replacing components in an engine requires great time and expense. When defective parts are being replaced, the aircraft cannot be used and high costs are incurred for the operator. For the maintenance of engines, the manufacturers have set specific repair guidelines. Exact definitions are listed in what cases a part can be repaired or must be replaced. The size and the position of the defect play an important part.

Highly precise measurement of defects

SCHÖLLY develops endoscopic solutions that allow for highly precise measurement inside engines. By means of a novel measurement function, the size of defects inside machines can be exactly determined and the specifications of the manufacturer can be reliably checked in the case of damage, capable of exactly determining damage or indentations in a size range of 50 μm to +/-5 μm. Precise measurement determines whether and how long further operation is possible. 

Further information: Visualization PLUS