Restoration of Dimensional Tolerances

When the inner diameter (ID) of aluminum landing gear outer cylinders is worn or damaged there is very little that can be done to repair the damage consequently the outer cylinder has to be condemned and taken out of service. The aircraft industry condemns many aluminum strut outer cylinders at a high cost. The cost to the USAF alone is of approximately $3M per years. The main cause for condemnations is that the ID of the cylinders is over sized due to wear or a deep scratch cause by failure of an internal component. Chrome plating and various thermal sprays can be used to repair steel outer cylinders when they are damaged, unfortunately there is very little that can be done to repair a hard anodized surface. A coating repair which builds up thickness and can be machined /ground to size, like chrome plating, for aluminum cylinder IDs would be a great value to the aircraft industry. The coating would have to be able to seal hydraulic fluid and high pressure nitrogen. It would also have to be able to handle high loads without spalling off. If a repair method could be developed then a considerable savings could be realized by the aircraft as well as improved supportability to the fleet. Physical Vapor Deposition (PVD) or magnetron sputtering technology has the potential to apply the same series of aluminum onto worn aluminum outer cylinders and possibly other aluminum parts. Magnetron sputtering process is currently used to apply thin coatings (0.001 inches) of aluminum on steel landing gear parts for corrosion. This process can be modified to be able to apply thick coatings (0.008-0.010 inches) of same series aluminum onto the ID of aluminum outer cylinders. This coating then can be machine, anodized and honed to bring the outer cylinder back to serviceable condition.