Mobile task force against rust

Unique repair procedure for landing gear components

Safety standards require that aircraft are subject to regular maintenance and overhauls. These procedures are very time and cost intensive. The service intervals are determined so that the aircraft do not need to be taken out of normal flight operations. This means that work is carried out, as a rule, in the short time intervals between flights or overnight. In the case of unscheduled maintenance work, for example if corrosion is detected in the landing gear, the normal ground time of the affected aircraft can be overrun significantly. Major landing gear repairs can take several days or even weeks. Effective maintenance has therefore become a significant value creation factor. It makes a definitive contribution to cost saving and to ensuring the customer's commercial success.

In order to efficiently repair damages to undercarriage components as part of maintenance events (C-Check), Lufthansa Technik has developed a mobile reaming and milling process for Airbus A330/340-200/340-300 aircraft, known as "Quick Mill Repair". "Quick Mill Repair" is an integral element of the AST® Landing Gear services for rapid repair to landing gear components. This means that only the shock strut has to be removed from the nose undercarriage, so that a locking ring can be fitted over the cylindrical main fitting. Three openings in the locking ring are used to fit it to the main fitting, whilst corrosion is removed with precise reaming and milling work through a fourth opening. The positioning of the locking ring can be adjusted so that work can be carried out on all four holes in the main fitting.

Ideally, four openings in the locking ring are positioned above four holes in the main fitting, so that all holes can be worked on in a single step. Corrosion on the hole and bevel (chamfered outer edge of the hole) is first removed manually by reaming using a hand reamer and then milled or turned with a hand drill. During this work on the bevel, callipers are used to ensure the correct depth and thickness of the bevel. The new "Quick Mill Repair" process enables repairs for an inner diameter of 29.0 to 31.4 millimetres. Bronze prefabricated bushes in size gradations of 0.5 millimeters are delivered with the repair work and inserted after the repair has been carried out.

After the landing gear component has been freed of corrosion, it has to be inspected for even the smallest damages and cracks. This is followed by curing the metallic surface with shot blasting to produce balanced surface tension. A highly corrosion-proof cadmium plating is then applied, along with a coat of primer to provide corrosion protection. After the bushes are mounted, another coat of primer is applied. Only then can the prescribed aviation safety certification take place and the aircraft resume operations.

As soon as a report of corrosion is lodged, the Lufthansa Technik Airline Support Team (AST ® )team sets off – at the very latest the following day – to get to the corrosion under control. One of three specially trained mechanics and a crack inspector fly to the customer aircraft, taking the tool as freight with them. In an ideal case, the repair can be carried out within a single day. This represents an enormous saving for the customer in terms of both time and cost for the customer when compared to the 7-14 days required to dismount, transport, repair, and reinstall the undercarriage when using conventional techniques. The patented repair procedure, already proven more than 20 times, requires neither electricity nor water. The repair can thus be carried out manually and with complete flexibility anywhere in the world. A tool suitable for use on the Airbus A330/A340-500/A340-600 has already been developed and is ready to be put into service.