Product Divisions: Overhaul

Beauty more than skin-deep

Lufthansa Technik and its subsidiaries in Shannon (Ireland), Budapest (Hungary), Sofia (Bulgaria), Malta, Aguadilla (Puerto Rico) and Manila (the Philippines) and the joint venture Ameco Beijing (China) all perform regular overhauls of aircraft. These are the biggest and most labor-intensive maintenance events and can only be performed by maintenance organizations meeting special qualification requirements on the part of the aviation authorities.

The term overhaul refers to the Intermediate Layover (IL) check and the D-check. The IL-check lasts between two and four weeks and is carried out every three to five years. It is only required for certain aircraft types. To obtain easier access to the fuselage and wing structure for inspection purposes, a number of large assemblies such as the high-lift devices are dismantled. At the same time numerous items of equipment and systems are tested and repaired as necessary. Cabin components such as seats, galleys and toilets are also completely overhauled and, if necessary, the aircraft will be repainted.

The D-check is the general overhaul of an aircraft and hence the most extensive of all aircraft-related service events. This check is carried out every six to ten years and entails 30,000 to 50,000 man-hours of labor over a period of four to six weeks. Leading up to the overhaul, a widebody aircraft may have clocked up some 30,000 flying hours and 25 million kilometers.

During a D-check the entire structure is inspected down to the smallest detail. After that, the engines, the landing gear and the high-lift devices are dismantled, along with the cabin interior and the wall and ceiling panels. This is followed by removal of the instruments, the electrical systems, electronics and hydraulic and pneumatic equipment. All equipment dismantled and taken apart is closely scrutinized and any necessary repair work is carried out.

Every component is given a docket that states when and to where it has to be delivered in a serviceable condition in order for the aircraft to be finished on time. Once the aircraft has been stripped back to the "skeleton–, the outer skin with tens of thousands of rivets and the load-bearing structure of the aircraft can be scrutinized for damage and corrosion. Here, non-destructive testing methods such as eddy-current, ultrasonic and x-raying are used to detect the finest hairline cracks in the aircraft structure or its retaining elements.

For many aircraft types, Lufthansa Technik is able to test and repair all the components in its own workshops, in accordance with the philosophy of "better repair than throw away–. Accordingly, the engineers always start by trying to rectify damage on defective parts before buying in and installing new parts. Thanks to Lufthansa Technik's many decades of experience and its various official approvals from all the main aviation authorities, the repaired parts are then restored to a virtually brand-new condition. In this way Lufthansa Technik offers its customers efficient and cost-saving solutions for the overhaul of their aircraft without having to compromise on the reliability of components.

The repair of aircraft parts made from composite materials, such as radomes, wingtips, high-lift devices, landing gear doors, engine cowlings and thrust reversers, calls for an extremely high level of experience. These composite materials are becoming more and more widespread in the construction of modern aircraft due to their high strength and low weight compared with aluminum, for example. However composite parts are time-consuming to manufacture, so that new parts are particularly expensive. Lufthansa Technik was quick to recognize and to adapt this trend and has accordingly developed its own procedures for the repair of such components.