With their red safety harnesses around their shoulders and black safety belts between their legs, Roman Peper and Markus Roggmann could easily be taken for models advertising an indoor climbing venue, particularly as the two are moving around at a height of 18 metres.
However, the two men are not climbing a wall but are balancing, well secured, on the spine of the MD-11 Charlie Alpha. Peper and Roggmann are qualified painters at Lufthansa Technik in Hamburg and they are spraying the butt joints between the metal panels on the exterior of the aircraft with silicone to seal them. This has to be done before the aircraft receives a new coat of paint. Car drivers will be familiar with this technique from motorway bridges, where a rubber strip is placed between the steel beams and the road in order to balance out the differences in temperature. It is exactly the same with an aircraft.
Charlie Alpha looks like a seriously ill patient. It is covered in red sticking tape, while its landing gears are wrapped up in thick plastic foil and the outer skin has been stripped down to the metal. All the important openings and parts of the aircraft which must not come into contact with anti-corrosive agents or paint are covered with red tape to ensure they are absolutely watertight.
One of the first jobs when painting an aircraft involves removing the old paint - stripping - or "striptease", as the hangar staff call it. The outer skin of the aircraft is then sprayed with a paint-stripper based on formic acid. The outer skin swells up after ten to twelve hours and falls to the ground in fist-sized lumps. Day three and four of the repainting are taken up with unscheduled sanding work. In many places the old paint, particularly on the plastic components, was more badly affected than expected and the cracks were deeper than feared. Dieter Steinwender, Project Manager Aircraft Painting at Lufthansa Technik, has to rejig his schedule. But the trained electrician still hopes that he will manage to deliver the freshly painted MD-11 newly in eleven days, as agreed.
Dirk Trottnow, who works in the Signwriting department at Lufthansa Technik, has long since made his contribution to the repainting of the MD-11. After entering the height, length and width of the Lufthansa Cargo logo in the computer, he used the plotter to make the letters which will later be emblazoned along the length of 11,500 millimetres on the right and left of the cockpit. The individual letters, says Trottnow, are exactly 1,090 millimetres tall. Expresed in metres, the logo is 11.5 metres long and 1.09 metres in height. Only the Lufthansa logo on the tailfin is larger. The crane, after all, has a radius of 3.5 metres and therefore had to be produced in three sections.
Two rooms further along in the hangar, the paint for the MD-11 is ready and waiting: 600 litres of primer for two anti-corrosive coats, 200 litres of white paint, 160 litres of grey for the underside of the MD-11 and 40 litres of navy blue for the Lufthansa Cargo logo, the official registration D-ALCA as well as the crane on the tailfin.
Aircraft should be repainted once every five to six years. Unavoidable cracks in the paint - a result of severe stress - would otherwise endanger the construction of the entire aircraft. In order to keep unavoidable overspray to a minimum, the painters use special spray guns which electrostatically charge the paint. The aircraft then acts like a magnet and literally pulls the paint towards it. Despite the technology, painting is a fine art, says project manager Dieter Steinwender and testifies to his colleagues’ skills and adeptness: the aircraft is sprayed twice from left to right, once from top to bottom, then crosswise. And all that is done by a team that usually has 12 members - six on either side of the aircraft. Wrapped up in white protective overalls and equipped with breathing masks, the men are raised up and down on one of the six work platforms (or "flying carpets", as the Turkish colleagues call them) which are attached to the hangar roof.
The final painting phase does not take more than two and a half hours. "Including the two base coats of primer," Dieter Steinwender says, "painting only accounts for between five and eight per cent of our work." The rest is spent on the preparations: masking, stripping the paint, sanding, making the foils and weighing the paint. The latter is particularly important because saving weight is the be-all and end-all of flying. That is why the all the coats of paint together should be no thicker than a human hair. We will have about 0.12 millimetres," project manager Dieter Steinwender predicts. That corresponds to 450 to 500 kg of paint. Jürgen Heermann, a journalist and ex-flight engineer on a Boeing 747, once calculated meticulously that one more kg of weight on or in an aircraft requires an additional 200 litres of fuel per year.