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High-tech paintwork at the Luftwaffe
By Patrick Hoeveler
Storms, dirt and heat: the paint used on fighter aircraft has to survive everything. After about 2,400 flying hours, the jets normally undergo a major overhaul. In the case of the Panavia Tornado, the fighter bombers come to Erding for a makeover at the hands of the paint experts of Air Force Maintenance Regiment 1 every seven to eight years.
 Before any painting can get under way, the aircraft has to be washed. After landing, it is defuelled and towed to a special hangar where four or five service personnel spend a whole day washing it with high-pressure spray guns and scrubbing it by hand, almost as if it were a car. The water used is then filtered to drinking water quality for reuse in washing.
After that the specialists prepare the jet for stripping of the old paint. All the flaps and apertures are sealed with adhesive tape and hot-sealing adhesive prior to bombardment of the surface with plastic pellets. Dry stripping of an aircraft requires up to 500 kilograms of pellets, which are made from industrial waste such as old light switch cases, sockets and the like. In Erding they reuse up to 90 percent of these pellets, as the material is collected on the ground and sucked up.
As Flight Lieutenant Herbert Messner of Air Force Maintenance Regiment 1 points out, “It is important that all the paint comes off in the process.” In the operational unit it is not unusual that, due to the need for repairs, the maintenance staff end up painting over the same spot four or five times. “As a result, hairline cracks can go unnoticed. Then the water can penetrate and cause corrosion.” Once the paint has been removed, the surface has to be reground by hand and the grinding dust washed off before the combined application of etch primer and corrosion protection can commence.
The regiment takes health and safety at work and environmental conservation very seriously. Hence ultra-modern facilities are used. For example, for small parts there is a separate spray station in which the air supply is controlled through louvers. An air lock ensures that no fine paint particles can escape outside.
Painting of the aircraft takes place in one of two identical docks, whose temperature and humidity are computer regulated in accordance with current requirements. The air flows in horizontally, preventing the formation of droplets and ensuring that the undersides are properly dried as well.
Now for the paint process itself. Since October last year the magic formula for Warrant Officer Christian Waldinger, subunit leader Surface Treatment, and his colleagues has been “2K PUR”. The new paint contains two components, polyurethane and acrylate. The main advantage of this lies in its resistance to heat. As Waldinger explains, “The paint previously used, which consisted of only one component, can withstand temperatures of up to 70º Celsius, whereas two-component paint can survive over 200 degrees. It has also proved to be very tough. Hydraulic fluid and oil cannot eat into the paint.”
However, the painting operation takes two to three times as long as with the old paint, which was safe to tread on after only 30 minutes. The two-component variant takes eight hours to dry. One coat for a Tornado (primer plus topcoat) requires up to 30kg of paint, which is applied with spray guns at a pressure of around 140 bar. During the process, the paint technicians pay close attention to the thickness of the coat, which has to be wafer thin at around 30µ to avoid flaking off.
Every year some 24 Tornadoes receive their new camouflage dress. The familiar green was replaced by the unit colour of medium grey some time ago, as these days the threat is primarily from the ground. But other considerations are also taken into account. To facilitate the removal of dirt, the degree of lustre required for a smoother surface is relatively high, at 20 percent. “The paint must last and deflect dirt. We now paint the undercarriage bays and flaps in grey instead of white,” says Waldinger. “Here too we use the two-component paint for protection purposes.” However, the inscriptions which, in the case of a Tornado, consist of some 150 warnings, continue to be added with a single-component paint so that they can also be applied by personnel in the units.
But the service personnel and staff in Erding have still more in store: as well as colourful special paints, they also create in next to no time elaborate markings in the form of films which can be stuck onto the aircraft as overlays. “That saves a lot of work,” says Waldinger. He creates the relevant graphics on the computer and they are then printed out on a cutting plotter to a width of 1.4m and a length of up to 100m. If the markings are wider than this, the computer splits them up. In this way, it takes only 30 minutes, for example, to create the insignia for Operational Wing Mazar-e Sharif.
“We bought the cutting plotter for the Cougar helicopter. It allows us to process more jobs, and to a higher standard of quality,” says Flight Lieutenant Messner. The Special Transport Wing helicopter has to contend with the build-up of carbon thanks to the inclined layout of the engine outlets. This has to be concealed with the aid of paint. “Today we use nano-like technology. The dirt can be easily wiped off the shiny and almost smooth-as-glass surface with a wet cloth,” explains Waldinger. Moreover, the paints produced by the MIPA company from Essenbach near Landshut permit weight savings of 50kg. The design proposals for painting the Cougar came from the Luftwaffe unit. In this way, the full package proved considerably cheaper than similar offerings from industry.
From FLUG REVUE 8/2007
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