Keeping jets spic ’n’ span takes an ongoing effort

Aviation International News » November 2005
October 18, 2006, 6:24 AM

Just as with most elements of aircraft ownership, a good cleaning, inside and out, is much more involved than the average person could possibly imagine. Even showering down a piston single involves more than just putting on your bathing suit and grabbing a bucket and sponge. Cleaning solutions from the shelves of the local supermarket or Pep Boys won’t do. Regardless of aircraft size, using the proper materials and technique can make all the difference in the longevity of an aircraft’s paint finish, windows and upholstery.

For many operators, it’s just too large and specialized a job to do in-house. There is no shortage of cleaning and detailing services throughout the country that are eager to take on outsourced aircraft cleaning chores. One of the largest networks is Appearance Group, with 18 locations nationwide, six of which are in Texas. For a state-by-state directory, go to www.AircraftDetailing.com.

It should cost approximately $500 for an exterior wash and wax job on a King Air C90 (about five hours’ work) and as much as three times that for an aircraft the size of a Global Express (involving up to eight hours’ work). Experts recommend wet washing and waxing quarterly to maximize paint life.

Interior cleaning by a specialist ought to run about $200 for the King Air and about $400 for the Global. One of the reasons aircraft operators hire professional cleaners for interiors is that aircraft upholstery has fire-blocking coatings that can be compromised by some cleaning materials. Besides the safety aspect, sophisticated aircraft completion houses use high-grade materials such as silk and exotic wool blends that conventional cleaning products can damage or stain. The experts know what to use and where.

Some aircraft cleaning companies travel to the owner’s facility; others stay at their base and have the operator fly in. The former has an obvious advantage in convenience, unless the aircraft owner’s airport has restrictive environmental policies on waste water. Increasingly, airports are classifying wash-water runoff as hazardous material. That might not be the case at the airport where the cleaning company has its shop. Or at least, the company would have an approved wash stand and facilities and procedures in place to comply with regulations.

Insurance is another issue when contracting with an aircraft cleaning company. The industry standard is a $5 million policy to cover damage to the aircraft during the washing process. Experienced firms are savvy about what exterior cleaning materials to use and how to care for sensitive areas of the aircraft, such as Plexiglas windows and polished aluminum surfaces. Engine inlets, propeller spinners and leading edges of wings and tail surfaces–often called “bright work”–are also sensitive to the wrong cleaning products. One application of an improper chemical can dull their finish permanently.

There are some other caveats for those who might try to cut costs by hiring inexpensive, inexperienced labor: the first few washes might come out looking terrific and you’ll be tempted to believe you’ve beaten the system. It might take several washes, but by using the wrong solutions; incorrect cleaning rags and brushes; and improper techniques, those amateur aircraft cleaners could accelerate the deterioration of a paint job or interior upholstery, permanently dull the surface of bright work or, worst of all, cause windshields and windows to become hazy and yellowed.

Untrained cleaning personnel could also damage systems. For example, power washing landing gear could inadvertently wash away grease from bearings, inviting premature wear. Or an inexperienced cleaner might not know to cover the fuselage static port and compromise the system with water. They might fail to remove tape from a static port after finishing the job, causing improper instrument readings in flight, with predictably unpleasant results. Even after a wash and wax job by experts, a particularly thorough preflight is a good idea.

Whether you expect to hire an outside firm to clean your airplane regularly or plan to do it yourself, a working knowledge of some basic pitfalls will pay off. The fundamentals can be divided into several categories: cleaning materials–they need to be safe and effective for exteriors, interiors and windows, including heavier-strength degreasers for oily bellies and special products for removing the remains of bugs; applicators–the material should be safe for swabbing down the exterior without damaging paint; protective waxes–experts know what works best, lasts longest and best repels exhaust soot, runway grime and acid rain from the paint finish on your airplane; and technique–there are procedures that have proved to be the safest, most efficient sequence for washing and waxing a large business jet.

Wet Washing or Dry Washing?

With so many airports restricting traditional methods of wet washing, a number of products have emerged over the past several years for so-called dry washing. Wet washing, as you might imagine, involves soaking the airplane with a hose, brushing or swabbing its surface with soapy water, then rinsing it off–just as you’d do with the family dog or sedan. Dry washing is more like the waxing process. The cleaner is applied, either with a spray bottle or in a paste or liquid form, then wiped off. Dry washing has the added advantage of combining washing and waxing in the same process, but the tradeoff is that it takes less time for the finish to fade, so the process has to be repeated more often.

Earning Your pH Degree

Whether it’s wet washing or dry washing, using the correct cleaning solutions is critical. The key is ensuring the product used has the correct pH value–as close to the neutral 7.0 as possible–even lower in some cases. The higher the pH, the higher the acid content–good for cutting grease, but also good for attacking the relatively soft paints used on aircraft to retain flexibility.

As an example, typical home degreasing agents can have a pH of as high as 12.5. Even environmentally friendly products can have values higher than 9.5. If you’re doing it yourself, ensure that the products you’ve chosen are safe for the airplane’s skin. If you’re bringing in experts, test their expertise by asking the pH of their chosen cleaning solutions.

It’s also important to choose the correct applicators. Experts differ on what’s best to use, but the universal principle is to use as soft a material as possible. Some say it’s OK to use soft cotton terry towels for stubborn areas of painted surface, such as aircraft bellies or nacelles. Most say never use old T-shirts or even diapers. Apparently, what’s tender enough for a baby’s backside is still not gentle enough for your airplane. One aircraft cleaning service cites microfiber material as the only substance it will use for painted surfaces, including the final wipe down on bellies and nacelles after the gooey stuff has been removed with the cotton towels.

Paper towels are a complete no-no, say experts, especially on Plexiglas. And for those who were taught by their mothers the best thing to use for cleaning windows is newspaper, don’t bring that old wives’ tale with you to the airport. Wood-based material such as paper has no place cleaning anything whose surface is susceptible to scratch marks.

Prepping the Aircraft

With the appropriate materials on hand, experienced aircraft cleaners prep the airplane similarly to the way a pilot would perform a preflight inspection, starting from a fixed point and walking around the airplane covering static ports, wheel struts and other openings or components that might be damaged by water, cleaning materials or waxes and sealers. The walkaround is also a good time to make particular note of the locations of static wicks, pitot tubes and other components that could be damaged.

Next is the time to spray degreasers on areas that pick up oil, such as the belly or lower portions of engine nacelles. Allowing the solvents to soak the greasy areas is the prelude to the final wash–either wet or dry. This is also the time to apply cleaning solutions directly on the frontal surfaces of wings, empennage and the fuselage to remove bugs. It’s always better to remove bug residue after every flight, as soon as possible after landing. Allowed to harden, bug remains become that much more difficult to loosen. Further, what’s left of the bugs’ carcasses is highly acidic and can eat away at not only paint but also the aluminum skin beneath.

One aircraft cleaning specialist cites specific characteristics of certain models that require direct attention. For example, PT6-powered King Airs are susceptible to soot stains on the nacelles behind the exhaust pipes, on the wing leading edges and on the wing undersides. The more regularly those areas are cleaned of the soot, the easier it is to get them clean every time. The same cleaning specialist cited a propensity for Citations to develop a coating of oil on their undersides–a messy film that can become that much more stubborn to remove if left to coagulate over time.

Once the difficult areas have been “pre-cleaned” with stronger solvents and degreasers, it’s time to perform the overall wash. If it’s a dry wash, it matters little where one starts. Apply the cleaning solution systematically with soft applicators, then remove it as you go along. Different dry wash products recommend their own techniques. Some say to wipe off the material when it is still moist. Others recommend letting the solution dry completely.

When dealing with an airplane that has a tall T tail, start at the top, since residue from the tail can fall on the remaining portion of the airframe. While we’re back at the tail, it’s worth mentioning that aircraft cleaners should maintain high levels of safety consciousness when working so far off the floor. Bucket trucks are one way of accessing the tall tails safely. Scaffolding is another option. In either case, many aircraft hangars now install safety harnesses for workers to use when performing maintenance high off the shop floor. Washing and waxing an aircraft is a clear case for using a “trapeze” harness.

Whether dry washing or wet washing, avoid the windows with cleaning materials and applicators–whether using cloth, soft brushes or sponges. Some cleaning companies actually go so far as to mask windows during the washing process. Only materials specifically designed for aircraft windows should be used to clean Plexiglas windows and windshields. For simple cleaning after a low-level flight that claimed many bugs, soft soap and water will remove dirt, grime and bugs without scratching the surface, as long as a suitable cloth is used.

Wax On, Wax Off

Unless you’re a dedicated martial arts student you will probably not wax the acres of aircraft surface area by hand, but rather use some form of orbital buffer to polish the aircraft finish. Most people are aware that a high-speed, straight-spinning buffer can “burn” the surface and leave ugly swirls in the surface. Relatively soft aircraft paint surfaces are far more susceptible to such damage than cars. A low-speed, orbital buffer eliminates that liability.

Finally, after the job is complete, conduct a thorough walkaround, removing all protective tape and masking materials that might have been installed. Depending on how many hours and skinned knuckles it took to complete the job, one might claim an increase of a few knots. Maybe not, but at least a clean airplane looks faster.

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