A palette for your plane

 - March 19, 2008, 5:52 AM

There are those unsung workers whose skills are underrated and whose work may go unappreciated, or at best is taken for granted. So it is with those who paint business airplanes. It’s a sometimes nasty, often physically demanding, always labor-intensive job that requires a knowledge of chemistry and the soul of an artist.

To the uninitiated, which is just about anybody who doesn’t paint airplanes, it seems a relatively simple process. The truth is, there is nothing simple about it, from the moment the owner sits down with the designer to long after the airplane is rolled out of the paint bay and delivered.

The tendency, according to those in the business, is to think of aircraft paint in terms of cosmetic appearance or marketing potential, or both. Paint does more than make a statement about the owner, the company or the product.

“The original idea of paint was to protect the skin of the airplane,” said John Murphy, manager of modifications at Midcoast Aviation at St. Louis Downtown Airport. “That hasn’t changed,” he noted, “but at the same time it has evolved into an important visual element of the airplane. It has to have a high-dollar, showroom shine. Even when it’s sitting still, it has to look like its going 500 knots.”

From the paint shop’s perspective, it is both a visual statement and the protective shell on a multi-million-dollar investment. And there is a lot more to the job than picking up a spray gun at the local home-improvement store and spritzing on a coat of paint.

It starts with the design. That’s the part, said one designer, where “the client tells us what he wants, we tell him what’s actually possible and hopefully we meet somewhere in the middle.” The middle, he admitted, is a moving target.

There are clients who absolutely want what they want. One owner insisted that he wanted his business jet painted black. And so the paint shop, after much tactful counsel against it, relented and did exactly what the customer wanted. Less than a month later, the airplane was being scheduled back in the paint shop to be stripped and repainted– white–at the owner’s expense.

White and various tones of off-white remain the most popular. But the traditional one- or two-colored pinstripes stretching from the nose to the tail are giving way to more creative ways to accent and personalize the airplane. Stripes may be of three or four different colors, and expand and curve into a spray of curls. A few bold individuals are opting to have the accents on the aircraft applied in a relatively new paint that reflects color differently as the viewing angle shifts. It is most dramatic on a moving aircraft. As the viewing angle changes, the colors shift and change and even appear to move.

Since 9/11, Chad Doyle, president of Jim Miller Aircraft Painting in Uvalde, Texas, said his shop has had fewer requests by security-conscious owners for company logos. But at the same time, he noted, “We’re putting a lot of American flags on the tails.”

The High-solids Revolution
For a long time, paint was paint. Little changed from one year to the next. Regardless of brand, it consisted of about two-thirds volatile organic compounds (VOCs) that thinned the paint to a viscosity that made it flow easily through a paint gun and dry quickly. The other one-third was color pigment and a binding agent, referred to as the “solids.” The proportions remained standard, and solvents from one manufacturer worked well with the pigment and binder of another. Paint shops knew the properties of conventional paints well and became comfortable with their use. Then came high-solids paint (HSP).

In a world increasingly filled with environmental concerns, government agencies demanded a reduction in the release into the air of VOCs. High-solids paint was, in fact, created in direct response to federal requirements set by the Environmental Protection Agency’s national emission standards for hazardous air pollutants. It was immediately embraced by the industry.

In HSPs, fully two-thirds of the volume is pigment and binder solids and only one-third VOCs. Although more difficult to apply, this mixture places less VOC-laden overspray in the air to be filtered and disposed of later.

But while high-solids paint may have solved environmental concerns, it brought new challenges. Unlike conventional paint, the VOCs from one manufacturer may not be used with the pigment/binder of another manufacturer. And its heavy viscosity makes it more difficult to apply and requires greater skill on the part of the painter to achieve the high-gloss finish that customers expect.

Doyle said his company is “still pretty much shooting conventional paint.” The reason, he said, was simple: “We just get a better finish.”

Doyle explained that when mixed as recommended by the manufacturers, the relatively dense mixture cannot be as finely atomized as conventional paint. And if the amount of VOCs is increased to more finely atomize the paint for a smoother finish, “you’re releasing the same amount of VOCs that you would if you used conventional paint.”

Nevertheless, paint shop managers seem to agree that high-solids paint is here to stay, and most paint shops have learned to work with it to their own satisfaction and, apparently, to the satisfaction of their customers.

Metallics and Color Shifts
While metallic-finish paint may create a striking visual effect, paint shop supervisors agree that it is difficult, if not impossible, to apply in a smooth, even finish. The paint pots require constant agitation to stop the metallic glitter from settling, and differences in the thickness of the paint may change the appearance. Later, it becomes virtually impossible to match the original paint, whether it is a small touchup or painting of a replacement hatch.

Ed Kirby, the paint shop manager at Bizjet International in Tulsa, Okla., is no fan of the metallics. “You can never get metallic paint from two different manufacturer batches to match. And it’s almost impossible to get an even finish from one end of the airplane to the other, even with all the paint from the same batch.

“I’ve painted two airplanes in silver metallic,” said Kirby, “and I’d never do it again.”
“If they want it, we can do it,” said Midcoast’s Murphy. But he noted that it is not only more expensive–about 5 percent more than conventional paint–but for it to shine a final clear-coat is required, and in some cases the addition of metallic glitter to the clear coat as well.

As for the so-called “flip flop” paint that changes color as the viewing angle is changed, it is more commonly known by its trade names. Manufacturer Du Pont calls its product Chromalusion. The House of Color in Picayune, Miss., calls its paint Kameleon Kolors. Both are unique in that, upon drying, the colors change as the angle at which it is viewed changes. Paint shop managers seem to agree that it is an interesting product, but only for striping, logos and other accents because it is very thin and several coats are required, followed by a clear coat.

Price is also a major consideration. A 2.5-gallon kit of conventional paint (solvent, pigment and binders) costs about $250 for the off-whites to $350 for reds and metallic-finish paint kits. Depending on how many colors the customer wants in Chromalusion or Kameleon, the cost may approach $1,000 for a one-pint kit. This would put the price of paint alone for a Citation V at about $25,000, pushing the total cost to somewhere in the $55,000 range, compared with a $30,000 price tag for a conventional paint job.

A Job Well Begun Is a Job Well Finished
While a choice of paint is critical, it is certainly no less important than the process of preparing the airplane for painting.

From the time an airplane is rolled into a strip-and-prep bay to be repainted, it will go through nearly a dozen steps before the first coat of base paint is applied.

Sensitive areas such as windows and pitot tubes must be covered in aluminum foil paper and masked off with foil tape. The stripper is applied, followed by a thorough seam cleaning and remasking where necessary. In fact, the strip-and-prep phase requires far more manhours than the actual application of the final base coats of paint.

The equipment is as important as the paint used, starting with the paint shop itself. The shop hangars vary in size, with relatively few capable of accommodating aircraft as large as a Boeing 747.

The paint bay is a key to controlling temperature, humidity and air movement, factors that can affect the application and finish.

The isocyanates present in modern paints are there as a curing agent and react with resins to produce what is commonly known as polyurethane and its characteristic “wet look” finish. But these isocyanates break down in air that contains too much moisture, and the result is a flat or hazy finish referred to by painters as “blush.” This may also happen if the humidity is allowed to rise before the applied paint is sufficiently dried, or “cured” as painters described the process.

A higher temperature, assuming a constant humidity level, means the paint will dry more quickly. Perhaps even too quickly, which can result in “flash over” drying, creating a skin of dried paint under which the remaining paint is continuing to dry. As this occurs, the gases emitted force their way up through the skin in the form of thousands of tiny pinholes, or what the painters refer to as “solvent pop” or “orange peel finish.” This may also occur if the initial base coat is not allowed to dry sufficiently before the second base coat is applied.

Most paint shops avoid this by adjusting the amount of additives in the paint. But ideally the temperature in a paint bay should range from 75- to 80 degrees F, with a humidity level of about 40 percent.

The new paint shop being built at Dassault’s Little Rock, Ark. facility will feature both humidity and temperature control, which paint department manager Alan Tompkins said will ensure optimum painting conditions, even on days when the outside temperatures in a muggy Arkansas summer climb well over 100 degrees F and the humidity rises past the 70-percent mark. It will also permit a rapid increase in temperature to about 120 degrees F to reduce the time required for the pre-delivery curing of the paint. The new shop will have two paint bays and a dedicated strip-and-prep bay, and Tompkins said he is looking forward to the downdraft system to exhaust and trap the overspray and VOCs.

Sucking Up the Bad Stuff
“It seems everybody likes the downdraft system; it makes for a more uniform flow of air and exhausts the overspray more quickly,” said Tompkins.

Most existing paint bays employ either a crossdraft or updraft. The updraft, like the downdraft, incorporates a “tacky” filter system for trapping overspray and VOCs. The crossdraft typically uses a waterfall in which overspray and VOCs are caught and drained into a treatment system. The hazardous waste is removed to be sent to an approved disposal center and the remaining water is diverted into the sewer system.

The “tacky” filters for downdraft or crossdraft are surprisingly expensive. At Midcoast Aviation, both paint bays use the crossdraft system and each has a three-stage tacky filter process. According to Britt Julius, paint shop supervisor at Midcoast Aviation, the cost of replacing all three filters in a single bay over a year is in excess of $12,000.

Paint shops must meet EPA standards, no matter what system is used, and many states and municipalities have issued guidelines far more strict than those of the EPA.

These regulations, claim paint shop managers, are a major challenge. Doyle pointed out that not only does Jim Miller Aircraft Painting meet the EPA standards, it also remains within environmental guidelines set by the state of Texas and by the municipal governments of the Dallas/Fort Worth area. “After the first two or three high-ozone days,” said Doyle, “the local regulations kick in and the amount of VOCs that can be released is less.”

The environment regulations also result in mounds of paperwork. “We have to document the time we starting emitting VOCs, how long we sprayed and how much we sprayed in an hour,” said Doyle. “I have one guy whose only job is to document this process.”

For conventional paint or high-solids paint, the “weapon of choice” for paint shops seems to be the high-volume, low-pressure spray gun. And there appears to be a preference for the electrostatic spray gun that has made painting far more efficient. The technique is similar to that of rubbing an inflated balloon on a fuzzy wool sweater and then sticking the balloon to the wall. The aircraft is grounded, giving it a negative charge, while the sprayer emits paint that has a positive charge. The result is a spray that is drawn to the surface, where it sticks more securely.

Good Paint Requires Good Skills
Good painters are born, not made. Paint shop supervisors will not go quite that far in describing the men and women who actually apply paint to the aircraft, but as one supervisor put it, “They’re worth every penny we pay them.”

The painters are the people who struggle into special suits and masks to protect themselves from overspray and toxic VOCs and spend anywhere from four to six hours dragging a heavy spray gun around an airplane to shoot a couple of coats of paint. It’s a hot, exhausting job.

“He’s part monkey, climbing across scaffolding three stories high, lugging a two-pound paint gun and a garden hose trailing behind it, wearing a hood with air being pumped into it and putting on the perfect coat of paint,” said Dassault’s Tompkins.

“I can tell you in 20 minutes if someone is going to be a sprayer,” said Kirby. “It’s a particular talent, and you have it or you don’t. And if he has the talent, then he has to learn the techniques; how to handle the gun, how to position himself and his equipment.”

“We have five guys painting. They know one another and they know their jobs. When [the paint] comes out nice, it was a symphony. When it doesn’t, somebody wasn’t playing from the same score as the others,” explained Tompkins. “Of the 53 people in the paint shop, I have about 13 who are top-notch painters, and they all share two common characteristics–aptitude and attitude.”

“You can give some people one attempt after another, and they never get the hang of it,” said Midcoast’s Murphy. “It’s both a skill and an art, and without a doubt they’re worth what we pay them.”

Midcoast uses a team of six to paint an aircraft, four of them painters and two assistants. Most have been together at least three years. “We have everybody dancing together, spraying the same mixture, at the same pressure, from the same spray guns, from the same pressure pot,” said Murphy.

Bizjet International also uses teams who have experience working together. “We have one guy who paints forward of the engines and one guy who paints aft of the engines, and another guy who does nothing but the underside of the wings. From start to finish, they’re working five hours on a Falcon 50 to put on three coats of paint.”

At most paint shops, the painters are trained to apply paint in coats five to seven millimeters thick. An even greater challenge is applying paint around the RVSM-compliant pitot-static sensors. In these areas, the FAA requires that the paint thickness be within very exacting limits for any particular aircraft or group of aircraft types.

If a stripe or accent passes through the area assigned–given frame areas of perhaps a six-inch radius around a port–any raised edge must be “milled down” to the same thickness as the surrounding paint, with no edge that might distort the airflow across that part of the aircraft skin.

Also a challenge to the painter’s skill is the top of the wings. “If we do ten airplanes,” said Murphy, “we may not like the paint on two of them. It’s an area that anyone sitting in the cabin can see perfectly, and from that angle they can see the entire wing and even the slightest imperfection is obvious.”

Less challenging are the new composite materials that began appearing on aircraft a little more than a decade ago. While most airplanes have at least some composite materials that require paint, others, such as the Raytheon Premier I, are made almost entirely of composites.

Painters generally like applying paint to composite materials. Unlike aluminum, the composite materials readily accept paint, the paint adheres well to the relatively rough surface and it is no more difficult to strip old paint from a composite than it is to remove it from an aluminum surface. In fact, the lack of rivets simplifies removal of the old paint.

On the downside, the chemicals used by the manufacturer to ensure that the composite material is easily removed from the form must be carefully removed, just as any organic substance such as grease or oil must be removed from the aluminum skin. Failure to do so will result in “cratering” and “fisheyes,” round indentations and imperfections in the finish.

Putting On the Glitz
Perhaps no less skilled are the men and women who prepare the aircraft for accent markings. Several years ago, some shops thought the use of laser light as a guide for masking of accent areas would be a good idea. Many quickly discovered that as long as it was a straight line, it worked fine. However, said Tompkins, “The human eye is its equal, and the human eye remains the best tool.”

It is typical for the outline of a particular accent to be applied using fine-line layout tape on one side of the aircraft. The reverse mirror accent outline on the other side is then applied by eye, using various reference points, such as windows, pitot tubes, antenna, and so forth. “There are very few people out there who can do it and do it well,” said Kirby. “I’ve been painting airplanes for 23 years, and I can’t do it that well. If you’ve got a guy who’s good at it, you pay him well.”

What he and others in the paint shop are worth is measured in customer satisfaction when the airplane is delivered. But it is also the point at which anyone who was involved in the job feels much like a parent dropping off a child for the first time at the day-care center. “Please take care of my baby,” they whisper.

Most paint shops do a little more than whisper. They are aware that how long this paint job lasts is going to depend a great deal on how well the owner cares for it. To this end, paint shops advise:

• Avoid flying the airplane through rain for the first 30 days, after which the paint should be cured. Some shops even stretch this rule to the first 90 days.

• Do not wash the airplane for at least the first 30 days, and do not allow water to stand on the airplane, not even dew, as it may stain the paint.

• Do not wax the airplane until after the first year of service.

• To maintain the quality of the paint job, keep it hangared as much as possible, as ultraviolet rays will break down the paint and salt in the air at airports near the ocean can quickly dull the finish and result in corrosion; wash only with warm water and mild detergent solution; use isopropyl alcohol to remove exhaust soot, grease and oils; and repair any chipped paint with the kit supplied, as any chipped area of paint is only going to become a larger chipped area of paint and eventually lead to corrosion.

With care, said Kirby, a good paint job will last at least five years, “and I’ve even seen ten-year-old paint jobs that looked great. But it requires the attention of the maintenance department and professional aircraft detailers.”

Kirby said some owners simply build into the budget a new paint job every three to five years. “But a lot of individuals have discovered that, with care, their airplane is going to keep that new-paint look for a whole lot longer.”

At a cost of about $35,000 to strip and repaint a light jet to $140,000 for a Gulfstream, it would appear to be in the owner’s best interest to take Kirby’s advice to heart.

Sikorsky Develops VOC-free Paint

In a world in which a clean environment is an increasing concern, Sikorsky Aircraft has what it believes is a solution that eliminates the need for harmful volatile organic compounds (VOCs) in aircraft paint.

It is part of what Sikorsky manager of safe and green aircraft programs Bob Araujo said is the Stratford, Conn.-based company’s “fourth era of environmental programs.”

For about four years, Sikorsky has been evaluating what it calls a zero-VOC topcoat that meets mil-spec requirements for “coat, polyurethane, high solids” and the U.S. Navy recently approved the product “for all future Sikorsky helicopter deliveries.”

The VOC-free paint is a joint project of Sikorsky, Deft Coatings of Irvine, Calif. and the Naval Air Warfare Center’s organic coatings team. According to Sikorsky, it is applied using the existing high-volume, low-pressure spray gun, resulting in “a uniform appearance with no anomalies.” It has “virtually no odor, is non-flammable, has an approximate 25-percent reduction in paint usage and weighs approximately three percent less than existing paints.”

The specific VOC-laden solvents eliminated are xylene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK) and toluene. All these materials, said Sikorsky, have been identified by the Environmental Protection Agency and are on the EPA’s list of 17 chemicals targeted for reduction and/or elimination.

Sikorsky did not reveal details of the ingredients in its new VOC-free paint. However, the Connecticut Department of Environmental Protection noted that the partnership with the company was formed to “create and test new formulations of the polyurethane topcoat that would reduce or eliminate organic solvents and still maintain the performance required by their customers.” Polyurethane paints are based on resins made by the condensation of organic isocyanates with compounds or resins containing hydroxyl groups. Industry insiders speculate that the environmentally unfriendly solvents have been replaced by environmentally friendly agents designed to cure the paint through chemical reaction, or that it might be a water-based paint.

It is known that other manufacturers are also working on similar VOC-free coatings–epoxy primers and polyurethane–including PRC-DeSoto, Sherwin-Williams, Spraylat and U.S. Paints. Sikorsky declined to speculate on adaptation of the zero-VOC paint for use in the commercial aviation industry.

Repainting the Business Jet from Prep to Polish

Repainting a business jet is not simply a matter of stripping off the old paint and slapping on a new coat. It is a labor-intensive, exacting process that requires a knowledge of chemistry and the patience and skill of an artisan. The following is the process typically followed by the Dassault Falcon Jet Completion Center paint shop in Little Rock, Ark., for the repainting of an aircraft:

1. Customer and designer reach an agreement with regard to design and concept, colors and so on. If the design is to remain the same, photographs are taken of the original paint scheme and templates made so the new design will exactly duplicate the old one.

2. Portions of the airplane not to be painted are masked off using aluminum foil paper and foil tape.

3. The aircraft is rolled into the strip-and-prep bay, where chemical stripper–a non-corrosive, mild, formic acid–is applied. The aircraft will sit for six to 12 hours while the stripper does its work.

4. The aircraft is thoroughly steam cleaned, after which some masking may be replaced. Areas where chemical stripper cannot be used, such as those made of composite materials, will be sanded at this point.

5. A methylpropeal ketone scrub is applied to ensure removal of any organic film, such as grease.

6. A thorough wash in mild soap and warm water completes the cleaning.

7. Etching solution is applied to prepare the aluminum for painting. The solution also serves as a final cleanser.

8. Cool water is sprayed over the entire aircraft to search for any “water break” indications that an organic film was not removed in the earlier cleaning. If the surface is clean, it will present an even, wet appearance when water is applied. If the surface is contaminated, the water will separate and appear to “bead.”

9. An alodine solution is applied to further promote adhesion of the paint and further inhibit corrosion.

10. The aircraft is allowed to dry completely and the first coat of anti-corrosion primer is applied, less than a millimeter thick, and allowed to cure for four to six hours.

11. Sanding/building primer is applied and allowed to cure for about 24 hours.

12. The entire surface to be painted is sanded using vibrating and orbital sanders. Sensitive areas, such as around the pitot tube, are hand sanded.

13. The airplane is then blown dry and a chemical wipe is used to remove any dust. If necessary, areas not to be painted are remasked.

14. The aircraft is moved into the paint bay to receive the first base coat. This coat is allowed to dry for about 45 minutes, then the second base coat is applied. Following the second coat, the paint is allowed to dry, “cure,” for 12 to 24 hours.

15. Tape and masking for accent stripes, logos, registration numbers, flags and so on are applied, and those areas are painted with the appropriate colors.

16. The airplane is moved to the completion hangar, masking is removed, the job is inspected and any touchup done.

17. The post-paint phase sees the installation of any parts that were removed and painted separately. Unpainted parts, such as door latches and wing leading edges, are polished.

18. The finished airplane is delivered to the customer, along with a touch-up kit and recommended care and maintenance instructions.