Maintenance Tip: Things to Ponder When Considering a New Paint Job

Maintenance Tip: Things to Ponder When Considering a New Paint Job

Maintenance Tip: Things to Ponder When Considering a New Paint Job

Thinking of having your King Air painted? No doubt the first thing that comes to mind is the cost. New paint is pricey, and you’ll want to shop around. For a 90 series King Air you could see quotes ranging from $25,000 to $50,000, or more. With bigger aircraft and custom paint schemes, it only goes up from there.

Before you start salivating over paint colors and design, you need to get down to the nitty-gritty. Get several quotes, which may vary immensely in price and what it covers. You’re going to have to dig into the quotes to get an apples-to-apples comparison.

Comparing Quotes

First off, determine what exactly is being stripped and painted. Are they painting the gear? What about the wheel wells and flap wells? Do they pressure wash and paint over certain areas or do they strip and paint everything? You need to know.

How much time do they allow for a basic paint job on your type of aircraft? Does the quote detail the preparation steps and materials used? You don’t want a shop that cuts corners, and you don’t want to be taken to the cleaners.

I’ve seen a lot of King Airs in my day – some with great paint, others not so much. Below, are a few topics for you to keep in mind regarding a new paint job.

Stripping

A King Air will always be stripped before repainting. This can be done with media blast (such as glass beads or walnut shell particles), chemical strippers, or in certain circumstances, sanding. Chemical strippers are the most common choice.

Careful masking of everything not being stripped and painted is just one of the time-consuming parts of the job. Chemical strippers destroy plastic and rubber. Windows, light lenses, beacons, boots, seals and tires will be ruined if they come in contact with stripper. Antennas have a protective coating that is destroyed by strippers. All these items must be well protected.

During the paint stripping process (top) and after all the paint has been stripped off (bottom).

Chemical strippers are highly corrosive, so they must be cleaned off after they’ve done their job. Close attention must be paid to getting stripper out of every crack and crevice where it may have seeped, such as skin laps and inspection panels.

I recently heard about a B200 with a lot of problems following the installation of a G-1000 panel. They double-checked and triple-checked everything to no avail. A great deal of time was spent chasing the problems. Ultimately, they found corroded skin under the antennas, and guess what? That airplane had been recently painted. Apparently, stripper seeped into the antenna bases and compromised their bond. Careful masking should have prevented this.

Prepping the areas on the aluminum skin that were less than perfect, by adding filler and then smoothing it out by sanding.

Prep and Prime

After stripping and cleaning, bare aluminum needs protection against corrosion. For decades, zinc chromate primer, that ubiquitous yellow-green coating found on the innards of every airplane, was the way to go. When chromates were deemed a health hazard, zinc phosphate became popular. It looks exactly like zinc chromate, so all of us old-timers keep referring to it as that. Alodining is another anti-corrosion option. Some shops offer alodining as a “pre-treatment” before the primer.

The world of aircraft paint systems has advanced dramatically from the old days of zinc chromate. Now there are pre-treatments, multi-step primer systems, adhesion enhancers, etc., and we haven’t even discussed paint yet.

Surface preparation is a crucial aspect of any paint job – aircraft painting is certainly no exception. Before or during priming, minor dents or skin distortions are smoothed out with filler and sanded. Although power sanders are often employed, I’m a stickler for sanding by hand whenever possible. The use of power sanders on an airplane make me cringe.

The aircraft after it has been primed and ready for the paint process.

I’ll never forget the King Air that came to my shop for a routine phase inspection. As the owner pointed out his new N-number, I happened to notice some button-head rivets missing. I looked a little closer and saw that every rivet in the N-number area was shorn down flush with the skin! Apparently, the shop that performed the work used a power sander when they shouldn’t have. Needless to say, it was an expensive squawk to remedy. Every rivet had to be replaced and each button-head meticulously re-touched with paint. King Airs are loaded with button-head rivets.

Control Surfaces and Flaps

The ailerons, elevators and rudder are removed and painted separately. They are re-balanced in accordance with the maintenance manual, then reinstalled on the aircraft. Failure to balance a control surface per the manual can result in flutter during flight. If the flutter is extreme, the whole thing can rip off.

Applying the base coat is nearly complete; Matterhorn White is a frequent choice. The wing lockers, cowlings, panels and grates are removed and painted separately.
The layout of a design is underway. The rudder has been re-attached to achieve continuity in the arcing stripe on the tail.

Flaps are another story. Some paint shops remove them, others do not. I feel strongly that flaps should be removed for paint. When they are left on the wing, stripper can seep into areas that are impossible to clean. Where stripper sits, corrosion develops. In this case, the flap bearings and washers are at risk; and when they go bad, the flap tracks are the next to go. Flap tracks are nothing to mess with. If I had a King Air being painted, I’d insist the flaps be removed.

Post-paint Inspection

Don’t be in a hurry to pick up your King Air from the paint shop. Take at least a half-day to look closely at everything. Check for drips, fish eye, gaps and overspray. Minor blemishes and flaws can be remedied, but hopefully there are no such issues. If possible, bring your mechanic along to verify the control surfaces have been balanced per the manual. It behooves you to have someone double check their figures.

Years ago, one of my customers was picking up his C90 after a new paint job. He got into the cockpit and noticed that both airspeeds were stuck at around 80 knots. He checked the pitot tubes and they looked fine – they weren’t covered or blocked in any way. So he gave me a call and we hatched a plan.

The next day, he flew to my shop in another aircraft. I grabbed a spare airspeed indicator, and together, we flew to the paint facility. I installed my spare airspeed on one side and did a quick static pitot test to verify everything was good. The goal was to get this King Air to my shop to fix the other side. As I chatted with the paint shop staff, I discovered they used a blow gun to remove the dust. It seems their guy blew directly into the pitot tubes; that explained the airspeeds.

Extensive masking is required to apply a color over the base coat. The rudder is still on, but will be removed later, balanced per the maintenance manual and reinstalled before the aircraft is delivered to the customer.

Then I began to wonder about other things. I asked to see what maintenance manual they used for control surface balancing. They showed me an F90 manual. Needless to say, this C90 did not leave the paint shop that day. They had to pull all the control surfaces back off, balance them per the C90 manual, and reinstall them yet again. Eventually we got it over to my shop, had the airspeeds repaired, and all was well.

Applying one of the colors. Each time a different color is applied, all else must be masked off.

Fortunately, the owner of the paint shop took this one on the chin. He used this incident as a learning lesson for all his guys and ultimately took his business to the next level. In the years following, he called me many times with King Air questions and I was happy to help.

Level the Playing Field

Most paint shops will give you a generic quote. But, as you can see, it is vital that you delve into these quotes to flush out their differences. You’re trying to get them all on the same page, for a true apples-to-apples comparison. Once you start adding design features (colors, stripes, ribbons, fades, custom logos, and more), sticker shock will soon set in!

Screws – Pay Now or Pay Later

With new paint, there’s one more thing to consider – your screws. What happens to your gorgeous, pristine “virgin” paint job at the next phase inspection? Mechanics with pointed tools open up access panels for inspection and repair. There are many, many panels and each one takes anywhere from six to 20 screws. That’s a lot of screws, and every one of those screws has been painted over.

Your new, fresh paint job has essentially sealed every screw in place. As these screws are removed for the first time since being painted, the paint around the screw head twists, tears and chips away. The thicker the paint, the bigger the problem. I’ve seen paint so thick I could barely make out the screwdriver slots.

It’s a heartbreaking situation for the maintenance shop. There is only so much one can do to minimize the damage. Paint cutters are a good start. Tool sets are available to cut the paint around various sized screws. It’s very time consuming, and it’s not included in the flat-rate for the phase inspection, but it’s much better than taking no action at all. Cutting the paint around every screw is the “pay later” option.

You can avoid this situation altogether by planning ahead before you paint the airplane. These are the “pay now” options. One is to have the paint shop back out every screw a couple turns before painting the aircraft. After the paint has cured, the screws are screwed all the way in. The paint around the screw heads won’t chip when the screw is removed for maintenance, and it’s a much cleaner look than a paint cutter could provide.

The other option is to have the paint shop install stainless steel screws after paint. The advantages to stainless hardware are many: Nothing is painted over; paint around the screws does not chip; there’s no paint to chip off the screw head itself; and the screw head will never rust. This is my preference. Plus, I like the finished look of stainless hardware.

Many designers prefer painted screw heads for the smooth and seamless look. They feel this showcases their design to its maximum potential. But the designer isn’t around after five, 10 or 15 years to see what the painted hardware looks like after the wear and tear of required maintenance. It’s something to consider carefully.

Stainless steel screws have one minor downside. They must be treated properly. You cannot use a power screw driver and run these screws in with one shot. A stainless screw gets hot very rapidly, so if screwed in too quickly, it will gall in its receptacle. This is easily avoided by running the screw in with several short bursts. Otherwise you have the laborious task of drilling out the screw, and tapping or replacing the receptacle. Good mechanics know how to deal with stainless steel screws.

A paint job near the finish line, and a King Air that looks new again.

It’s a Big Job

Painting an airplane is very labor-intensive. It’s hard to imagine the scope of work involved until you see it first-hand. The photos in this article were taken of a variety of King Air paint jobs, and should illustrate the complexity of painting a cabin class aircraft.

Colorful paint schemes and clever designs may fall into the realm of decoration, but every step of a paint job, up through the base coat, is really required protection for the aluminum skin of your aircraft. When it’s time to re-paint your King Air, choose wisely and allow time.

All photos courtesy of Master Aircraft Services in Wickenburg, Arizona. For more information visit www.masteraircraftservicesinc.com or call Gus Haussler at (928) 684-4926.

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