How to Paint An Airplane
Painting an Airplane can seem like a challenging task. After all the finish is critical for a variety of factors. In contrast to painting cars, airplanes require special consideration of the coatings weight and the coatings properties. If the coating is applied to heavily, it could have negative consequences on the planes flight performance. If the coating is not applied to the correct amount or properly selected, it will not provide the protection it should from the elements. The FAA actually contains a fair number of regulations about painting planes and has a lot of information here. In this article will cover a few key ideas to consider when painting an airplane.
Coating Considerations
Selecting a proper coating is crucial in being able to ensure that the coating has met the right regulations for aviation and will provide the correct performance. Companies that have a presence in Aviation coatings include Sherwin Williams Aerospace Coatings, Akzo Nobel, and PPG Aerospace Coatings. Speaking with them is an important first step in learning about their coating systems and benefits to see which might make sense for you. A few things to think about the coating itself include whether it has a pot life, which will reduce the length of time you can spray before having to replace your material if your not using a plural component system. You will also want to ask about any special application environment requirements, many aerospace coatings have contaminants that require expensive and special spray booths for application. You will also want to make sure to receive the Technical Data Sheets and Material Safety Data Sheets so that you can fully understand the coatings and recommended application methods. Sometimes these coatings are required and will also require an additional expense to install the higher expense equipment along with higher expenses associated with replacing the booth filter. A final recommendation is that you should stay with the same coating supplier for each project to ensure they will be able to support you with any issues that come up with application.
Application Considerations
For coating application equipment there are a few options of equipment categories to choose from and will briefly highlight them here. In addition to categories you can choose between HVLP or Conventional Spray or Air Assist Airless. For an overview of conventional vs HVLP and Air Assist Airless check out this article.
Pressure Fed Spray Guns – These will provide the greatest control over the spray process and allow for longer painting times. They also offer the second greatest production of the 4 options discussed. The challenge is that you will have two hoses with you at all times. Pressure Fed Spray Guns will be a higher cost than a plane gravity or suction fed spray gun due to needing a pressure tank to feed the spray gun material, they are not as expensive as Air Assist Airless Spray Guns.
Gravity Fed Spray Guns – gravity fed spray guns will not hold as much coating as a pressure fed spray gun and will require materials that flow naturally (which means they need to be lower viscosity). They are more portable than a pressure fed spray system though.
Suction Fed Spray Guns – Suction Fed Spray Guns are similar to gravity fed spray guns that they will work well with thinner coatings are more portable.
Air Assist airless Spray Guns – Air Assist Airless Spray Guns provide the highest production of the methods mentioned and can often achieve a finish quality similar to HVLP Spray Guns. They are the most expensive of all the methods mentioned and typically would make sense only if you are using a relatively large volume of paint at a time. This is because they require a lot of solvents to flush their lines and if you are not using a heavy amount of fluid at a time. However, if you want higher production air assist airless can be a good fit as it will have a high transfer efficiency with the highest amount of production.
For Most Aircraft Coatings a HVLP style spray gun will be ideal or an Air Assist Airless Spray Gun for larger production. The style of fluid delivery will depend on the size of the aircraft and whether you are painting parts or leaving the plane in tact.
Filling in of low spots
For a composite plane you will need to fill in low spots on the plane. This can be a time consuming process but for a good review of the process you can check out this article.
Cleaning Old Paint from the Plane
Removing old paint from the plane can be done in a variety of ways. Will highlight the most common ways below.
Chemical Stripping
Paint can be removed from a plane using chemicals such as EFS-2500 which is a great option as it will remove both the top coat and primer off simultaneously. For other ideas you would want to work with your coatings representative
Plastic Beads or Corn Starch Sandblasting
Paint can also be removed using delicate sandblast medias like Corn Starch and plastic beads. A reputable sandblast company should be able to help in determining the ideal media for your removal needs and have a lab that will ask for a product sample and your desired profile. They will then help to determine the media type, pressure setting, and blast times to achieve the profile. The benefit to using plastic beads or corn starch is you do not have to deal with significant harmful chemicals.
Sanding
Sanding is most often used when a spot repair is needed on a part of the plane or if you want can be done on larger surfaces as well. A good overview of the sanding process can be seen here.
No Matter how the surface is prepped you will want to verify it has been done to a deep enough profile and done to the coating manufacturers Specification. This will ensure proper bonding of your coating.
Air Supply Considerations
You should speak with your coatings representative to know about your coatings to know if special air supply will be required for your painter. A lot of times Aircraft paints have Isocyanates which are harmful, odorless, tasteless, chemicals that can be found in paint. If your coating has isocyanates you will definitely want to consider a forced fed paint respirator. The coating representative may recommend a forced fed air representative for other reasons, and if you have any questions or want extra assurance you can check with OSHA for free consultation. You will also need a forced fed respirator with your blast equipment.
Application Technique
For an overview of how to use a pressure pot you can view this tutorial. Or for a gravity fed spray gun check out this training. One recommendation would be if possible to paint the plane in pieces. This will help reduce the potential for finish quality issues like dry spray or runs from ruining the entire finish. If an issue occurs in an isolated part you can clean the effected part without having to clean the entire plane. If you need to do a spot repair you can expect to need to clean about 3 times the area of the repair.
Safety Considerations
Fire Safety – For a general overview of painting applications fire requirements you can check out NFPA 33 which guides fire restrictions for spray applications but ultimately your local authority will have the final say. For another good overview of considerations about fire safety you can consult Global Finishing Solutions. Ultimately it is recommended to use a spray booth to meet all code challenges for spray application. Additionally, you will want to check with the EPA about rules of paint stripping and coatings for your area andOSHA as well as county resources to ensure you are properly meeting all health and environmental considerations.
Photo by tharty (Flickr: sea air plane) [CC BY 2.0], via Wikimedia Commons
