As an authorized inspector I see a lot of neglected aircraft. Many suffer from corrosion and other damage associated with not keeping the aircraft clean or using improper chemicals and cleaning materials. An aircraft’s exterior needs regular and proper cleaning—and the engine, interior, windows and upholstery all need to be kept clean as well.
Planning and preparation
While it may not seem to be a big deal to clean an aircraft, there really is more to it than going out, washing the plane, rinsing it off, and considering it done. While the basic measure is simple enough, it’s the planning and preparation that are important.
As a military aircraft maintenance technician I was involved in maintaining aircraft. The maintenance-plan aircraft were subject to a regular schedule for washing; a freshwater rinse after flying over saltwater; with a turbine engine wash and preservation program to follow. There were work cards and checklists for each task and specific procedures to observe.
Certainly a similar procedure may seem to be overkill for washing a small plane. But no matter the cost or size of the aircraft, a systematic approach to cleaning it will protect your investment and aid in proper maintenance.
In addition to protecting your investment there is also the important issue of protecting the environment. Many airports now have specific areas for washing aircraft that are designed to collect wash water and associated materials so that this tainted water does not get into the ground, lakes or streams before being properly treated.
Personal preparation, to include safety equipment and appropriate clothing, should also be on the top of the list when you’re preparing to wash your aircraft. Adhere to any precautions on the labels of the cleaning materials you intend to use, and always use protective gear such as goggles or masks and gloves. Wear shoes that will reduce the chances of slipping or falling on wet, slippery surfaces.
Prepare the aircraft, as well. There are many areas of an aircraft that should not come in contract with wash water. Take the time to prevent wash water from entering sensitive areas such as avionic cooling ducts, pitot and static system ports, heater air inlets, fuel vents and caps, landing gear and carburetor air intake ducts. All of these areas should be blocked with some type of barrier material so water won’t enter.
I advise the use of surveyor’s tape (flagging tape) in a high-visibility color to mark the areas that must be cleared after washing. You might even want to get fancy and record and number each streamer so that you can inventory the streamers once you are done to ensure you have removed them all. More than one aircraft has been destroyed by attempting flight with a blocked static or pitot port or with a fuel vent obstructed.
Never use clear tape directly over pitot tubes or static ports; it’s difficult to see, especially in low light. I recommend using a heavy-duty trash bag to cover the landing gear, wheels, brakes and hydraulic actuators to prevent water from entering these areas.
Do not use any type of tape with adhesive directly on aircraft components as the residue left behind will attract dirt and dust, accelerating wear in important areas such as landing gear.
Use some type of cowl plugs for the engine. Don’t spray water into the engine area, as it will do nothing but cause problems—and water alone won’t clean the engine without the addition of special materials (e.g., mineral spirits) to remove grease and oil.
When washing an aircraft the optimum outside air temperature should be between 50 and 80 degrees F, with the plane preferably not in direct sunlight.
Start washing from the front to the back in the same direction as the normal airflow in flight (or top to bottom, as a secondary method). This will help to prevent water from entering areas that should not be subjected to excessive moisture. Aircraft have autopilot servos, electrical connections, sensors, antenna connectors, flight control cables, jack screws and other items that don’t do well with an excessively moist environment.
Cleaning materials
Aircraft are primarily made of aluminum; however, some aircraft are now made of composite materials, or have many parts made out of composite materials that you may not be aware of. Whatever your plane is made out of, washing it requires the use of approved chemicals, soaps and cleaners.
Aircraft maintenance and owner’s manuals may list approved materials and methods for cleaning. Most if not all aircraft cleaners have either a military specification (MIL-SPEC) number or some statement on the label indicating that it is approved by an aircraft manufacturer for aircraft use.
It’s unfortunate, but grocery and hardware stores don’t usually sell cleaners that are appropriate for use on aircraft. Aircraft supply houses are good sources for aircraft cleaning materials; most have all types of cleaners that work wonders on all the parts of an aircraft and are aircraft-safe.
Corrosion is always an issue with aircraft made of metal but an additional problem exists with certain chemicals and aluminum and parts such as landing gear fittings, engine mounts and wing spar attachments. All of these highly stressed parts, when allowed to make contact with adverse chemicals, can cause hydrogen embrittlement and failure of critical parts.
Airplanes are expensive but they can be replaced. However, human lives could be jeopardized by the use of unapproved or inappropriate cleaning materials. Certainly no one wants to intentionally cause an accident; therefore, it’s necessary to educate yourself about proper materials to use when cleaning.
Corrosion can start small and work its way up to being a major issue, ultimately causing structural failure. I have seen aircraft where the aluminum skin was so consumed by corrosion that I could push my finger through it.
Alkaline-based cleaning compounds are not to be used on aluminum aircraft. Household soaps that people have used for decades may have worked okay in the past, but times have changed—and many of the old formulas for soap and cleaners have changed, too, and may not now be okay to use on aircraft.
Don’t take a chance. Spend the money and get the right product.
Where and what to clean
Problem areas that require attention include the belly of the aircraft or behind the engines (in multi-engine planes). These areas accumulate oil, grease and hydraulic fluid which attract dirt, trap moisture and cause corrosion. There are several good cleaners on the market for this job, including Extreme Simple Green Aircraft & Precision Cleaner. (Household-variety Simple Green does not have the same formulation, and could harm your aircraft.)
The use of a mechanic’s creeper, goggles, gloves, several soft cloth rags and some elbow grease will make cleaning a dirty belly relatively easy. Once the grease is cut and the surfaces cleaned and rinsed well, it will be much easier to keep clean on a regular basis, particularly if the area has also received a good coating of wax.
Check for moisture at the drain holes typically found in the lower aft corners of the fuselage formers, wings and flight controls. These areas must have unobstructed drain holes to allow moisture to exit the aircraft. If they are plugged up or clogged with dirt and grime, the obstruction must be removed.
Do not use water to try to force the debris out; the use of a nonmetallic brush with a vacuum will work wonders in these areas. (This is best done during annual inspection or whenever the aircraft is opened up for access.) It’s not moisture alone that causes corrosion—it’s the contaminants (dirt, oil, exhaust residue) combined with the water that cause damage.
Trapped water anywhere can be a serious safety issue. I was once treated to the challenge of flying a single engine tailwheel aircraft with more than a gallon of water trapped in an aft section after a heavy rainstorm. I was fortunate that the aircraft was not heavily loaded to the aft, or I doubt that the aircraft would have been controllable due to a severe aft CG problem.
Tires are another item that must be kept clean, but certain actions can damage the rubber.. Do not use automotive tire treatments on aircraft tires as aircraft tires are not made of the same material as automotive tires. (For more information about tire care, see “The Rate of Inflation” by Tim Kern on page XX of this issue. —Ed.)
Battery boxes must also be kept clean, and the vent and drains kept clear to prevent acid from spilling onto the aluminum structure. Aircraft electrical systems should be checked at least on an annual basis for proper voltage regulation and adjusted as necessary to prevent overcharging of the battery and excess venting of electrolyte, which is also corrosive.
Aircraft windows are typically made of acrylic plastic, not glass. Do not use glass cleaning products on plastic windows (especially products that contain ammonia), use a product made for cleaning aircraft windows and a clean, soft, dirt- and dust-free cloth. (Great Lakes Aero Products, a PFA supporter, sells scratch removal kits. See Resources for contact information. —Ed.)
Old but clean cotton T-shirts work well for cleaning windows; however, don’t use dryer sheets with these T-shirts as it can create an electrical charge on the shirts which will attract dust.
Never use paper of any kind on plastic windows—this includes paper towels or other material made from paper products—or you may scratch the surface.
Aircraft interiors also must be kept clean and free from moisture Any accidental sources of moisture in the interior, no matter how small, must be cleaned up as soon as it’s practical. Whether it’s a spilled drink or a leaking sick sack, moisture can cause corrosion to form in a short amount of time.
If your aircraft has a few leaks when left out in the rain, invest in a good quality cover to prevent moisture from entering your aircraft. An excessively humid environment in the aircraft cabin can cause electrical and avionics malfunctions that can be difficult to trace and correct.
Check all window and door seals on an annual basis (at minimum) and replace door and window seals as necessary to prevent water intrusion. Any time moisture is allowed to remain on aluminum or copper wiring and connections for any length of time, corrosion will begin and spread rapidly. This is especially true for unpainted aluminum.
Operational considerations
What you do before, during and after a flight as pilot in command can have a major impact on the cost of operating an aircraft. Keeping an aircraft clean is part of good aircraft maintenance.
Sometimes it’s attention to the minor details that can save some serious money over time. For example, do you wipe your shoes off before entering your aircraft? When you place your feet on the rudder pedals, dirt that falls off your shoes can make its way down onto the brake cylinders.
Eventually the dirt and other contaminants work their way into the brake cylinders, causing the seals to leak hydraulic fluid and requiring maintenance to reseal the brake cylinders and purge the hydraulic system of contaminants.
As an aircraft owner consider what may be done to prevent an aircraft from becoming excessively dirty in a short time. Whenever possible, select a parking area some distance from a runup pad or frequently used taxiway. Parking into the prevailing wind is much better than other positions that may allow moisture to enter areas of the aircraft that are not designed to accept it.
Should you invest in a cover for your aircraft? Yes, by all means invest in a cover as the benefits far outweigh the cost.
Should you fill up the oil sump to capacity or run it a few quarts low to keep oil off the belly of the plane? Some aircraft engines operate efficiently at an oil level less than the maximum capacity, but others have a limited capacity oil sump and need to operate at close to the maximum oil level. Check the POH for your aircraft, and ask owners of similar aircraft what they experience.
If you have an oily belly after only a few hours of flight then it is possible that there is a problem with the engine, and maintenance may be required. The fact that oil is being deposited on the belly of the plane could be the result of something as simple as the incorrect routing of the engine oil breather/vent line; a slight vacuum at the outlet is all that is needed to draw oil mist out of the breather, creating an ugly mess.
The same goes for excessive exhaust residue on the underside of the plane. Use the proper fuel/air mixture for conditions and if you have a problem with exhaust residue, check that the exhaust system is the original configuration. Unapproved modifications to the exhaust system, including the tailpipe, can cause many problems.
In-flight operations can have a significant impact on the cleanliness of your aircraft—as can proper disposal of any waste generated while in the air. Stow any trash, including sick sacks or pilot/passenger relief bags, until you are on the ground. After a flight it is important to spend a few minutes cleaning up the bug splatters (insects’ remains are corrosive); wiping off the excess oil and exhaust residue; and spending the time to do some general housekeeping. Invest in a cleaning kit for your aircraft with items such as aviation-approved cleaner(s), an ample supply of clean cloth rags, maybe a portable vacuum, plastic window cleaner and a trash bag or two.
Final thoughts
A clean aircraft shows pride of ownership and represents your attitude about flying, proper maintenance and protecting your investment. The use of the proper materials and procedures will keep your aircraft looking like new for years.
Michael Berry, a former aircraft repair shop owner, is a multi-engine rated ATP (757/727). In addition, he’s a turbo jet flight engineer, an A&P/IA mechanic, airplane owner and 121 air carrier captain. Berry has 15,000-plus pilot hours. Send questions or comments to editor@www.piperflyer.com.
RESOURCES
Great Lakes Aero Products, Inc.
glapinc.com
