Maintenance

Degreasing Landing Gear: All You Need to Know

Keeping an aircraft clean is an important aspect of its maintenance process. According to the FAA, “from an AMT’s viewpoint, it should be considered a regular part of aircraft maintenance.” While cleanliness does enhance the aircraft’s aesthetic appeal and inspires confidence in its quality, its primary importance lies in being the first line of defense against a major threat to the airframe: corrosion.

Implementing a comprehensive cleaning routine is a simple yet effective method to degreasing landing gear. Here’s what the FAA has to say on the matter.

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Causes of Corrosion on Landing Gear Assemblies

Corrosion is the primary threat to any airframe assembly—without question. It’s often considered the most dangerous enemy of an aircraft because while components like engines or environmental systems can be replaced, corrosion spreads like cancer throughout the entire airframe.

In essence, four key elements must be present for corrosion to occur:

Anode: A metal prone to rusting, typically steel in aircraft.
Cathode: A dissimilar metal that’s less likely to corrode, such as aluminum or a protected part of the same metal.
Electrolyte: A conductive liquid that allows ions to move between the anode and cathode—usually water.
Electrical contact: An electrical connection between the anode and cathode.

Environmental Factors Responsible

The previous explanation simplifies the complex nature of corrosion. Aircraft operate in extreme conditions, and various environmental factors significantly impact how quickly corrosion develops. For example, seawater accelerates corrosion up to 1,000 times faster than tap or distilled water. To combat this, the Air Force follows a standard washing schedule, with aircraft near coastal areas being washed six times more frequently than those stationed inland.

Stresses Common to Landing Gear

Landing gear is subjected to high levels of stress and corrosion, regardless of an aircraft’s size or type. Two key contributors to corrosion are temperature and mechanical stress, both of which continuously affect landing gear assemblies.

For instance, commercial jet brakes generate extreme heat. On a Boeing 767-200/300, steel brakes can reach operating temperatures of about 700°F, while carbon brakes can exceed 800°F.

Additionally, landing gear endures some of the highest mechanical stresses on the entire aircraft. It supports the immense weight during taxi, takeoff, and landing—sometimes carrying loads exceeding a million pounds—and absorbs the significant impact forces during landing.

According to the FAA’s Advisory Circular 43.4B, landing gear experiences more wear and tear than any other part of the aircraft. It not only bears mechanical stress but is also exposed to environmental hazards such as mud, salt, sand (especially in winter operations), gravel, and foreign object debris (FOD) from the runways.

Cleaning the Landing Gear

Brakes generate large amounts of dust and grime, coating everything around the landing gear. Cleaning this area presents a challenge, as using high-pressure wash equipment is prohibited: “High-pressure wash equipment shall never be used on the aircraft landing gear and components, wheels, and brakes, as they can force lubricants out of bearings and attach points, causing corrosion and wear problems” (USAF T.O. 1-1-691, pg. 3-29).

As my first crew chief supervisor once told me, cleaning the landing gear—known as “cleaning the whites”—is about more than just maintaining the aircraft’s appearance. A clean aircraft allows for more accurate inspections and may even help flight crew members detect potential failures. For instance, a cracked landing gear fitting hidden under layers of mud and grease could easily be missed (FAA Aviation Maintenance Technician Handbook-General).

Since high-pressure water is off-limits, what’s the best way to clean landing gear? Traditionally, tech wipes or rags soaked in hydraulic fluid were used to cut through grease, grime, and brake dust effectively. However, hydraulic fluid poses several hazards—it’s a known carcinogen, highly flammable, doesn’t evaporate, and can cause smoke or even fires if it contacts the brakes. It also damages tires, requiring them to be replaced if soaked, no matter the tread condition.

Cleaning Methods for Landing Gear

Pre-Saturated Wipes: A Safer Option

A safer and more effective alternative is to use pre-saturated wipes. These wipes evaporate quickly and reduce the risk of cross-contamination since they are disposable. Simply wipe down the struts, wheels, and other components, and discard the wipe when finished. By using this method, you can reduce the risk of contaminating tires or brakes with hydraulic fluid, while effectively degreasing landing gear components.

Maintaining Chrome on Struts

Clean the chrome frequently to keep the struts in good condition. Dirt and grime can build up, potentially causing seals to malfunction and leading to hydraulic leaks. This could result in a strut fully deflating, requiring you to deflate and reinflate all struts to maintain balance, which is a time-consuming process. To prevent this, it’s crucial to wipe down the chrome before refueling to stop grime from reaching the seals as the aircraft settles.

Non-Flammable Degreaser: Keeping Chrome Spotless

Using a non-flammable aerosol degreaser is an excellent solution for cutting through grime, keeping seals intact, and maintaining clean, spotless chrome.

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AVIOSOLV I

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Conclusion

In conclusion, degreasing landing gear, is vital for both aesthetic appeal and operational safety. Regular cleaning helps prevent corrosion, which poses a serious threat to the integrity of an airframe. By using safer and more effective cleaning methods, such as pre-saturated wipes and non-flammable degreasers, aircraft maintenance teams can enhance inspection accuracy and prolong the lifespan of key components. A well-maintained aircraft not only ensures smoother operations but also safeguards against hidden mechanical failures that could compromise flight safety.

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