Aircraft propeller maintenance procedures are strict and rigid – and for a good reason. Ensuring that the propellers of any craft are in optimum condition is essential for maintaining onboard safety. Propeller inspection is a vital part of this, as is taking measures to prevent damage and issues.
Corrosion is one of the most significant factors in the deterioration of propellers, and this can be expensive and dangerous. Luckily for you, here at Stockton Propeller, we make it our mission to keep you informed and educated. In turn, this means you can keep your aircraft in tip-top condition for longer.
What Is Corrosion?
In the simplest terms, ‘corrosion’ refers to the breakdown of a material – usually metal – due to a chemical reaction. Typically, this will involve the oxidation of metals with air or water molecules.
Corrosion can also occur when an acidic or base material comes into contact with something else. Corrosion impacts the physical properties of a material, making it weaker or less effective.
When it comes to aircraft, this can be very dangerous.
What Are Common Types of Propeller Corrosion?
There are many causes of aircraft propeller corrosion. Familiarising yourself with the most common will help you prevent them. These most common corrosion causes include:
1. Uniform Surface Attack
The most common type of corrosion, uniform surface corrosion, is caused by the metal’s exposure to the oxygen in the air. Uniform surface attacks usually occur where paint wears away from the surface.
Decay will be accelerated if the surface is not adequately prepared before painting. It can also be exacerbated if the propeller is exposed to high humidity, acids, or pollutants.
2. Intergranular Corrosion
This type of corrosion is less common but more disastrous. Once you have discovered it, it is usually too late to save the propeller.
Intergranular corrosion occurs between the grains or crystals of the materials and may appear in the presence of tensile stress. Here, cracks may occur along grain boundaries, and progress along the paths until total decay occurs.
This type of corrosion usually occurs as a result of chromium depletion and can be avoided using materials with less than 0.05% carbon.
3. Stress Corrosion
Stress corrosion is prevalent in highly stressed areas of the aircraft, such as propellers, engine crankshafts, or landing gears. Scratches or corrosion to the metal surface is usually the primary cause and can result in the component’s failure.
4. Crevice or Deposit Corrosion
Another common form of corrosion is a crevice, or deposit, corrosion, and can occur anywhere, which traps pollutants or moisture. Rivets and lapped skin joints are prime examples, and this can result in a weakening of the entire structure if left untreated.
5. Filiform Corrosion
The first sign of this is usually fine, worm-like lines or corrosion which show up under paintwork. Over time, this will turn into a bubbling, flaking surface, leading to long-term damage. Filiform corrosion is most commonly found on aluminum or magnesium surfaces, which have been inadequately prepared for polyethylene paints.
Reduce the Risk of Corrosion with Aircraft Propeller Maintenance Procedures
Corrosion can be catastrophic to an aircraft, especially when it occurs on the propeller. These are the heart of the craft, and a failure here can lead to tragedy in the air. Fortunately, there are steps you can take to help reduce the risk of corrosion, and these revolve around proper maintenance.
Wash Your Aircraft
Taking a little time to wash and care for your craft can really pay off in the long run. If you have undergone a long flight, make sure you rinse off the aircraft to remove any corroding agents.
Take extra time and care on propellers, do not use a pressure washer, and make sure these are treated with corrosion inhibitor products where appropriate.
Cleaning your propeller blades properly can help to increase their lifespan, and well as reducing corrosion. Different materials will have different requirements, as follows:
- Aluminum and steel propellers should avoid caustic or acidic materials, as well as steel brushes, steel wool, or power buffers. Instead, use a brush or cloth with a suitable cleaning solvent, and add a suitable polish if required. Once clean, coat the propellers in engine oil.
- Wooden propellers need warm water and mild soap, with a cloth or brush.
- Remember to rinse in freshwater as soon as possible if it has been in contact with salt water, and thoroughly dry once finished.
Covering your aircraft helps to protect it from the elements, and this can also be applied to propellers. Investing in quality propeller covers allows you to increase the lifespan of these parts and keep them safe from corrosive factors.
Keep The Aircraft As Dry As Possible
Staying dry can be easier said than done if you live in a damp climate, but it is essential to try. Make sure your craft is dried off thoroughly, and don’t leave propellers to simply ‘drip-dry.’
Carry Out Regular Propeller Inspections
Ultimately, implementing a strict, regular inspection and maintenance program is the easiest way to reduce corrosion. A scheduled propeller inspection plan will allow you to get to know the aircraft, flagging up any inconsistencies or changes immediately. It also allows you to treat corrosion as it arises, rather than leaving it to spread.
What Is Involved In A Propeller Inspection?
A regular inspection should include a visual overview of the propeller and any other security features. As a rule, you should check:
- Propeller blades and spinners for any grease deposits or the presence of excessive oils
- Weld and braze sections for evidence of weakness or failure
- For any scratches, nicks, or flaws on the propeller.
- Bolts and screws for tightness and proper safety.
- Ensure oil levels and lubricating requirements are sufficient.
Preventing Corrosion with Propeller Maintenance
Learning to undertake regular, thorough maintenance and inspections are crucial elements of owning an aircraft. At Stockton Propeller, we have the skills, experience, and equipment you need to keep your propellers in the best condition.
Get in touch today, and ask one of our experts how we can help keep your craft airborne for longer.