An aircraft propeller is a significant investment for any aircraft owner. However, its increased safety and efficiency make the expenditure worthwhile. Aircraft propellers are exposed to many structural and mechanical damages, making them the most vulnerable component of your aircraft. That’s why it's vital that you take extra care of it to make it last longer.
There are several types of corrosion attacks that an aircraft propeller can face. Knowing the most common ones can help you identify them and take the timely repair steps so as not to lose the whole propeller to these corrosions.
What Is An Aircraft Propeller?
An aircraft propeller is an aerodynamic device that converts rotational energy into propulsive energy. A propeller creates a thrust that is almost perpendicular to the plane of rotation. A propeller can directly be attached to the crankshaft of the piston engine (as in almost all light aircraft) or may be powered by a reduction gearbox. They are responsible for your smooth in-air experience and decrease shockwave formation and their impact on aircraft significantly. In fact, the aircraft can not fly without a propeller.
Various types of aircraft propellers are available in the market including:
- Fixed-pitch
- Wooden propellers
- Metal propellers
- Ground adjustable propellers
- Controllable pitch propellers
- Constant speed propellers
- Reverse-pitch propellers
- Feathering propellers
What Are The Common Types Of Propeller Corrosion?
Some of the most common types of propeller corrosions include
Uniform Surface Attack
This is by far the most common type of aircraft and propeller corrosion. This occurs when the surface comes in contact with oxygen in the air. This happens on the parts where paint wears away from the surface.
Propeller decay is accelerated if the surface is not adequately prepared before painting. Uniform surface attack corrosion can also be exacerbated if the aircraft is exposed to high humidity, acids, and pollutants.
Intergranular Corrosion
This is the least common type of corrosion but most disastrous. By the time you discover this type of corrosion, it is already too late to save the propeller.
This corrosion occurs from within the grains and crystals of the material and is usually present where there is tensile stress. In intergranular corrosion, cracks develop along grain boundaries and continue to spread until the complete decay of the material.
The main cause of this corrosion is chromium depletion that occurs in the presence of carbon. Intergranular corrosion can be avoided by making the propeller with materials that have less than 0.05% carbon.
Stress Corrosion
As the name suggests, this type of corrosion is prevalent in the high-stress areas of the aircraft, such as the engine crankshaft, landing gear, and propellers. The main causes of this corrosion are scratches or corrosion on the metal surface, this can ultimately result in component failure.
Crevice Or Deposit Corrosion
Another type of propeller and aircraft corrosion is crevice or deposit corrosion. It can occur anywhere, and traps pollutants and moisture. Corroded rivets and lapped skinned joints are prime examples of crevice corrosion. This can easily spread to the whole structure and weaken it if left unchecked or untreated.
Filiform Corrosion
Last on the list is filiform corrosion. The first sign of this corrosion is usually fine, wormlike lines on the body of the propeller or corrosion under the paintwork. Over time these lines will convert into bubbling, material flakes resulting in long-term and greater damage.
Filiform corrosion is commonly found on aluminum or magnesium surfaces that have been poorly made and prepared for polyethylene paints.
Conclusion
Corrosion can badly impact the most important and expensive part of your aircraft; your propeller. Fortunately, you can prevent corrosion and its damage by being preemptive, when it comes to your aircraft and propeller maintenance.
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