Is your Aircraft Propeller due for an Overhaul? Hours or years?
Aircraft propellers have recommended overhaul intervals based on calendar time and flight hours. Depending upon the propeller model, this interval could be between 1,000 to 2,000 flight hours; but, there is also a calendar limit (typically five years) that is often ignored. Ignoring the calendar limit can be a serious problem in an aircraft that flies, on average, fewer than 100 hours per year. At 100 hours per year, a typical 2,000-hour prop might not get inspected for 20 years! This is clearly a bad idea. A propeller should be overhauled at either the time or calendar limit, whichever occurs first. If the engine comes up for overhaul before the prop reaches either limit, most shops will recommend removing the propeller and governor and having them overhauled when the engine is overhauled.
Corrosion Is Often the Culprit
Aircraft propeller overhaul periods deserve respect because what destroys most props is not external defects, but unseen internal corrosion. Dissimilar metals in the prop and hub create an environment ripe for corrosion, and the only way to properly inspect these areas of a propeller is through a teardown. Extensive corrosion can dramatically reduce the strength of the blades or hub. Even minor corrosion may cause a blade or hub to fail inspection.
Because of the safety implications, airplane propeller safety is clearly not an area in which to skimp. Remember, corrosion can be internal in critical blade retention components. Such conditions present both a hidden defect and a potential safety-of-flight issue. This is the primary reason that calendar limits are an important inspection requirement. Also, the overhaul needs to include more than just a corrosion inspection. Restoration of paint and plating are important to assure future corrosion protection until the next overhaul.
Looking for cracks and corrosion using dye penetrant and a black light during the airplane propeller overhaul process
