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“Prop strike.” These two words are guaranteed to make any pilot wince. A propeller strike is dangerous, not only because it damages the propeller but also because it can cause hidden damage that may lead to catastrophic engine failure.

While no one wants to experience a prop strike, the fact is, accidents happen. Knowing how prop strikes occur and what steps to take after an incident can help you avoid potentially dangerous and expensive situations.

What is a propeller strike?

You might think that a prop strike is simply when the propeller blades hit something. But there’s a little more to it. Each major engine manufacturer provides specific directives on what constitutes a propeller strike and what maintenance steps are required post-strike.

As an example, Lycoming defines a prop strike as:

• Any incident, whether or not the engine is operating, where repair of the propeller is necessary.
• Any incident during engine operation where the propeller has impact on a solid object. This incident includes propeller strikes against the ground. Although the propeller can continue to turn, damage to the engine can occur, possibly with progression to engine failure.
• Sudden RPM drop on impact to water, tall grass, or similar yielding medium where propeller damage does not usually occur.

Always refer to your manufacturer’s recommendations if you experience or suspect a prop strike.

How do prop strikes happen?

Propeller strikes can happen to anyone. Sometimes they are preventable, but sometimes they aren’t. Here are some common scenarios when propeller strikes happen: 

• Landing mishaps. Many prop strikes are the result of gear-up landings, ground loops, or nosegear first landings. Practicing good, consistent landings is the best way to avoid these problems.
• Poor ground clearance. Consider the type of flying you do. If you plan to do a lot of backcountry flying, landing on unpaved surfaces and soft-field airstrips, selecting a propeller with good ground clearance is critical.
• Tow bar strikes. More than one pilot has made the embarrassing (and potentially dangerous) mistake of starting up with the towbar attached. A rule of thumb: if the towbar is on your airplane, your hand is on the towbar. It’s always a good idea to do a final walk-around of the aircraft after you complete the preflight.
• Foreign object debris. Be aware of loose gravel and other debris like trash, stray tools, and metal screws on the ground near your aircraft. Clear them away to avoid the risk of propeller nicks or damage to nearby airplanes or people caused by prop wash. When taxiing on the runway, look for obstructions and potholes in your path.
• Wildlife strikes. Animals on the runway can be a major prop strike problem, especially in the early morning or nighttime hours, when it’s harder to see. Look out for birds, deer, and even stray cats or dogs that may cross your path.

What should you do in the event of a prop strike?

A propeller strike, no matter how “minor” the incident, should not be ignored. Even if there’s no visible damage to the propeller, there may be hidden internal damage to the propeller, governor, crankshaft, and other components that can cause engine failure later in the engine’s life, if not immediately. After a prop strike event, a complete propeller inspection is required. Depending on the damage revealed in the inspection, the propeller may need to be removed, disassembled, and overhauled by a certified propeller repair station. Never try to straighten bent propeller blades or tips yourself. It’s dangerous, not to mention illegal.

Most engine manufacturers also strongly recommend or require an engine tear-down inspection following any prop strike, sudden stoppage, or loss of propeller blade tip. You truly can’t find out if there’s interior engine damage until you open up the engine. Like most airplane maintenance decisions, it’s better to be safe than sorry. In a tear-down inspection, a skilled mechanic will remove and disassemble the engine to complete a detailed internal inspection of the reciprocating and rotating parts. From there, a complete engine overhaul may be necessary. As with all maintenance and repair concerns, refer to your propeller and engine manufacturer’s guidelines.

Lastly, be careful when purchasing a pre-owned airplane with a prop strike in its history. Be sure you understand what happened during the incident and how it was repaired. Having a pre-purchase inspection performed by a qualified mechanic can help reduce your personal and financial risk.

If you have technical questions about your Hartzell propeller, we’re happy to help. Get in touch with our technical team by emailing techsupport@hartzellprop.com.