This story was made in partnership with AOPA Pilot Protection Services. Make sure your certificates are protected before your next flight. Learn more and get started here. Derin Allard
Prop strikes can cause a lot of trouble for your engine and your wallet. Here’s what you need to know about them.
What Is a Propeller Strike?
Propeller strikes are one of the most expensive problems that can happen to propeller-driven aircraft. They usually require an engine overhaul, and they can make an airplane out of service for weeks or even months. Lycoming Service Bulletin 533C tells us what is considered a propeller strike (or sudden stoppage event) and what the required maintenance actions are.
According to Lycoming, these are the things that are considered propeller strikes:
- Any incident during engine operation where the propeller hits a solid object. This includes hitting the ground. Although the propeller can still turn, the engine can be damaged, and it might even fail.
- When the engine suddenly slows down when it hits water, tall grass, or a similar soft surface where the propeller usually doesn’t get damaged.
- Any incident, whether the engine is running or not, where the propeller needs to be repaired.
Propeller strikes can happen during many things, from a hangar door hitting a parked airplane (when the engine is not running) to a landing with the wheels up. A sudden stop can put a lot of force on the crankshaft of the propeller flange, the front bearing, and the seal. Poor control of the airplane during strong crosswinds or a bouncy landing are some of the most common causes of propeller strikes.
Wildlife Problems, Especially at Dusk
Wildlife on the runway is another big problem for propeller strikes. Animals are usually more active at sunrise, sunset, and at night, so it’s harder to see them when you’re taking off or landing.
Before landing, the pilots in the video below flew over the field to check the runway. But when they came back to land, deer started running across the runway as the pilots touched down in their Cessna 182. It was too late for a go-around, and the deer hit the propeller and the side of the airplane, causing damage.
We talked to the pilots, and they said there was a 3″ dent behind the cowling, more dents behind the door, and the deer hit the prop, which made the engine need to be taken apart. Luckily, everyone in the cockpit was okay.
Hidden Damage
The specific circumstances of a propeller strike can’t always be used to predict how much damage is inside the engine. The future reliability of the engine, not just how it is working now, is a big concern. The initial damage might allow the engine to keep running, but the problems could get much worse over time and with wear. Propeller strikes can range from not having much damage to causing a total failure.
The problem is that you can’t really know until you open up the engine. Generally, the crankshaft doesn’t get damaged easily in most engines. However, “some engine failures were caused by a crankshaft gear dowel that was too stressed and finally broke. When this part breaks, all power is lost. Because of this, Lycoming Service Bulletin No. 475C and AD Note 91-14-22 require a mandatory inspection and following the repair and assembly procedures.”
Required Inspections
Because of the high risks and no clear way to measure the damage to the engine, Lycoming has made several “Inspection Checklist After a Propeller Strike” documents. Before taking off again, a mechanic has to do a list of 30-40 inspections, depending on whether the engine is geared or not geared.
According to Lycoming, “any decision to operate an engine that was involved in a sudden stop, a propeller strike, or the loss of a propeller blade tip without disassembling and inspecting it will violate the AD Note issued by the FAA and Lycoming Service Bulletin No. 475C, which are both mandatory.”
What to Look for During Preflight
When you are pre-flighting an airplane, especially if it is a shared airplane, look carefully at the propeller for any damage. Check for dents, strange scratches or scrapes, warping, grass stains, damage to the tip, and more.
Even the smallest damage to a propeller can show that there is engine damage, which could lead to an engine failure.
Have You Seen a Propeller Strike?
Have you seen a propeller strike or the damage it caused? Tell us in the comments below.
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