Where do propeller dings come from?

SixPapaCharlie

SixPapaCharlie

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Probably a dumb question.

I hear "xyz field is all gravel, it is going to chew up your propeller"
Prop is the front most portion of the plane and the wheel is rotating a direction more likely to fling debris rearward.

I have seen many pits and dings in my propeller and I don't really know where the majority of them come from.
 
Watch beneath a propeller on a wet ramp sometime. You'll see a little tornado. Doing your runup would create an even stronger force below the prop.
 
Before you start rolling you have to add power, vortexes at propeller tips pick up rocks like a tornado so some end up in front then get sucked through and hit the blade tips.
 
The air the prop pushes was first sucked from in front of the prop, and the prop tips create the same vortex that wing tips do and suck up the gravel from the ground into the prop.
 
So are the sea planes w/ engines up top immune?
 
bnt83 said:
How many have you looked at?

Pretty shiny Grumman Albatross here and the nastiest paint on the whole thing is located on the props.
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Water erosion. bet there wasn't a stone with in a mile.
 
Stones, pebbles, taxiway lights, bolts, etc. (Okay maybe not bolts, but have you ever done a FOD walk on a runway? Scary :yikes:

Erosion is a real thing though, sand and grit makes for a very rough leading edge on the prop. As mentioned above, precip of any kind is just really hard on leading edges in general. If you have a composite prop without a metal leading edge it doesn't take long for it to become noticeable.
 
Sac Arrow said:
Hah. What was the depth of the water? I'll take a case of Trumer's Pils, thank you.
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The spray off the sides of the hull gets into the props. That's all it takes--spray. Rain will take the paint off a prop, too.

Dan
 
I have watched small stones 12 or 18 inches behind the propeller roll forward under the prop and then get sucked into the front. The tip vortex on the prop would look like a doughnut if you could see it.

Taildraggers suffer this sort of damage a lot less than trikes. More prop clearance.

Dan
 
Dan Thomas said:
The spray off the sides of the hull gets into the props. That's all it takes--spray. Rain will take the paint off a prop, too.

Dan
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Yep, water droplets at speed will clean the paint right off aluminum. The boat I docked on CNN in the middle of huricane Frances got the Awl Grip stripped off the windward side down to bare metal, and a prop leading edge is going way faster than that wind.
 
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Most of my dings come from flying in the rain. The rear of the prop and the leading edge get it the most.
 
Also keep your stick back when you're doing a run up, down elevator can chuck crap back into your prop.

Personally I've always done rolling run ups as well as taxied around to warm my plane up, the area right infront of my hangar where I start up is kept well swept.

Now with the amphib I'm high enough off the ground to not really have that issue, but still something to keep in mind.
 
SixPapaCharlie said:
Probably a dumb question.

I hear "xyz field is all gravel, it is going to chew up your propeller"
Prop is the front most portion of the plane and the wheel is rotating a direction more likely to fling debris rearward.

I have seen many pits and dings in my propeller and I don't really know where the majority of them come from.
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I'm surprised that no one has answered this in standard 6PC humor fashion...
 
I am talking about the leading and trailing edge where it gets "Serrated" for lack of a better term
 
SixPapaCharlie said:
....I have seen many pits and dings in my propeller and I don't really know where the majority of them come from.
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Clark1961 said:
I'm surprised that no one has answered this in standard 6PC humor fashion...
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I'll try...........

from dingleberries?



















(sorry, that's actually eman1200 humor, which apparently only HE thinks is funny)
 
Most rock/gravel dings come from rocks being picked up and tossed over the top of the tire towards the prop. There's a sweet spot for speed depending on the conditions but it's more prevalent at taxi and fast taxi speeds than other times. Unless you rev up the plane on gravel with the brakes set the chance of lifting rocks is small. Gravel ops require a slow advance of the throttle. That's why you usually see STOL contests on clean pavement where guys can use full power and full brakes until brake release. Humidity and temperature will change the stickiness of the tires and can make rock dings worse on some days than others. Rain and mud are bad. Days with frost are the worst. Frosty gravel makes lots of dings. Tires with treads are worse than slicks, too. Having run both I can attest to that.
 
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Sac Arrow said:
Hah. What was the depth of the water? I'll take a case of Trumer's Pils, thank you.
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Understood. I once stood on a carrier deck and a young sailor said "that's a lot of water" I answered with " And you are just looking at the top of it"

But rocks on the bottom seldom are a problem for props, hopefully :)
 
Well, the mommy ding and the daddy ding fall in love. Then the daddy ding puts his ringading in mommy's special place...
 
Stewartb said:
Most rock/gravel dings come from rocks being picked up and tossed over the top of the tire towards the prop. There's a sweet spot for speed depending on the conditions but it's more prevalent at taxi and fast taxi speeds than other times. Unless you rev up the plane on gravel with the brakes set the chance of lifting rocks is small. Gravel ops require a slow advance of the throttle. That's why you usually see STOL contests on clean pavement where guys can use full power and full brakes until brake release. Humidity and temperature will change the stickiness of the tires and can make rock dings worse on some days than others. Rain and mud are bad. Days with frost are the worst. Frosty gravel makes lots of dings. Tires with treads are worse than slicks, too. Having run both I can attest to that.
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Yup, and with all that being said landing on gravel a few times with proper technique shouldn't cause extra wear on the prop or airplane. It's really not a big deal, unless you're 'tarded.
 
An old timer with a bazillion hours in dozens of different aircraft once told me to do my runups at 100' AGL to save the prop from dings. He finally hung up his wings after 55 years of incident-free flying when he could no longer physically climb in and out of a plane due to old age and arthritis.
 
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Simply get the aircraft moving forward prior to coming in with all the power.

Never set in gravel, hold the brakes, and go to full throttle.

I don't do that even on hard stuff.

If 15-20 feet means that much to your take off roll, you are walking way too close to the edge.
 
DavidWhite said:
Yup, and with all that being said landing on gravel a few times with proper technique shouldn't cause extra wear on the prop or airplane. It's really not a big deal, unless you're 'tarded.
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Landing,,,, you should be at idle, stones don't jump up at idle.
 
Stones don't jump. They get spun by tire rotation. It has nothing to do with power setting.
 
Stewartb said:
Stones don't jump. They get spun by tire rotation. It has nothing to do with power setting.
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Yup. When it's really cold outside you can hear the rocks getting flung into the prop by the tires. Not sure why it is, cold rocks stick to cold rubber really well I guess.
 
Landing on the beaches.... we have really coarse sand, shells, rocks and wood. The sand really does a job on the props.

I thought I was doing good until I found a really big gottcha on one blade the other day.

We have mud flaps on the oversized tundra tires to help keep the rocks from flying.

Had some passengers that had never been in a small plane before, they thought the beach landing was really cool and actually applauded after I shut down the engine.
 
There are several ways rocks get picked up, but the over whelming majority of the dings on props are from prop tip vortices, when you are moving prior to full power, the stones will miss the prop and hit the bottom of the fuselage.

to really appreciate this, you must watch a Spad (AD-1) on the cat.
 
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