C172 vs Drone

ppragman

FLIPY FLAPS!
This doesn't look like drone damage, it looks like land on nosewheel with too high a descent rate damage and got the prop?

Unless I see drone pieces I'm going to be sceptical because I can't really see how a 8lb quadcopter could for his much damage. Plus it looks an awful lot like the damage done to the 172 that just forgot to flare I saw a few years ago.

My only other idea is that maybe the blade catastrophically failed and then the engine ate itself, that is unlikely, but it does happen.
 

TUCKnTRUCK

That guy
We initially thought it was prop failure. They think they found rust in the prop. The NTSB is doing its thing now
I bet they are! What airport? Most drones won’t fly that close to anything more than a private airport now


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TUCKnTRUCK

That guy
This doesn't look like drone damage, it looks like land on nosewheel with too high a descent rate damage and got the prop?

Unless I see drone pieces I'm going to be sceptical because I can't really see how a 8lb quadcopter could for his much damage. Plus it looks an awful lot like the damage done to the 172 that just forgot to flare I saw a few years ago.

My only other idea is that maybe the blade catastrophically failed and then the engine ate itself, that is unlikely, but it does happen.
Usually a strike will bend the metal, not snap it off clean. There would be evidence of twisting/damage in the remaining stub.

This is either a failure in the metal, or damage which resulted in vibration at a resonant frequency. Resonance will destroy a prop catastrophically in exceptional ways.


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fholbert

Mod's - Please don't edit my posts!
This doesn't look like drone damage, it looks like land on nosewheel with too high a descent rate damage and got the prop?

Unless I see drone pieces I'm going to be sceptical because I can't really see how a 8lb quadcopter could for his much damage. Plus it looks an awful lot like the damage done to the 172 that just forgot to flare I saw a few years ago.
It may not be a drone but it’s definitely not a prop strike.
 

ppragman

FLIPY FLAPS!
This is either a failure in the metal, or damage which resulted in vibration at a resonant frequency. Resonance will destroy a prop catastrophically in exceptional ways.
The only reason I mention the impact damage is because it looks a lot like what I saw several years ago, but you probably have the better answer there, it's quite likely I'm out to lunch. I'm a bit curious about resonance being an issue, though?

You know, I've actually never heard of resonance being an issue on light airplanes that didn't have radials, you have any links about resonance on GA airplanes? I'd love to read more, I know it's an issue on the larger 4-bladed PT6s occasionally (I'm looking at you D model 1900), but never heard it being an issue on GA airplanes.
 

TUCKnTRUCK

That guy
The only reason I mention the impact damage is because it looks a lot like what I saw several years ago, but you probably have the better answer there, it's quite likely I'm out to lunch. I'm a bit curious about resonance being an issue, though?

You know, I've actually never heard of resonance being an issue on light airplanes that didn't have radials, you have any links about resonance on GA airplanes? I'd love to read more, I know it's an issue on the larger 4-bladed PT6s occasionally (I'm looking at you D model 1900), but never heard it being an issue on GA airplanes.
I think EPI has a few pages dedicated to vibration and resonance, discussing how instantaneous torque pulses from Piston aircraft can make it super challenging, in that a prop that works on a lycoming may come apart on a similar continental etc.

During a bunch of my engineering and design classes we got to watch videos of vibration surveys being done on static prop blades. They would put chalk on them so you could see where the nodes were. Some of the tests to failure were eye opening. Like breaking glass

When you excite metals there can be some really interesting results. Aluminum especially so because it won’t exhibit any stress or fatigue until it fails.


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TUCKnTRUCK

That guy
It may not be a drone but it’s definitely not a prop strike.
The drone wouldn’t snap the prop off, but I suppose the right type of damage from an impact could set off vibrations or such, resulting in the blade coming apart. If it bent or deflected the blade enough, altered track or pitch then it’s a grey area. I’ve seen really messed up props fly, but that’s not to say a small amount of just the right damage couldn’t cause a catastrophic failure.


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Roger Roger

Paid to sleep, fly for fun
The drone wouldn’t snap the prop off, but I suppose the right type of damage from an impact could set off vibrations or such, resulting in the blade coming apart. If it bent or deflected the blade enough, altered track or pitch then it’s a grey area. I’ve seen really messed up props fly, but that’s not to say a small amount of just the right damage couldn’t cause a catastrophic failure.


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That’s the only way I see this being drone related. I’ve seen aluminum props that hit solid pavement at takeoff power and didn’t have a clean break like that-that’s a fatigue failure of some type.
 

fholbert

Mod's - Please don't edit my posts!
That’s the only way I see this being drone related. I’ve seen aluminum props that hit solid pavement at takeoff power and didn’t have a clean break like that-that’s a fatigue failure of some type.
Or prop defect since new. The prop looks like new or recently overhauled.

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CFI A&P

Exploring the world one toilet at a time.
I’ve never seen a blade needing dressed that close to the hub.
All depends on where the nick or damage is. Each manufacturer has instructions for continued airworthiness to address dressing the blades.

This doesn't look like drone damage, it looks like land on nosewheel with too high a descent rate damage and got the prop?

Unless I see drone pieces I'm going to be sceptical because I can't really see how a 8lb quadcopter could for his much damage. Plus it looks an awful lot like the damage done to the 172 that just forgot to flare I saw a few years ago.

My only other idea is that maybe the blade catastrophically failed and then the engine ate itself, that is unlikely, but it does happen.
An aluminum blade doesn't break off from just a prop strike. There is an AD against McCauley "gullwing" propellers on the C152s that requires repetitive inspections due to cracks at the hub. Which is why you'll see a Sensenich on most C152s. Prop strike damage to a metal propeller is easy to identify: if the contact occurred with the engine at idle, it bends the tip aft and with power it bends the tip forward. Composite blades (MT, some Hartzels, Catto, Whirlwind, etc.) the composite blade will splinter and break off.

Or prop defect since new. The prop looks like new or recently overhauled.

View attachment 51123
That is a vintage McCauley logo, which wouldn't normally be placed on a recent overhaul. However they are available as reprints and available through a couple online sources.

@ppragman my stinson had an avoid range (RPM) because of the Met-L prop, due to resonance.
That was a Franklin 165.
This is actually fairly common. Most 2 blade Hartzell aluminum two blades with a compact hub on the 4cyl Lycomings have a prohibited range due to resonance. Such as the PA28R-200s. It does impact a few others. I fly an airplane with a 6cyl Lycoming and 3 blade MT that also has a RPM restriction.
 

ppragman

FLIPY FLAPS!
All depends on where the nick or damage is. Each manufacturer has instructions for continued airworthiness to address dressing the blades.



An aluminum blade doesn't break off from just a prop strike. There is an AD against McCauley "gullwing" propellers on the C152s that requires repetitive inspections due to cracks at the hub. Which is why you'll see a Sensenich on most C152s. Prop strike damage to a metal propeller is easy to identify: if the contact occurred with the engine at idle, it bends the tip aft and with power it bends the tip forward. Composite blades (MT, some Hartzels, Catto, Whirlwind, etc.) the composite blade will splinter and break off.



That is a vintage McCauley logo, which wouldn't normally be placed on a recent overhaul. However they are available as reprints and available through a couple online sources.



This is actually fairly common. Most 2 blade Hartzell aluminum two blades with a compact hub on the 4cyl Lycomings have a prohibited range due to resonance. Such as the PA28R-200s. It does impact a few others. I fly an airplane with a 6cyl Lycoming and 3 blade MT that also has a RPM restriction.
Out of curiosity, what are some of the physics reasons for the way the tip bends during strike? I've always known that bent tips we're indicative of a strike, but I did not know that power setting changed the direction of Bend, what's the physics of that? Got any resources? That's really really cool.
 

Roger Roger

Paid to sleep, fly for fun
Out of curiosity, what are some of the physics reasons for the way the tip bends during strike? I've always known that bent tips we're indicative of a strike, but I did not know that power setting changed the direction of Bend, what's the physics of that? Got any resources? That's really really cool.
It’s just the aoa of the blade. High power/high aoa the “face” (aft side) of the prop hits so the tips bend forward. Low power/negative aoa the “back” (forward) side hits and bends the blade backwards. Aluminum is very flexible which is why it bends instead of breaks. The only way to get a break like that is to make the aluminum brittle-and the most common way of doing that is fatigue.
 

CFI A&P

Exploring the world one toilet at a time.
Out of curiosity, what are some of the physics reasons for the way the tip bends during strike? I've always known that bent tips we're indicative of a strike, but I did not know that power setting changed the direction of Bend, what's the physics of that? Got any resources? That's really really cool.
If you give me a little bit of time I could find some big fancy engineering & science worthy words, but it in a nutshell the rigidity of the metal is compromised at the time of the contact and the material bends in the direction of thrust (forward) or drag (terra firma).
 

NovemberEcho

Dergs favorite member
It looks like it got bent back first and did a rotation or two taking parts of the cowl off before it snapped
 

TUCKnTRUCK

That guy
It looks like it got bent back first and did a rotation or two taking parts of the cowl off before it snapped
If you watch a motor move with only one blade left, you’re be surprised it’s still in the plane. Good chance that damage happened after the prop left. You can see how not centered that motor is now.

Motor mount in that airplane is toast, probably has a decent amount of firewall damage as well (without seeing it).

Depending on the year, that planes probably a write off.


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NovemberEcho

Dergs favorite member
If you watch a motor move with only one blade left, you’re be surprised it’s still in the plane. Good chance that damage happened after the prop left. You can see how not centered that motor is now.

Motor mount in that airplane is toast, probably has a decent amount of firewall damage as well (without seeing it).

Depending on the year, that planes probably a write off.


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good point, now that I look closer the damage matches with where the broken tip is.
 
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