Prop Strike? Action?

M

Magman

Pattern Altitude
Joined
Oct 30, 2020
Messages
1,734
Display Name
Display name:
Magman
A CFI taxied a friends aircraft into the hangar. Some type of cardboard was sucked into the Prop and was shredded. The LOUD noise caused some folks to investigate. They later found that a substantial amount of the cardboard was tossed in a trash can. The owner was not notified.

A bud asked me of what action he would advise the owner to take. I have not seen it but I believe it to be a Lyc 172. Initial reports say no visual damage anywhere. My thoughts are:

At a MINIMUM ; verify Propeller Track is correct.

Lycoming AD 91-14-22 ( or revision) required inspection of the Crankshaft Gear IF the Prop had to be removed for repairs. That does not appear to be the case here though.

Other courses of action other than banning CFI from the area?
 
If it didn’t cause any sudden stoppage, than it’s *probably* okay. Heck, a deer ran through my prop and got sliced in two and the engine didn’t suffer any damage after being evaluated by a teardown and inspection. These engines are a lot more stout than some folks give credit for!
 
RyanB said:
If it didn’t cause any sudden stoppage, than it’s *probably* okay.
Click to expand...

"Probably" ... :dunno:

Lycoming gives one note for prop strikes as, "Sudden RPM drop on impact to water, tall grass, or similar yielding medium where propeller damage does not usually occur"

This may help: https://www.lycoming.com/sites/default/files/SB533C Recommended Action for sudden Engine Stoppage, Propeller_Rotor Strike or Loss of Propeller_Rotor Blade or Ti (1).pdf

Edit: Thanks to Dan for his reply.
 
RyanB said:
If it didn’t cause any sudden stoppage, than it’s *probably* okay. Heck, a deer ran through my prop and got sliced in two and the engine didn’t suffer any damage after being evaluated by a teardown and inspection. These engines are a lot more stout than some folks give credit for!
Click to expand...
The teardown and inspections came about because of incidents like I once had. I had a crankshaft break in flight, and we found the break had started and progressed over a long time. There was rust in the earlier parts of the break faces, indicating some age to it. It was due to a old propstrike of some sort. We had a couple of students run off the runway in 150s, both of them into snowbanks, and both cranks were cracked.

On the other hand, another fellow groundlooped his airplane, tearing out a gear leg and dropping the prop onto the pavement under some power. The crank was OK. The prop was a real mess.

The takeaway here is that you cannot safely say that "it will be OK." Dialling the crank for runout has been proven to be useless. The crank can twist and deform considerably and spring back, but a crack might have started. Engine overhaulers find this sort of stuff. Nice straight cranks with cracks in them.

There are other considerations. Magnetos and vacuum pumps and alternators have momentum, too, and can be damaged by propstrikes, especially where the prop struck something solid where the RPM dropped really suddenly.
 
Daleandee said:
"Probably" ... :dunno:

Lycoming gives one note for prop strikes as, "Sudden RPM drop on impact to water, tall grass, or similar yielding medium where propeller damage does not usually occur"

This may help: https://www.lycoming.com/sites/default/files/SB533C Recommended Action for sudden Engine Stoppage, Propeller_Rotor Strike or Loss of Propeller_Rotor Blade or Ti (1).pdf

Edit: Thanks to Dan for his reply.
Click to expand...
Note the asterisks around the word ‘probably’, which indicates no absolutes and is purely an assumption based on my own experience of a running engine and propeller making contact with an object far, far more hard and dense than cardboard, and no damage was done. I am not suggesting any specific course of action here. YMMV.
 
Daleandee said:
"Probably" ... :dunno:

Lycoming gives one note for prop strikes as, "Sudden RPM drop on impact to water, tall grass, or similar yielding medium where propeller damage does not usually occur"

This may help: https://www.lycoming.com/sites/default/files/SB533C Recommended Action for sudden Engine Stoppage, Propeller_Rotor Strike or Loss of Propeller_Rotor Blade or Ti (1).pdf

Edit: Thanks to Dan for his reply.
Click to expand...

Do you really think that cardboard (that's light enough to get sucked into the prop) is going to cause a sudden RPM drop? It ain't even gonna know it's there.

PaulS said:
Who taxis into a hangar?
Click to expand...

Someone who is taxiing a plane into a hangar. :D

I've seen guys taxi through the open hangar door opening into the hangar without contacting the structure of said hangar.

Not sure how much stock I would put in Lycoming when they can't even use the right spelling of hangar.
 
Last edited:
EdFred said:
Do you really think that cardboard is going to cause a sudden RPM drop? It ain't even gonna know it's there.
Click to expand...

The engine manufacturer mentions "tall grass, or similar yielding medium where propeller damage does not usually occur" so just maybe the substantial amount of carboard found in the trash did have an impact. I dunno but I think cardboard may be a bit more stout than tall grass ...
 
Daleandee said:
The engine manufacturer mentions "tall grass, or similar yielding medium where propeller damage does not usually occur" so just maybe the substantial amount of carboard found in the trash did have an impact. I dunno but I think cardboard may be a bit more stout than tall grass ...
Click to expand...

Not if it's getting sucked up and blown around. A blade of tall grass, sure, a field or bunch of it, not so much. I've run over cardboard with my lawnmower and it didn't even hiccough, but when I roll over a wad of grass clippings it chokes it out.

Take a carboard box and give it a tear. Pretty easy. Take a 6" diameter clump of tall grass and try and tear it and tell me which is more stout.

Also, better do a teardown if you taxi through a spiderweb - it's stronger than steel.
 
Daleandee said:
The engine manufacturer mentions "tall grass, or similar yielding medium where propeller damage does not usually occur" so just maybe the substantial amount of carboard found in the trash did have an impact. I dunno but I think cardboard may be a bit more stout than tall grass ...
Click to expand...
That was probably written by a lawyer, not an engineer.
 
Daleandee said:
The engine manufacturer mentions "tall grass, or similar yielding medium where propeller damage does not usually occur" so just maybe the substantial amount of carboard found in the trash did have an impact. I dunno but I think cardboard may be a bit more stout than tall grass ...
Click to expand...
IMO, the relevant fact is that the only person who knows what happened apparently can’t be trusted to tell people.
 
EdFred said:
Not if it's getting sucked up and blown around.
Click to expand...

We do not know what happened and we have guidance from the manufacturer as to prop strikes. Would you totally ignore this situation? What would you advice the OP given the information you have available?
 
Daleandee said:
The engine manufacturer mentions "tall grass, or similar yielding medium where propeller damage does not usually occur" so just maybe the substantial amount of carboard found in the trash did have an impact. I dunno but I think cardboard may be a bit more stout than tall grass ...
Click to expand...
I will repeat, and I’m not making any suggestions either way, but I was flying an airplane a few years ago and ran smack dab into a full grown deer during landing. The engine was subsequently torn down and inspected and there was zero damage from the strike.

Again, I’m not suggesting any particular course of action, but if the hind legs of a deer slicing through a running propeller didn’t cause any damage, I’m quite certain cardboard wouldn’t either.
 
MauleSkinner said:
IMO, the relevant fact is that the only person who knows what happened apparently can’t be trusted to tell people.
Click to expand...

What would they tell them? I've sucked up paper on the ramp and shredded it. I didn't bother telling anyone because there was no RPM drop.
 
Daleandee said:
We do not know what happened and we have guidance from the manufacturer as to prop strikes. Would you totally ignore this situation? What would you advice the OP given the information you have available?
Click to expand...

It was stated the cardboard was sucked up, meaning it was pretty damn light. It wasn't tied to the earth like a clump of grass, or a dense like a frozen snowbank, and certainly doesn't have the stopping power of the body of water. I would 100% ignore it based on what was posted.

Guys cut rolls of toilet paper with props, are they doing a teardown afterwards? No. Now if guys are cutting a CASE of toilet paper still in the shrink wrap, then yeah. But a piece of cardboard? *keyshawnjohnsongif*

More forces going on when starting the aircraft than hitting some loose cardboard, but we aren't tearing down after every engine start.
 
Last edited:
EdFred said:
It was stated the cardboard was sucked up, meaning it was pretty damn light.
Click to expand...

Again ... we do not know what happened. So, unlike you, I cannot give information as to what should/shouln't be done. I'm certain I would not totally ignore it. I value the safety of myself and my passengers too much for that. Perhaps I'm just overcautious.
 
Daleandee said:
Again ... we do not know what happened. So, unlike you, I cannot give information as to what should/shouln't be done. I'm certain I would not totally ignore it. I value the safety of myself and my passengers too much for that. Perhaps I'm just overcautious.
Click to expand...

Well I mean if we want to say we never know what ever happens ever when the plane is not under 24/7 monitoring we should should do a tear down as part of very preflight since we...........don't know what happened. It was posted it was sucked up...but now the goalposts are on the baseball field next door.
 
EdFred said:
Well I mean if we want to say we never know what ever happens ever when the plane is not under 24/7 monitoring we should should do a tear down as part of very preflight since we...........don't know what happened.
Click to expand...

You are getting into being obtuse now.

The truth is we don't know if there was an RPM drop, we don't know how heavy the cardboard was, we don't know how much cardboard was sucked up, we don't know the condition of the engine, etc.

There was a builder that cranked his plane in the hanger and sucked his wings into the prop that were a fair distance away against the wall.

There likely isn't anything here to be concerned about but I'd want to do a little more detective work before I gave it the "OK to fly my family in it" seal of approval. You do you.
 
Daleandee said:
There was a builder that cranked his plane in the hanger and sucked his wings into the prop that were a fair distance away against the wall.
Click to expand...
Very much apples to oranges in comparison, like not even close to being similar (cardboard vs airplane wings). :dunno:
 
Daleandee said:
You are getting into being obtuse now.

The truth is we don't know if there was an RPM drop, we don't know how heavy the cardboard was, we don't know how much cardboard was sucked up, we don't know the condition of the engine, etc.

There was a builder that cranked his plane in the hanger and sucked his wings into the prop that were a fair distance away against the wall.

There likely isn't anything here to be concerned about but I'd want to do a little more detective work before I gave it the "OK to fly my family in it" seal of approval. You do you.
Click to expand...

Start up the engine. Throw equivalent cardboard into prop and monitor the RPM. If it suddenly drops (it won't) do the teardown. You aren't going to cause any additional damage. And now there's no guessing. Cheap, easy, effective.
 
RyanB said:
Very much apples to oranges in comparison, like not even close to being similar (cardboard vs airplane wings). :dunno:
Click to expand...

My point is that wings are heaver than cardboard and that a running prop in a hangar can pull all kinds of things into it including cardboard heavy enough to possibly do damage.

"They later found that a substantial amount of the cardboard was tossed in a trash can."
 
Daleandee said:
Now that's a great plan ... :rolleyes:
Click to expand...

You wanted to know what happened. That's the only way to know short of video evidence. You've already taken the position that the person taxiing the plane can't be trusted. So your options are that - which replicates what happened - or spending 10k on a teardown NOT knowing what happened. If it requires a teardown, you will know so by duplicating the incident.

You said/implied you wanted to know what happened. Now you will know. And the second incident isn't going to be the cause.
 
EdFred said:
You wanted to know what happened. That's the only way to know short of video evidence. You've already taken the position that the person taxiing the plane can't be trusted. So your options are that - which replicates what happened - or spending 10k on a teardown NOT knowing what happened. If it requires a teardown, you will know so by duplicating the incident.

You said/implied you wanted to know what happened. Now you will know. And the second incident isn't going to be the cause.
Click to expand...

Well ... Fearless Tower in post #24 had a great solution!
 
EdFred said:
I would counter with "if something is found I (the CFI) will pay for it (because there was no RPM drop) if nothing is found it's your dime."

You may want to grab some cardboard.
Click to expand...

Your idea .. I'll watch from my EZ chair. ;)
 
Do you think the fact that the noise was LOUD enough to have folks come running is a clue?
I’m unsure of the pre-strike form of the cardboard. Box or large sheet is unknown.
The trash can contained a lot.

Pilot was Airline Pilot /CFI.
 
Last edited:
EdFred said:
What would they tell them? I've sucked up paper on the ramp and shredded it. I didn't bother telling anyone because there was no RPM drop.
Click to expand...
“I sucked up some cardboard from the hangar, but there was no change in RPM, and I didn’t see any damage to the airplane.”

but since the instructor had to be “caught” in order to get the first part, I wouldn’t trust the instructor on the second and third parts.
 
MauleSkinner said:
“I sucked up some cardboard from the hangar, but there was no change in RPM, and I didn’t see any damage to the airplane.”

but since the instructor had to be “caught” in order to get the first part, I wouldn’t trust the instructor on the second and third parts.
Click to expand...

And that's why I asked what are they going to tell them, because now no one is gonna believe it because they are "obviously trying to cover something up," except maybe the didn't mention anything because, well, nothing happened. So nothing to tell. Honestly, I probably would have been "caught" too. Because, well, yawn. That's my take on it on the outside, that would be my take on the inside.
 
You must log in or register to reply here.
Back
Top