If you didn’t, it wasn’t because of your tires, it’s just because you have a greater prop clearance in that taildragger. Tires don’t sling up pebbles like props will.
Propeller Nick on freshly overhauled prop
- Thread starter PaulR035
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Flybuddy
Pre-takeoff checklist
Tires throw up rocks but generally back. I had a Velocity and it was recommended to fly without wheel pants for the first 10 landings since it helped reduce speed. We have a concrete runway which seems to regurgitate small chunks. For those first couple of weeks I must have repaired that prop (composite) about 5 times..After I put the wheel fairings on (and kept the belly door down), no more prop nicks.
Stewartb
Final Approach
That's totally wrong. Find any airplane that operates on gravel and take a close look at the dings. Most are inboard of the tips and most are on the back side of the blades. This I know for sure. Especially now with a composite prop. 100% of the dings are on the back side with only a few small ticks in the nickel leading edge, and none near the tips. And when I wore out my first set of Bushwheels on the 180 I switched to 29" AirHawks. For about 2 weeks. The increase in prop damage was impossible to miss, and it was related to the flatter profile of those tires. I went back to Bushwheels, and fast. The hardest thing I know of on my props? Water erosion at the tips when float flying, and that's from plowing and taxiing downwind.
If you haven't experienced rocks from your tires it may be because you fly little tires. Most guys who fly to unmaintained strips use bigger tires to PROTECT FROM using high power to taxi. If you use high power to taxi on soft surfaces? You'll learn. Aircraft equipment is a balancing act.
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Plano Pilot
Line Up and Wait
Back in the 80's I flew a KA200 into grass and gravel runways. We were told to open the ice vanes so any fod would go out the bottom of the engines. We were also told not to leave them open too long because with them open not as much airflow was going over the oil coolers.
kgruber
Final Approach
I flew them back then too. It appears that nowadays they open the ice vanes for all ops on the ground. Much more than we did.........only on gravel/dirt.
MauleSkinner
Touchdown! Greaser!
The newer-style cowls are much more effective at sucking in FOD.
Plano Pilot
Line Up and Wait
The most changeling nonpaved runway we flew into was the Murchison Ranch near Acuna, Mexico. I only went into there 3 times, the morning arrivals was fun. It was overcast and the tops of the hills were in the clouds. Previous pilots had made an unapproved approach using a radial and DME off Ciudad Victoria VOR, no GPS back then, that put you over the town of Gonzalez. From there you followed a river, into the hills under the overcast, to the airport. You needed to be configured for landing by the time you saw the water falls, make a turn to the right and there was the grass strip. I thought the approach was the worst until we got to the parking area, our KA did not have the big tires. After we stopped the ranch hands would place thick plywood ahead of the main gear, while the engines were running, and then we would taxi up on them! Last time I was there was for several days and we did not want the airplane to sink into the ground.
I was told that Clint had a DC-3 with JATO rockets that flew in years before. At the time I was flying for his widow Virginia Linthicum.
kgruber
Final Approach
We had "Hi Floatation" gear on our 200, and I managed to break through the pavement at Methow Valley State (S52) even with that! It also slowed us down about 20K in cruise.
Doc Holliday
En-Route
benyflyguy
En-Route
Yikes. Fortunate that happened on the ground!
Dan Thomas
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Dan Thomas
Thanks for posting that. Vivid proof of what an innocent-looking nick can do. If that blade had broken a minute later, in flight, they might all have died.
PaulS
Touchdown! Greaser!
A nick, also know as a stress concentrator, no bueno.
nrpetersen
Line Up and Wait
A leading edge nick is one thing, but once a crack is initiated at the bottom of the nick, the radius at the root of the propagated crack is so incredibly small that IMMEDIATE inspection and dressing action is required to salvage the damaged propeller. 2XXX series heat treated aluminums are especially vicious in their crack propagation/fracture toughness tendencies. The Kathryn's report pictures and micropix are the most spectacular examples of this I've ever seen. THX!
SoCal RV Flyer
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SoCal RV Flyer
Wow, that separated blade is sobering. The blade's face is pretty hammered with chips as well.
aftCG
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aftCG
I do, and for that exact reason.
Stewartb
Final Approach
Fake news? Lack of proper maintenance would be the cause of that blade break. It wouldn't happen instantly. Ding 'em, fix 'em. Ownership 101.
PaulS
Touchdown! Greaser!
Any updates???
Seanaldinho
Pattern Altitude
Whats fake news? The report says it is undetermined when the nick or fatigue crack occurred. Only that the pilot reported the propeller was fine.
Outside of that you can only go on the maintenance records which...
Stewartb
Final Approach
What was the outcome here? Did I miss it?
Dan Thomas
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Unfortunately, too many owners are poorly educated about such things, and their mechanics don't enlighten them. Plenty of CFIs don't know this stuff either. Any time I made a presentation to owners or students about the things to watch for, I had a rapt audience that wanted to know more. Nobody wants to buy or fly an unsafe airplane, or do dangerous things in flight through ignorance.
Stewartb
Final Approach
Being a gravel guy for the past 25 years? I run my hand down the leading edges of each blade before every flight. Old habit. It helps me understand why nicks happen and how to minimize them, too, I'm okay with itty bitty nick filing but for anything deeper than about a human hair's thickness? I let the mechanic do it. And I don't watch!
A friend of mine, Nicolas, was flying a rental C 150 over the Potomac river just south of DCA, years ago, and 6 inches of his prop went off and he killed the mags, full throttle for max turning load, and pulled up steep to near stall, all one motion. When the prop quit turning, he made a landing on a sand bar, and into shallow water.
The FBO tried to force him to pay for the recovery from the river. They held that he could have run the engine until near a landing site on dry land.
He was an ex fighter pilot, and a lawyer, and pointed out that the engine nearly destroyed the mounts, and if he had run it a little longer, the engine may have separated completely, and with that weight and balance, he would not have been flying.
They dropped the claim, and did not attempt to even collect the deductible that the rental agreement called for.
Several of my instructors were fanatics on searching for nicks, and both visual and rubbing the blade became standard for me. After Nicolas's prop failure, I was even more vigilant. I am also fond of rolling run ups if the taxiway is long enough.
The FBO tried to force him to pay for the recovery from the river. They held that he could have run the engine until near a landing site on dry land.
He was an ex fighter pilot, and a lawyer, and pointed out that the engine nearly destroyed the mounts, and if he had run it a little longer, the engine may have separated completely, and with that weight and balance, he would not have been flying.
They dropped the claim, and did not attempt to even collect the deductible that the rental agreement called for.
Several of my instructors were fanatics on searching for nicks, and both visual and rubbing the blade became standard for me. After Nicolas's prop failure, I was even more vigilant. I am also fond of rolling run ups if the taxiway is long enough.
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Domenick
I've never operated on gravel, and I do that too. It's been on my preflight checklist for 20 years.
PaulS
Touchdown! Greaser!
I check for nicks on every preflight, in fact before every flight. I rent, if I find one I report it. Unless the nick is deep, it is NOT a no-go item for me. But when I report them they are generally gone the next time I fly that airplane, which is a good thing in my book. Nicks are stress concentrators, which means the stress at that point can approach or exceed the yield strength and cause the material to crack. Stress concentrators are especially dangerous in areas that experience dynamic and/or cyclic loads, a prop is an extreme example of dynamic and cyclic loads. Once the material begins to crack it can progress quickly and catastrophically. Don't mess with prop nicks.
Ghery
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Ghery Pettit
Me too. My original CFI taught me to check and I've been doing so religiously ever since. About 20 years for me, too.
Props have node points, locations down the length of each blade where the blade will bend and vibrate continuously. Imagine bending a wire up and down at one point over and over. These are critical spots for damage. About 1/3 and 2/3 down the length of each blade.
Tom-D
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Tom-D
I have trouble believing that is a problem.
Gary Austin
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I just saw on Katheryn's report were a Cessna 185 in Alaska thew a blade on take-off, the pilot got the engine shut down, but not before a mount mount broke, that was a close call, another matter of seconds and it could/would have been a 3 person fatality, interesting, it broke 1/3 of the way out from the hub: below is a remark from the investigation: this was a McCauley prop and they are quoting from the mfg manual:
Even though a propeller may be operating normally and have a good external appearance when the TBO flight time or calendar limit is reached, operation beyond the specified TBO limits is not permitted.
The accident hub assembly and propeller blades do not have a published life limit that requires replacement. The hub assembly and propeller blades can be used indefinitely if an overhaul is performed every 1,500 hours or 60 calendar months (whichever occurs first), and all components remain in a serviceable condition.
It was undetermined why the propeller was not overhauled during the most recent 100-hour inspection (July 13, 2017 – 1,544.6 hours accumulated) or the second most recent 100-hour inspection (March 16, 2017 – 1,489.2 hours accumulated). For both inspections, the same airframe and powerplant mechanic (with inspection authorization), performed the work. Copies of the maintenance records are in the public docket for this accident.
So it looks like the IA got called up on this, Gary
Even though a propeller may be operating normally and have a good external appearance when the TBO flight time or calendar limit is reached, operation beyond the specified TBO limits is not permitted.
The accident hub assembly and propeller blades do not have a published life limit that requires replacement. The hub assembly and propeller blades can be used indefinitely if an overhaul is performed every 1,500 hours or 60 calendar months (whichever occurs first), and all components remain in a serviceable condition.
It was undetermined why the propeller was not overhauled during the most recent 100-hour inspection (July 13, 2017 – 1,544.6 hours accumulated) or the second most recent 100-hour inspection (March 16, 2017 – 1,489.2 hours accumulated). For both inspections, the same airframe and powerplant mechanic (with inspection authorization), performed the work. Copies of the maintenance records are in the public docket for this accident.
So it looks like the IA got called up on this, Gary
I believe the pics posted above in #49 are from this specific event.
Probably because the overhaul recommendation is not required to be followed under Part 91 ops. Accident investigations regularly mention all possible mx options (like SBs) regardless if they are legally required or not. Overhaul requirements start to come into play once a "maintenance program" is required for operations like Part 135.
nrpetersen
Line Up and Wait
Wrong this time. That IS the problem. I would have explained it a little differently but an extensive conversation with the chief engineer of McCauley 30 years ago brought it out when they were looking for a torsional vibration test system.
The vibration mode is best described as the rear of the crankshaft vibrating to-and-fro, while the prop tips vibrate fro-and-to in the chordal direction. The maximum cyclic stress is on the leading and trailing edges of the prop blade as it vibrates. A typical fixed blade prop on a crankshaft rings like a bell (except that it is a torsional ringing) at about 200 Hz - slightly below middle C on a piano.
I could hear the ~200 Hz harsh ringing at moderate power levels on our 172M - and you would be able too if I hummed and pointed it out to you. It was a narrow rpm range where it peaked out as that O-320 has no damper system on the rear of the crank. We just didn't run it there. Many other engine-propeller combinations have one or more damper systems to take care of similar vibrations. But they are all torsional
biplanebob
Pre-takeoff checklist
200Hz tone:
Gary Austin
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I remember CubCrafters having a problem with certain mags and the O-200 in the Sport Cub, something about
torsional vibration that something didn't like, I had one mag die while ferrying it to a new owner, Gary
torsional vibration that something didn't like, I had one mag die while ferrying it to a new owner, Gary
nrpetersen
Line Up and Wait
The back end of a crankshaft is a pretty rough ride and depending on the propeller selection, torsional vibration can be quite severe. It is the reason there is a rubber isolator in the drive to certain rear-mounted generators/alternators (i.e.Cont O-200s and O300s) and why some of the 470s eat accessory drive belts. Mounting the alt/generators up front gets a smoother ride but to a certain extent that has other torsional consequences for crankshaft stresses. A shirt tail relative lost half a blade very much like that pictured above on a Cessna 180 years ago.
Tom-D probably knows the practical details as applies to aircraft. I only know the theory and consequences of tuned mass (harmonic) dampers or lack thereof. Applying them is a little bit of a voodoo art.
FYI: There have been a number of ADs over the years on cracked props due to torsional vibrations. There is also a certification requirement on props to identify various vib freqs so that they don't overlap or compound their effects. Most vib issues are caught during the cert process which is where you will see set engine RPM limits with certain prop/engine combos. It is also the reason there are different damage zones on a prop due to what JAWS mentioned above. All in all a prop blade will last forever unless you get damage in certain areas which can cause a catastrophic failure like the one above. And believe it or not, a prop blade doesn't stay rigid under load as it is constantly flexing and tweaking due to physical and vibratory loads just like any powered item. And since you'll ask, here is one AD that was issued due vibration caused failure:
Tom-D
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Tom-D
Not debating that props fail.
But to quote a 54 AD, and one that has a hub, is a stretch
Tom-D
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Tom-D
Props such as the 150/172 fix pitch seldom fail, unless they have been damaged prior.The back end of a crankshaft is a pretty rough ride and depending on the propeller selection, torsional vibration can be quite severe. It is the reason there is a rubber isolator in the drive to certain rear-mounted generators/alternators (i.e.Cont O-200s and O300s) and why some of the 470s eat accessory drive belts. Mounting the alt/generators up front gets a smoother ride but to a certain extent that has other torsional consequences for crankshaft stresses. A shirt tail relative lost half a blade very much like that pictured above on a Cessna 180 years ago.
Tom-D probably knows the practical details as applies to aircraft. I only know the theory and consequences of tuned mass (harmonic) dampers or lack thereof. Applying them is a little bit of a voodoo art.
why? they are maintained properly, and inspected regularly.
Tom-D
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Tom-D
A real "no sh-t " story.
At OKH a mooney with a 180 Lycoming did a near gear up. he left 6 big gouges on the runway and made a go-around. after he got it on the ground they discovered both blades were bent 90 degrees. I told the pilot that I would remove the prop. and deliver it to Northwesters prop shop.
nope he elected to have another A&P straighten the blades, and fly it down to the shop.
when the prop shop heard about it they told the FSDO, FSDO had a fit, but the A&P never signed the return to service, and he got away with it.
At OKH a mooney with a 180 Lycoming did a near gear up. he left 6 big gouges on the runway and made a go-around. after he got it on the ground they discovered both blades were bent 90 degrees. I told the pilot that I would remove the prop. and deliver it to Northwesters prop shop.
nope he elected to have another A&P straighten the blades, and fly it down to the shop.
when the prop shop heard about it they told the FSDO, FSDO had a fit, but the A&P never signed the return to service, and he got away with it.
Stewartb
Final Approach
With Lightspeed solid state electronic ignition?
Stewartb
Final Approach
Bump.