Propeller dings
Dallas
I've read all the warnings about propeller dings and cracks but nothing
I've read talks about what magnitude constitutes a danger.
For example, the last time I looked the prop on the airplane I fly it had
ding. It was not a dent ding, but more like a straight line groove on the
leading edge. It was tiny, like someone took the edge of a file and gave
it half a push over the leading edge.
I was sure it was not enough to be a problem but it got me thinking, how
big would it have to be before you wouldn't fly it?
--
Dallas
Jack Allison
> I was sure it was not enough to be a problem but it got me thinking, how
> big would it have to be before you wouldn't fly it?
>
FWIW, the owner's manual for our Hartzell prop says "Nicks, gouges, and
scratches on the blade surface or on the leading or trailing edges of
the blade, greater than 1/32 inch wide or deep, must be removed before
flight.
In a video that came with the prop, they also say that as a rule of
thumb, if you can catch your fingernail in the nick/groove/whatever, you
should have it looked at.
So, at least this is what Hartzell has to say...
--
Jack Allison
PP-ASEL-Instrument Airplane
Student - CP-ASEL
"To become a Jedi knight, you must master a single force. To become
a private pilot you must strive to master four of them"
- Rod Machado
(Remove the obvious from address to reply via e-mail)
Jim Macklin
if you struck the prop blade with a knife or axe, it would have a sharp V,
which is a serious stress riser. The stress will concentrate in the V and
lead to a stress failure. A nick that is U shaped like a round rock, that
was made as a dent rather than a cut is less critical and can wait if the
dent is not more than twice as deep as it is wide [until the next 100
inspection].
ANY prop repair must follow the maker's manual and be done by a certified
mechanic, it should recorded in the logbook.
--
James H. Macklin
ATP,CFII-ASMELI, A&P
BE400/BE1900-BE300
"Jack Allison" <k2boar...@rem0ve.th1s.gmail.com> wrote in message
news:Do6dnbRwn-rM2vDa...@comcast.com...
Dan_Thom...@yahoo.com
<p51mustang[threeX12]@xxxhotmail.calm> wrote:
> Any sharp nick should be repaired before flight, visualize what would happen
> if you struck the prop blade with a knife or axe, it would have a sharp V,
> which is a serious stress riser. The stress will concentrate in the V and
> lead to a stress failure. A nick that is U shaped like a round rock, that
> was made as a dent rather than a cut is less critical and can wait if the
> dent is not more than twice as deep as it is wide [until the next 100
> inspection].
>
> ANY prop repair must follow the maker's manual and be done by a certified
> mechanic, it should recorded in the logbook.
We're fussy about nicks, but I see a lot of airplanes with props
that look like they've been mixing cement. As with a lot of damage to
airplanes, it's the severity of damage multiplied by time that is the
key. A tiny nick would have to be flown for a long time before a crack
developed, and large nick would take much less time. There are nicks I
see that I would not fly at all before repairing. And I see lots of
improperly-dressed-out nicks that are no safer than if they'd been
left alone. Round-bottomed dings I don't like, either, since the metal
is compressed and work-hardened and can crack more readily. I found
stone embedded in one such dent, making it deeper than it appeared.
The stone filled it somewhat.
One of our prop shops has a blade from a cropsprayer that had
about 10" break off. The pilot flew it back to base and was ticked
that the shop didn't have another in stock. I've wondered about the
damage to the airframe and engine mounts on that airplane. Such
vibration breaks things. He's lucky the engine stayed put.
Another story has it that a cropsprayer was shot at by an irate
farmer, and when he landed he found a bullet hole in the blade. He
dressed it neatly, rounding the edges and polishing it and finished
out the season. The propshop guys who saw it next were appalled, of
course.
Dan
Dallas
wrote:
> One of our prop shops has a blade from a cropsprayer that had
> about 10" break off.
There was some talk around our FBO last month about an aircraft in the mid
cities area of our city that lost a prop tip and went down... ripped the
engine right off the mounts and sent the aircraft down with nothing but an
empty firewall. I guess that kinda screws up the center of gravity.
--
Dallas
Hilton
http://www.youtube.com/watch?v=t0txEC0Rhdg
Dave Morss described this in a seminar. IIRC, he immediately shut down the
engine and pulled it up into an almost stall to stop the prop. A while
later he put the gear down but the nose wheel light did not come on. He
yawed the plane back and forth (you can see this in the video) - didn't
help. He said he was pretty stupid/lucky (in hindsight) because the engine
was hanging on by a thread and he was lucky that it did not fall off because
of the sideslip forces while yawing.
Anyway, it's not a vibration, it's a pretty violent event. Imaging this in
IMC.
Hilton
Dallas
> http://www.youtube.com/watch?v=t0txEC0Rhdg
Ugh! That's something in real life you never want to see.
Except for the landing... that you do want to see.
--
Dallas
Roger (K8RI)
<Cybnorm@spam_me_not.Hotmail.Com> wrote:
>
>I've read all the warnings about propeller dings and cracks but nothing
>I've read talks about what magnitude constitutes a danger.
Officially, anything that requires more than a *minor* dressing of the
prop is supposed to require an engine tear down.
You use a find file to trim the area until the nick is no longer
visible and then use progressively finer emery cloth until the area is
polished. You aren't supposed to leave file marks either.
I've forgotten the rules for width versus depth now, but I don't
believe that's something the owner/pilot has the privilege of fixing.
Roger (K8RI)
Roger (K8RI)
Some years back a Lancair 320 lost the prop South of Oshkosh (on the
way home). Tore the engine right out of the mounts. I believe it was
the same plane that used to race down at Sun n' Fun. No survivors.
Roger (K8RI)
Jim Macklin
minor repair, it is not preventative maintenance allowed an owner pr pilot.
You must draw file rather than across the edge of the blade and you must
maintain the profile. A nick 1/8" deep requires IIRC, a draw filed length
of almost 2" centered on the nick. Then it must be smoothed to remove even
file marks.
See AC 43.13-x and the prop manuals of the maker for that model.
"Roger (K8RI)" <valida...@my.com> wrote in message
news:ihutm3hs7nj8fnhcf...@4ax.com...
Brian
> Officially, anything that requires more than a *minor* dressing of the
> prop is supposed to require an engine tear down.
>
While I am not a mechanic I am quite sure the above statement is
false. I have seen at least 3 different mechanic return 4 different
engines to service after the props were bent at about 45 degrees. Two
of them with the same prop after it had been straighted. One was bent
in a gear up landing, The other was a Citabria that rolled over in the
snow, the third and fourth were after dropping the nose wheel into a
hole and dinging/bending prop. I believe the procedure may vary
between engine manufacturers but I assisted the mechanic in inspecting
the Citabria crankshaft with a dial indicator.
Brian
CFIIG/ASEL
Dan_Thom...@yahoo.com
The AC43.13 rules for prop nick repairs in the blade
edge call for the repair width to be 10 times the depth, with the
depth of repair being at least .002" below the lowest damage. If the
nick is in the blade face or back, the repair will be spoon-shaped, 30
times the depth spanwise and 10 times chordwise.
Prop manufacturers specify the maximum bends that can be
straightened, but ll work must be done by a prop shop. So many degrees
per length of blade. And NDI afterward to look for cracks.
A Lycoming AD specifies that the crankshaft gear retaining
bolt be inspected if there's any propstrike, along with the gear
dowel. Their definition of strike includes "'water, tall grass or
similar yielding medium." In many cases this requires engine teardown.
Many crankshafts have broken after propstrikes, sometimes years later.
It happened to me. Dialling a crank guarantees nothing, since the
crank can bend enough to start a crack and snap back to within the
"accepted" limits.
Dan
Roger (K8RI)
wrote:
><snip>
>> Officially, anything that requires more than a *minor* dressing of the
>> prop is supposed to require an engine tear down.
>>
><snip>
>
>While I am not a mechanic I am quite sure the above statement is
>false. I have seen at least 3 different mechanic return 4 different
At one time and I believe it is still true although they may have
changed it. If it takes more than a minor redressing an engine
teardown is required. The instances mentioned are far more than
minor. Prior to this the tear down was required only if there was an
engine stoppage under power
>engines to service after the props were bent at about 45 degrees. Two
>of them with the same prop after it had been straighted. One was bent
>in a gear up landing, The other was a Citabria that rolled over in the
>snow, the third and fourth were after dropping the nose wheel into a
>hole and dinging/bending prop. I believe the procedure may vary
>between engine manufacturers but I assisted the mechanic in inspecting
>the Citabria crankshaft with a dial indicator.
I think you will find this is not accepted practice as far as both
Lycombing and Continental are concerned. Whether the crank is straight
or not the concern is the stress that was imposed on the crank with
the prop strike.
Roger (K8RI)
>
>Brian
>CFIIG/ASEL
Brian
> It happened to me. Dialling a crank guarantees nothing, since the
> crank can bend enough to start a crack and snap back to within the
> "accepted" limits.
>
Interesting? Are crankshafts really hardened the point they will crack
before they will yeild?
I would think that would make them very difficult to machine during
the manufacturing process.
I could see the crankshaft yielding radially due to a sudden stoppage
at high RPM or Power and I agree in these situations the engine must
be torn down. But all of the situations I have seen were at Idle power
or less.
I am also sure the temptation in these situations is still to not tear
down as that is very expensive. This could easily lead to the
situation you described.
I am aware of two more situations that have occured in the past few
months locally. I will have to see if a teardown was done on either of
these.
Brian
Dan_Thom...@yahoo.com
The cranks are hardened after maching, using a process
called nitriding. \\\\but it's a very thin hard layer and doesn't
contribute much to the cracking. \the cranks is designed to drive a
prop to move air, not to withstand the remote possibility of striking
something hard or substantial, \they'd be far too heavy if they were
made to take that.
\\some cranks, like the small Continentals, are known to
crack at the REAR of the crank after a strike, not near the front. And
propstrikes often cause accessory gearing damage at the back of the
engine. The only reasonable thing is to tear it down. We've found
cracked cranks after such incidents.
Dan
Jim Macklin
a hard surface, some are heat treated.
If you have a prop strike, failing to do an engine teardown might cost you
your life. But if the teardown doesn't find damage, your insurance might
not pay.
You can damage the nose seal on the engine and damage CS prop bearings by
pulling on the prop, what do you suppose happens when 100 pounds of rotating
mass with a 4 foot arm hits a solid object, forces are extreme.
"Brian" <brian...@msn.com> wrote in message
news:321e915a-ac91-44ad...@s8g2000prg.googlegroups.com...
Brian
>
> If you have a prop strike, failing to do an engine teardown might cost you
> your life. But if the teardown doesn't find damage, your insurance might
> not pay.
>
While thinking about this I have recalled 5 more incidents where props
were bent or contacted the ground at Idle power or less and the
engines were not torn down. This is in addition to the 4 I previously
mentioned.
Summary:
C-182 dropped nosewheel into hole while taxiing
C-182 Same thing, different C-182.
Tomahawk Taxied through Rain gutter and hit Prop on Pavement
Citrabria - Oil Seal Failed, emergency landing in snow, Airplane
rolled over.
GlassAir III - Fuel Starvation Lead to Gear up Landing.
Aeronca Champ put up on nose, Stuck prop into the dirt.
Aeronca Champ Prop contacted pavement during wheel landing.
Citabria Prop contacted pavement during wheel landing
So now I am up to 9 prop strikes without the engine being torn down
with the last 15 years. In fact I can't recall a single prop strike at
idle power or less where the engine was torn down. I still need to
research to 2 recent ones.
So I find it very difficult to believe that a tear down is required.
If it is, then my experince is that in practice it is usually ignored.
I certainly can't and won't argue that a teardown is not a good idea.
It just appears to me that in most cases the mechanics and owners are
deciding that the risk is not high enough to justify the cost.
Brian
Peter Clark
wrote:
>While thinking about this I have recalled 5 more incidents where props
>were bent or contacted the ground at Idle power or less and the
>engines were not torn down. This is in addition to the 4 I previously
>mentioned.
>
>Summary:
>C-182 dropped nosewheel into hole while taxiing
>C-182 Same thing, different C-182.
>Tomahawk Taxied through Rain gutter and hit Prop on Pavement
>Citrabria - Oil Seal Failed, emergency landing in snow, Airplane
>rolled over.
>GlassAir III - Fuel Starvation Lead to Gear up Landing.
>Aeronca Champ put up on nose, Stuck prop into the dirt.
>Aeronca Champ Prop contacted pavement during wheel landing.
>Citabria Prop contacted pavement during wheel landing
>
>So now I am up to 9 prop strikes without the engine being torn down
>with the last 15 years. In fact I can't recall a single prop strike at
>idle power or less where the engine was torn down. I still need to
>research to 2 recent ones.
>
>So I find it very difficult to believe that a tear down is required.
>If it is, then my experince is that in practice it is usually ignored.
The language of Lycoming SB533A ("Recommendations Regarding Accidental
Propeller/Rotor Strike or Loss of Propeller/Rotor Blade or Tip") says
that Lycoming's position is that anything that requires more than
minot dressing should be torn down and inspected, and if you don't
then it's on whomever returned it to service without the inspection if
something happens. I haven't looked at Continental's site.
Michael Ash
> I certainly can't and won't argue that a teardown is not a good idea.
> It just appears to me that in most cases the mechanics and owners are
> deciding that the risk is not high enough to justify the cost.
If the insurance companies aren't paying for it then it's a pretty good
bet that the risk isn't all that high. Not that they give one whit about
your personal safety and welfare, but if the engine suddenly decides in
the middle of cruise that, hey, it really *didn't* appreciate that prop
strike, the insurance company is going to be the one buying the aircraft
after the ensuing accident. They have access to all the aggregate
statistics needed to make the most economical choice, and if they're
deciding that it's not worth paying some small fraction of the aircraft's
total value to be sure that the engine is still in good shape, then you
can be pretty sure that the added risk is below that fraction. Whether
this corresponds with your personal desire for safety is another question
altogether, but it's at least a data point to consider.
--
Michael Ash
Rogue Amoeba Software
Dave Stadt
"Jim Macklin" <p51mustang[threeX12]@xxxhotmail.calm> wrote in message
news:c8xcj.24663$Wt7....@newsfe14.phx...
> There are cast steel cranks and forged steel cranks. Some are nitrided
> for
> a hard surface, some are heat treated.
>
> If you have a prop strike, failing to do an engine teardown might cost you
> your life. But if the teardown doesn't find damage, your insurance might
> not pay.
If you have decent insurance it provides for engine teardown after a prop
strike.
Morgans
>> If you have a prop strike, failing to do an engine teardown might cost
>> you
>> your life. But if the teardown doesn't find damage, your insurance might
>> not pay.
> If you have decent insurance it provides for engine teardown after a prop
> strike.
That sure jives with all that I read, and hear. If the insurance does not
pay, then they aren't a great insurance company. Of course, that is about
par for insurance company, now days.
While teardowns are required for flat 4's and 6's, that is not necessarly
true for the big radials. Their short, stout crankshafts are better at
taking the punishment of a prop strike without damage. Somewhere, there are
charts that give the RPM and nature of the strike, then tell you if a
teardown is recomended. It is necessary to use a dial indicator, and see if
there is excessive runout on the prop flange, though.
Please note that I am not an A & P, but am just relating what I have read on
the subject, and heard on the subject of prop strikes on this forum,
previously.
I sure hope that the OP's relaying what he has seen about prop strikes on
the planes he has been around do not bite someone on the butt. With that
many cases, I would think that the chances of at least one breaking would be
pretty dang high. I don't think the opposed engine manufacturers are just
covering their butts, on this one.
--
Jim in NC
Jim Macklin
The question should not be "how little can I do?" and should be "What is the
least I can pay for the required maintenance done properly?"
"Dave Stadt" <dhs...@ameritech.net> wrote in message
news:KeFcj.81477$Um6....@newssvr12.news.prodigy.net...
Roger (K8RI)
<p51mustang[threeX12]@xxxhotmail.calm> wrote:
>Lots of people buy cheap insurance. Some people even buy cheap maintenance.
>The question should not be "how little can I do?" and should be "What is the
>least I can pay for the required maintenance done properly?"
And here I am... I've always followed a progressive maintenance
program as well as telling the mechanic at annual time, "If you find
something that should be fixed, fix it."
Of course I had to explain that was not the same as saying "Money is
no object!". <:-))
>
>
>
>
>"Dave Stadt" <dhs...@ameritech.net> wrote in message
>news:KeFcj.81477$Um6....@newssvr12.news.prodigy.net...
>|
>| "Jim Macklin" <p51mustang[threeX12]@xxxhotmail.calm> wrote in message
>| news:c8xcj.24663$Wt7....@newsfe14.phx...
>| > There are cast steel cranks and forged steel cranks. Some are nitrided
>| > for
>| > a hard surface, some are heat treated.
>| >
>| > If you have a prop strike, failing to do an engine teardown might cost
>you
>| > your life. But if the teardown doesn't find damage, your insurance
>might
They may have a maximum they will pay for a tear down whether damage
is found or not. I was in a 5-way partnership in a Cherokee 180 when
one of the *other* members had a prop strike. The Insurance paid for
a tear down but with only a couple hundred hours to go to TBO we
elected to have the major done at that time.
Roger (K8RI)
Brian
> While teardowns are required for flat 4's and 6's, that is not necessarly
> true for the big radials. Their short, stout crankshafts are better at
> taking the punishment of a prop strike without damage. Somewhere, there are
> charts that give the RPM and nature of the strike, then tell you if a
> teardown is recomended. It is necessary to use a dial indicator, and see if
> there is excessive runout on the prop flange, though.
>
That reminds me of another one where I watch an Ag Cat taxi into an
alumium Saw horse. While it bent the saw horse in half and threw it
about hundred feet, we couldn't even see that it nicked that prop.
Brian
Dan_Thom...@yahoo.com
> If the insurance companies aren't paying for it then it's a pretty good
> bet that the risk isn't all that high. Not that they give one whit about
> your personal safety and welfare, but if the engine suddenly decides in
> the middle of cruise that, hey, it really *didn't* appreciate that prop
> strike, the insurance company is going to be the one buying the aircraft
> after the ensuing accident. They have access to all the aggregate
> statistics needed to make the most economical choice, and if they're
> deciding that it's not worth paying some small fraction of the aircraft's
> total value to be sure that the engine is still in good shape, then you
> can be pretty sure that the added risk is below that fraction. Whether
> this corresponds with your personal desire for safety is another question
> altogether, but it's at least a data point to consider.
So it comes down to this: do you want to risk being a minor
statistic?
As I mentioned earlier, I had a crank break in flight due to an
old propstrike that hadn't been properly addressed. And we have had
propstrikes on airplanes in our fleet that caused us to tear them
down, and found cracked cranks between a third and half of the time.
Doesn't sound like a minor statistic to me. I'm a Canadian AME,
equivalent to A&P-IA. I don't want another crank breaking on me. It
might not be over such benign territory next time.
Dan
Brian
FORGIVENESS IS AVAILABLE WHEN ACCIDENTS HAPPEN
As AOPA member Richard Massman taxied his airplane, it picked up a
tiedown rope, causing a metal hook to catch and damage the tip of the
prop. "There was minimal fault on my part," said Massman, who
experienced the prop strike accident earlier this year at Clearwater
Air Park in Clearwater, Fla. "But I was concerned about whether I
should even file a claim because I thought it might work against me."
When Massman called an AOPA Insurance Agency representative for
advice, he received authorization "in a heartbeat" to get the prop
fixed on an immediate basis without any hassles. What Massman didn't
know is that he could take advantage of the AOPA Accident Forgiveness
and Deductible Waiver Enhancement Program, just for participating in
qualifying AOPA Air Safety Foundation safety education every six
months
Notice they said " to get the prop fixed" not "to tear down the
engine"
Maybe the did, but that isn't what it says.
Brian