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Runup on Snow


chrisk

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4 hours ago, ArtVandelay said:

Maybe the oil isn’t circulating, but there is oil going in and out of the hub.


Tom

Indeed there is, but it’s a very small quantity. It’s a sealed system and the prop hub always contains oil.The amount of additional oil required to go from the fine pitch stops to course would be measured in ounces. In the case of a Lycoming, those few onces of oil are pumped from the governor on the rear of the engine through an external hose to an AN fitting at the front of the case which supplies oil to the prop via the crank.  Perhaps oil from the governor does make it all the way to the hub, but my guess is very little given the volume of the system that feeds the hub and the low volume of the hub.  It likely matters little anyway unless you’re operating conditions so brutal that your engine is already suffering.

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21 hours ago, gsengle said:

 


Watch the oil temp gauge when you cycle the prop in cold weather. You have to confirm that it can flow, more than it is to warm it up per se, fresh oil moving. You’ll see the temp drop. I’m surprised that the feather check is so low, most prop hubs you don’t want to actuate to below 1000 rpm, the check is more like 1700 rpm


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I think you’re confusing oil temp with oil pressure. I see an oil pressure drop whenever rpm drops whether it’s done with the prop or the throttle. I have never witnessed an oil temperature drop when cycling the prop. Given my understanding of how the prop on my machine works, I’ll just say that a drop in oil temp from cycling the prop seems highly unlikely.

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I think you’re confusing oil temp with oil pressure. I see an oil pressure drop whenever rpm drops whether it’s done with the prop or the throttle. I have never witnessed an oil temperature drop when cycling the prop. Given my understanding of how the prop on my machine works, I’ll just say that a drop in oil temp from cycling the prop seems highly unlikely.


Nope, I’m not.


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On 1/20/2019 at 9:40 PM, gsengle said:

 


Nope, I’m not.


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You’re running a continental with a governor on the front of the case. Perhaps there’s something specific to that set up that causes an oil temp drop though I can’t imagine what. If I was running that set up, I’d make it my business to find out. Is it your contention that cold oil is leaving the prop cavity and flowing past the oil temp prob?

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18 minutes ago, Shadrach said:

Indeed there is, but it’s a very small quantity. It’s a sealed system and the prop hub always contains oil.The amount of additional oil required to go from the fine pitch stops to course would be measured in ounces. In the case of a Lycoming, those few onces of oil are pumped from the governor on the tar of the engine through an external hose that starts to an AN fitting at the front of the case which supplies oil to the prop via the crank.  Perhaps oil from the governor does make it all the way to the hub, but my guesses very little given the volume of the system that feeds the hub and the low volume of the hub.  My guess is that it matters a little anyway unless you’re operating condition so brutal that your engine is already suffering.

Not to be picky, but if the flow is as little as you suggest, how does the crankshaft get so full of sludge?  As I understand it there is continuous oil flow from the governor through the front bearing and the crankshaft transfer tube.

Clarence

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You’re running a continental with a governor on the front of the case. Perhaps there’s something specific to it that set up that causes an oil temp drop though I can’t imagine what. If I was running that set up, I’d make it my business to find out. Is it your contention that cold oil is leaving you prop cavity and flowing past the oil temp prob?


TSIO-540VB I believe, three bladed full feathering. They all behave that way. It’s noticed because it can take me right out of the green and delay departure until the temp comes back up.


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On 1/20/2019 at 9:58 PM, M20Doc said:

Not to be picky, but if the flow is as little as you suggest, how does the crankshaft get so full of sludge?  As I understand it there is continuous oil flow from the governor through the front bearing and the crankshaft transfer tube.

Clarence

I too have observed the sludge that you speak of.  Perhaps @Cody Stallings can speak to its formation. Any oil flowing in the flange is ostensibly in a closed centrifuge, so the fact that particulate accumulates there does not surprise me.

So it’s your understanding that the governor pressurizes the front bearing and the prop hub? It’s always been my assumption that there was a separate journal for governor pressure oil to the prop. I’m sure you’ve removed many more props than me, but the ones that I have removed have:

1) always been full of oil no matter how long the bird has been sitting.

and 

2) Had a single pathway to and from the hub’s cylinder (like a hydraulic line to an actuator). 

If I've been misinformed or have misunderstood the system, then I look forward to clearing up my misunderstanding. 

Just to clarify, I've never suggested that it’s a bad idea to pull the prop control through. I do it during taxi at 900 RPM and the prop goes course just like it does at 1700. The business of sitting in the run-up area jockeying your prop vernier back-and-forth multiple times at high rpm is something I find useless. I pull during taxi and watch rpms fall from 900 to 600.  That tells me all I need to know. I've flown airplanes with governors that start to “hunt”  before but that typically shows up in the takeoff roll not the run up. 

Same deal with the mags. I taxi with the engine very lean. The fact that the engine will run on either mag and at roughly the same or rpm with the mixture leaned so far back tells me that the mags are functioning reasonably well and closely timed. A relatively even EGT rise across all cylinders running on each mag tells me the ignition switch is working and that I am actually switching from a dual ignition source to a single ignition source.  A high power, inflight LOP mag check reveals a great deal more about the condition of the whole ignition system. 

I’ll add that if I was flying a new to me airplane, I would do everything by the book. Given that I’ve been flying my current airplane for about 14 years I know it very well.  I’ve developed what I believe are superior and less abusive methods of verifying its airworthiness.  To each their own, I posed the question to get some discussion going. If doing a run up in the snow is a challenge, why not first ask yourself why you’re doing the run up. For some people the answer is “because I always have”. My answer to that is “fair enough” but this is why I do it differently.

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1 hour ago, gsengle said:

 


TSIO-540VB I believe, three bladed full feathering. They all behave that way. It’s noticed because it can take me right out of the green and delay departure until the temp comes back up.


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Good to know. Full feathering is a different animal. The flow is reversed. My hartzell is against the fine pitch stops until the governor takes it off the stops. I believe your prop is the opposite. As to the oil temp drop from green to yellow from a hub that likely holds well under a pint of oil, I can’t say. My hub operates on onces of oil actuating a counter sprung piston. The oil moving back and forth through the crank to actuate it has never had any impact on oil temp that I can recall. I’ll surely double check though the next time I fly.

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1 hour ago, Shadrach said:

I too have observed the sludge that you speak of.  Perhaps @Cody Stallings can speak to its formation. Oil flowing through the flange is ostensibly in a closed centrifuge, so the fact that particulate accumulates there does not surprise me.

So it’s your understanding that the governor pressurizes the front bearing and the prop hub? It’s always been my assumption that there was a separate journal for governor pressure oil to the prop. I’m sure you’ve removed many more promise than I have, but the ones that I have removed have:

1) always been full of oil no matter how long the bird has been sitting.

and 

2) Had a single pathway to and from the hub’s cylinder (like a hydraulic line to an actuator). 

If I’ve been misinformed or have misunderstood, then I look forward to clearing up my misunderstanding. 

Just to clarify, I’ve never suggested that it’s a bad idea to pull the prop control through. I do it during taxi at 900 RPM and the prop goes course just like it does at 1700. The business of sitting in the run-up area jockeying your prop vernier back-and-forth multiple times at high rpm is something I find useless. I pull during taxi and watch rpms fall from 900 to 600.  That tells me all I need to know. I’ve flown airplanes with governors that start to “hunt”  before but that typically shows up in the takeoff roll not the run up. 

Same deal with the mags. I taxi with the engine very lean. The fact that the engine will run on either mag and at roughly the same or rpm with the mixture leaned so far back tells me that the mags are functioning reasonably well. A relatively even EGT rise across all cylinders running on each mag tells me the ignition switch is working and that I am actually switching from a dual ignition source to a single ignition source.  A high power, inflight LOP mag check reveals a great deal more about the condition of the whole ignition system. 

I’ll add that if I was flying a new to me airplane, I would do everything by the book. Given that I’ve been flying my current airplane for about 14 years I know it very well.  I’ve developed what I believe are superior and less abusive methods of verifying its airworthiness.  To each their own, I posed the question to get some discussion going. If doing a run up in the snow is a challenge, why not first ask yourself why you’re doing the run up. For some people the answer is “because I always have”. My answer to that is “fair enough” but this is why I do it differently.

You pretty well have it Pegged Shadrach.

Very little oil flow an zero Circulation.

When a Prop is screwed on the first time after O/H or New, the oils that is pumped into the cylinder at that time, will be the same oil that’s in the cylinder when the propeller is taken off next. The grey gunk is nothing more than the solids out of the oil that is not circulating.

That being said, the ol wives tale of warming up the oil in the Prop is just that.

Its a very simple system not so different than a single acting hydraulic setup on a Bush Hog.

In the video below, you can see there is only around 20 Degrees of movement from Low/High pitch.

Very little flow.

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19 minutes ago, Cody Stallings said:

You pretty well have it Pegged Shadrach.

Very little oil flow an zero Circulation.

When a Prop is screwed on the first time after O/H or New, the oils that is pumped into the cylinder at that time, will be the same oil that’s in the cylinder when the propeller is taken off next. The grey gunk is nothing more than the solids out of the oil that is not circulating.

That being said, the ol wives tale of warming up the oil in the Prop is just that.

Its a very simple system not so different than a single acting hydraulic setup on a Bush Hog.

In the video below, you can see there is only around 20 Degrees of movement from Low/High pitch.

Very little flow.

Thanks Cody, the information is much appreciated!

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27 minutes ago, Cody Stallings said:

If your looking for circulation of oil, you have to look towards the Reverseing Feathering Turboprops.

they have 90+ degrees of travel an that kinda movement requires lots of oil movement.

Do you have any idea why Greg sees an oil temperature drop when he cycles the props of a TSIO520? Do you see a drop when you cycle the prop of the 520 on your rocket? He says they all do that.

 

3 hours ago, gsengle said:

 


TSIO-540VB I believe, three bladed full feathering. They all behave that way. It’s noticed because it can take me right out of the green and delay departure until the temp comes back up.


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I was terribly confused for a moment given that a 540 is a Lycoming product and that TSIO is typically a Continental. I was further confused by the fact that you’re an Ovation owner (IO550). I now realize that you are likely referring to the TSIO520s on the C402s that you fly for work. 

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Shadrach I have no clue why there is a oil temp drop.

Unless the temp prob is right next to the Gov on a 520, then I couldn’t see where it would catch any colder oil. I haven’t paid close enough attention where the sending unit is on a Continental, As I have not spent enough time under the hood on this plane as I did with my F model.

 

With my 520 I don’t notice it at all, what I do notice is when I let it warm to 125-130 ish at 1000-1100 rpms, when I advance the power to say 13-1400 to get moving I will see a slight drop in Oil Temp when it’s really cold, just a couple degrees says the JPI. But nothing noticeable on the factory Needle.

I have been told by a very reputable engine shop the reason is when it is cold an the top couple of inches of oil in the sump is Luke warm an circulating, any advance in power pulls some of the colder oil up the oil pump pickup tube sending it into the engine showing the drop in temp.

Who knows.

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I was terribly confused for a moment given that a 540 is a Lycoming product and that TSIO is typically a Continental. I was further confused by the fact that you’re an Ovation owner (IO550). I now realize that you are likely referring to the TSIO520s on the C402s that you fly for work. 


Apologies, Continental TSIO-520-VB.


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39 minutes ago, gsengle said:

Also only of note in sub zero temps


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 OK that would’ve been helpful at the outset. I could make a number of guesses as to why the oil temp probe might temporarily be exposed to cooler oil in subzero temperatures. Without seeing a detailed schematic of the oil system of the engine in question, I won’t speculate. However, I’m certain there’s a logical explanation. I am also certain that it has nothing to do with the chilled oil presently in the prop hub (see Cody’s response).

I see we both have an affinity for Latin. Post hoc, ergo proptor hoc seems to apply here. ;):)

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