Engine Run Ups

txflyer said:
We have basically the same plane, and I have the long range bladders too.



Have you ever got any water out of yours after a shake?



Mine wing has a more pronounced angle backwards where the water should settle all along the aft bottom of the bladder. My sumps are at the wing root too and I'm assuming all the way aft in the bladder. But if there are ripples in the bladder flooring, or over ribs, I can see where there could be 'traps' outward along the back low points. :confused:
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Not... Yet... :)
 
For the plane in those tests, is the area just below the fuel pickup the best or worst place for water to settle if it's not going to settle at the sump? Would that mean contamination becomes immediately apparent during taxi and run-up rather than after takeoff?
 
Bill Jennings said:
Some would not like to do this, but my old crusty CFI told me if I was in doubt, pour a little fuel on my fingers. It will dry to a white residue and not be oily. Just another way to check for jet A.
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That white residue is fat leached out of your skin. Fat makes the skin flexible so it doesn't crack and let little nasties in. Or tetraethyl lead. 100LL has four times the lead that the old leaded Mogas or 80/87 had. Bad stuff.

Dan
 
I've had mag trouble twice, both after normal run ups. Both were also on the 3rd or 4th lap of TNG practice. Ground check confirms its good for that lift off, but it may not stay that way
 
evapilotaz said:
I was wondering how often to do run ups. Is it every time before take off.
So for Example. I did the run up engine checks before the first take off and everything checks normal. So I come in for a full stop landing and Park the airplane for an a short period of time. Lets say 30 minutes. Should I do a run up again just before take off in this situation. Should I do run ups every time before takeoff?
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Minimum of a mag check and cycle the props.
 
jesse said:
Have you tested this? In my experience water will settle damn quickly in every container I've ever mixed gas and water in.
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It takes a while to make it to the sump though. When you have a big flat bottom, it takes a while for all the little drops of water to come together and settle into the sump. It's not like in a tall narrow container.
 
flyingron said:
Sumping the tanks 5 minutes after fueling is likely to discover NOTHING even if they fillled your tanks with a high concentration of water. It takes quite a while for the water to settle out.
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James331 said:
Sumping RIGHT after a flight or fueling is a waste, as the fuel doesn't have time to settle for a accurate sump.
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Grab a fuel sample, add some water and note how fast it goes to the bottom. You might be wrong here.

I sump after fueling, but I might skip it if it's a post flight fueling.

jesse said:
Have you tested this? In my experience water will settle damn quickly in every container I've ever mixed gas and water in.
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Interesting photos, but I was also wondering about the integrity of the test. Good thing I have 13 sumps :rolleyes2:
 
Jaybird180 said:
Grab a fuel sample, add some water and note how fast it goes to the bottom. You might be wrong here.
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You do realize that it is not quite the same thing, right?

When the water is stirred up/agitated in the truck and pumped into the plane it is suspended in the fuel to an extent. I have never really experimented to determine just how long it takes (likely depends on how much agitation), but the water does not settle to the bottom of the sump as quickly as if you directly pour a slug of water into a jar of fuel.
 
Fearless Tower said:
You do realize that it is not quite the same thing, right?

When the water is stirred up/agitated in the truck and pumped into the plane it is suspended in the fuel to an extent. I have never really experimented to determine just how long it takes (likely depends on how much agitation), but the water does not settle to the bottom of the sump as quickly as if you directly pour a slug of water into a jar of fuel.
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I've done some agitation also, but I hear you.

I think It still settles. If I refuel pre-flight I typically wait to sump until everything else has been looked over, which I figure should be adequate to allow it to settle. No, I have not done adequate testing to be sure, but I also know that an engine can take a little water and there are other safeguards in place in the fuel system.

Thoughts?
 
Jaybird180 said:
I've done some agitation also, but I hear you.

I think It still settles. If I refuel pre-flight I typically wait to sump until everything else has been looked over, which I figure should be adequate to allow it to settle. No, I have not done adequate testing to be sure, but I also know that an engine can take a little water and there are other safeguards in place in the fuel system.

Thoughts?
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The only other water trap is the gascolator (fuel strainer) and it will only hold about three or four ounces of water. Not much. There's a screen at the carb/injector servo inlet that has a really fine mesh that is reluctant to pass water as long as the mesh is wet with fuel, but that screen can get covered with enough water to stop the fuel flow. There are orifices in these systems that can also be small enough to refuse to pass any water in the presence of fuel; the water's surface tension does it.

There are, if I remember right, three or four forms of water possible in the fuel. Free water is the one we're all familiar with, and it will settle out soon enough. Entrained water is in the form of tiny droplets that will stay suspended for a long time, like cloud or fog droplets. There is dissolved water, impossible to see, and pretty much all gasoline will have some of it. And then there are ice crystals, possible in cold weather, that appear like snow in the fuel sample. If there are enough of those, they can clog filters.

Dan
 
Fearless Tower said:
You do realize that it is not quite the same thing, right?

When the water is stirred up/agitated in the truck and pumped into the plane it is suspended in the fuel to an extent. I have never really experimented to determine just how long it takes (likely depends on how much agitation), but the water does not settle to the bottom of the sump as quickly as if you directly pour a slug of water into a jar of fuel.
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Way back the FAA put on one of their presentations on this I caught at LGB and the number I'm remembering they gave was half an hour. The 'moral' behind this presentation was that you should fuel on landing when practicable.
 
Dan Thomas said:
The only other water trap is the gascolator (fuel strainer) and it will only hold about three or four ounces of water. Not much. There's a screen at the carb/injector servo inlet that has a really fine mesh that is reluctant to pass water as long as the mesh is wet with fuel, but that screen can get covered with enough water to stop the fuel flow. There are orifices in these systems that can also be small enough to refuse to pass any water in the presence of fuel; the water's surface tension does it.

There are, if I remember right, three or four forms of water possible in the fuel. Free water is the one we're all familiar with, and it will settle out soon enough. Entrained water is in the form of tiny droplets that will stay suspended for a long time, like cloud or fog droplets. There is dissolved water, impossible to see, and pretty much all gasoline will have some of it. And then there are ice crystals, possible in cold weather, that appear like snow in the fuel sample. If there are enough of those, they can clog filters.

Dan
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Hmmm......so what's the chemical composition of this substance of which you speak?
 
Very unlikely to get water from a fuel truck or even a pump these days. Above ground tanks and required EPA monitoring of below ground tanks pretty much prevent that sort of leak. Fuel trucks are sumped to.

Most water comes from bad caps form airplanes stored outdoors. Can't say I have EVER pulled any serious amount of water from a properly maintained aircraft.

I have had mags fail and plugs load up. Mag checks are quick and easy verification.
 
flyingron said:
Very unlikely to get water from a fuel truck or even a pump these days. Above ground tanks and required EPA monitoring of below ground tanks pretty much prevent that sort of leak. Fuel trucks are sumped to.

Most water comes from bad caps form airplanes stored outdoors. Can't say I have EVER pulled any serious amount of water from a properly maintained aircraft.

I have had mags fail and plugs load up. Mag checks are quick and easy verification.
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Amen, above ground tanks have really helped on the fuel contamination score. Most of the time you'll get water is from your caps/fillers leaking in the rain.
 
What's making my right mag run real rough on first start of the day? I can clear it up enough to take off, but when I land, another mag check and it's perfectly normal. It's gotta be plugs or I hope not a valve?

I lean aggressive on taxi, and whenever I can. I gotta get new mags and plugs.

WTF? :mad2:
 
If I shut down for less than 15 minutes, say, for a bathroom stop, I won't do another runup before departure. If longer than 15 minutes, then I will. Better safe than sorry.
 
txflyer said:
What's making my right mag run real rough on first start of the day? I can clear it up enough to take off, but when I land, another mag check and it's perfectly normal. It's gotta be plugs or I hope not a valve?

I lean aggressive on taxi, and whenever I can. I gotta get new mags and plugs.

WTF? :mad2:
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First off, you have points, so the first place you go is make sure the points setting is still correct. If it's been 200hrs since they were checked, they're probably off. Reset the internal and external timing to where it should be and try again. People tend to forget that points need a lot of service to keep the system in tune.

Next comes plugs/resistors. Always start your diagnostics with the cheapest easiest thing that could be and work towards the most expensive/complex.
 
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Jaybird180 said:
I see nothing about these multiple suspension of water you spoke of.
I all fairness, I was being sarcastic but now I'm open to something that I've never heard of before. Teach me something new.
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There are many things that any of us here have never heard of before. Some of them are enough of a threat to get us killed. It's my opinion that training levels today generally don't teach enough.

http://www.aopa.org/News-and-Video/All-News/2010/July/30/Cessna-tackles-water-contamination-in-avgas

download.aopa.org/epilot/2010/100730cessnasaib.pdf

http://avstop.com/ac/apgeneral/fuelsystemcontamination.html

http://books.google.ca/books?id=LIr...#v=onepage&q=suspended water in avgas&f=false

Dan
 
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Nothing new here and the 2nd link didn't work. I still think the water will collect together given time, which in a 27gal tank shouldn't take that long.
 
Jaybird180 said:
Nothing new here and the 2nd link didn't work. I still think the water will collect together given time, which in a 27gal tank shouldn't take that long.
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The second link is an SAIB that I accessed via the link in the first article.

Entrained water can take some time to settle. Dissolved water can stay dissolved until the fuel gets pretty cold. Most of the water we're concerned with is the stuff we get out of the sump and gascolator, yet I still find corroded gascolator bowls that tell me that water has been left there for a long time, which further suggests that some pilot's aren't concerned with making sure their fuel is clean. And I sometimes find gascolator bowls that are almost impossible to get off to check and clean the screen, which only happens when they've been there for years on end. Cheap annuals, see?

And I regularly find corroded tank sump drain valves, from water left there a long time. Some of it might get in through the caps, but I bet much of it is entrained water that settles out after a flight.

Dan
 
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