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Old 05-31-2021, 03:07 AM
KayS KayS is offline
Join Date: Jul 2009
Location: lake constance
Posts: 404
Default how much dirt in our tanks is ok?

Hi Folks,

have no idea if there's a problem or not. fuel injected RV7 nearing 100 hours with standard tanks sealed with standard proseal and nothing else.

i religiously drain tanks as part of every preflight inspection. never found water, but anyway... what i find everytime is some dirt or debris in the drained fuel. what you see in the picture is the collected amount draining both tanks three or four times. when you look close there are some small dark pieces, some are more bright.

i have the airflow performance fuel pump spaghetti that contains a filter with a quite large filter area and a bypass valve.

i fuel the left tank with AVGAS from the airports pump for mainly takeoff and landing. the right tank gets premium grade fuel from the local gas station for cruise flight. when i fuel the tank from canisters i use a special fuel funnel with fine mesh filter.

is what you see ok or should something be done?

thank you very much in advance for your inputs.
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Old 05-31-2021, 03:47 AM
Robin8er Robin8er is offline
Join Date: Sep 2015
Location: Socal
Posts: 524

Looks like proseal and possibly bits if aluminum from the build. Keep sumping until it's clean before each flight. It will take a while to get it all out. I might even consider unscewing the drain for a few seconds after the plane has been sitting for a few hours. Ideally you'd be getting less debris the more you sump it.

Check your fueling point to see if the nozzle is suspectable to getting dirty. If it is, you need to find a way to ensure it is clean before refueling. Some airports do a better job than others.

If you have a fine filter on the fuel system, make sure you check it. Good chance it's been catching alot of debris.
RV-8 N695RA flying
Working on an RV-4

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Old 05-31-2021, 04:18 AM
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plehrke plehrke is offline
Join Date: Sep 2006
Location: Defiance, MO
Posts: 1,806

Maybe collect samples from each tank into separate jars to determine if the “dirt” is coming from the fuel or process of getting auto gas.
RV-6A - flying 970+ hours
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Old 05-31-2021, 05:54 AM
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rv8ch rv8ch is offline
Join Date: Feb 2005
Location: LSGY
Posts: 4,139

I had stuff like this for several tanks when I started flying, and I'm about 99% sure it was left over crud from the build - even though I thought I really cleaned the tanks. It eventually cleaned itself out after having to remove the drains a few times due to the crud causing drips. Nothing ever got to my filter, it all stayed in the tank or out the drain. I have the very coarse screen fuel pickups in each tank.

If you don't see the amount of dirt or particles diminishing, then perhaps it is the fuel source.

For the avgas pumps, make sure that there is no dirt inside the nozzle before you stick it in the tank - this is not always easy, but thankfully the nozzle where I fuel mostly seems to leave a few milliliters in the nozzle, so I just point it down and some fuel comes out, cleaning the nozzle. Or use your special fuel funnel for the avgas as well. If it's like the one I have, it flows very well.
Mickey Coggins
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Old 05-31-2021, 06:13 AM
KayS KayS is offline
Join Date: Jul 2009
Location: lake constance
Posts: 404

Originally Posted by plehrke View Post
Maybe collect samples from each tank into separate jars to determine if the “dirt” is coming from the fuel or process of getting auto gas.
that's a good idea. will do so to check if there's a difference between mogas and 100LL.
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Old 05-31-2021, 06:17 AM
KayS KayS is offline
Join Date: Jul 2009
Location: lake constance
Posts: 404

Mickey: i do have this thing. should also work at the AVGAS pump.
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Old 05-31-2021, 06:45 AM
BillL BillL is offline
Join Date: Sep 2007
Location: Central IL
Posts: 6,220
Default Just another example . . .

I got roped into being the Secy for a flying club. The drain on one of the 182's was crunchy. I seemed like a small thing, but an experienced (very) pilot stopped by my desk and told me a story, I then convinced the FBO (company store) to investigate. They found several oz of small gravel, nearly 1/2 cup.

Where did it come from? Well, the habit for fueling from a ladder resulted in lowering the nozzle to the concrete, I did it too. If you hang it by the hose think about how it looks. The nozzle scooped a tiny bit of debris every lowering and ended up in the tank.

The FBO was a little embarrassed when I pointed it out how it happened and repaired the concrete cracks and cleaned the debris and added a cap to the nozzle. A southern coastal airport, former USAF base and lots of stuff blowing around.

You have lots of filters and screens, but the most likely issue is some get caught under the drain o-ring and it begins to leak. Mine did.


Last edited by BillL : 05-31-2021 at 06:47 AM.
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Old 05-31-2021, 08:24 AM
pa38112 pa38112 is offline
Join Date: Mar 2008
Location: Clarksboro, NJ
Posts: 1,001

What you are seeing is fairly normal. Having said that, if it gets in an injector it will likely plug it. The filters seem to be doing their thing. Keep an eye on them, and keep flying.
2004 RV6A Flying
2002 RV6A Flying
1978 PA38-112
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Old 05-31-2021, 08:42 AM
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jcarne jcarne is offline
Join Date: Jul 2016
Location: Worland, Wyoming
Posts: 1,927

Normal. I had a small few pieces as well. It will clear up. I am also anal about having a clean fuel nozzle when I fill up so I take a small flashlight and shine it into the nozzle to have a look. Just make sure to do it with the pump off and don't squeeze the trigger as there could still be pressure in the line.
Jereme Carne
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Old 05-31-2021, 10:52 AM
cajunwings cajunwings is offline
Join Date: Jun 2007
Location: new iberia la
Posts: 858
Default Tank Crud

Might be worth the trouble to remove the quick drains and drain a couple gallons from each tank into a clean bucket. The little squirt you get when sumping is good, but the much higher flow with the quick drain removed will move contaminates better. Every 24 months or so I do this on my planes and always see something. All fuel handling precautions apply. Do this outside, ground everything together and to a ground point, fire extinguishers at the ready ect ect

Don Broussard
RV9 Rebuild in Progress
57 Pacer
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