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Water in Fuel Tank

Beejer

Member
Just bought my RV6A and flew it up to NY at the end of September. Didn’t negotiate the NYC ATC great but made it through without breaking any rules or pissing off too many controllers (maybe one was a little annoyed). Realized the need to modernize the cockpit IMMEDIATELY to help with situational awareness in the NYC area and ordered a new panel. Wife got a big promotion and had to go to Japan (bummer, I know) so we spent most of October there.

Unfortunately there are NO hangers in NYC area and I didn’t have a cover for the plane (cover my fault obviously, dumb). Got back last Wednesday and immediately went to the check on the bird and start the work and found the cockpit completely saturated with rain. Every piece of carpet was waterlogged and ruined. Removed all of that and checked deeper. Found about an inch of water sitting in the elevator tunnel (accessed it behind the seats). Got out as much as I could and left it open to dry out.

Then dread set in and I went to check the fuel tanks. Sumped the right tank. No issue. Relief. No water. Sumped the left tank. Relief. Pause. Fuel is clear but has no color. Panic. Dump. Smell. Sump again. Clear. No smell. Pulled 5 testers of “fuel” out. No smell, no color. 6th one finally had the dreaded fuel water separation. Pulled 3 more and finally had clear fuel.

So the question is… where did the water come from? Can it get from the cockpit into the tank?! How did it get into the cockpit (small gap to be fixed where the canopy meets the back window but there is enough overlap the water would have to blow in horizontally)? How did it get in the tank? Tank has a good cap and o-ring. Airplane was fueled on a rainy day but how long would someone have to leave the cap open to get a cup of water in the tank? Since it’s been sumped clear, does anything else need to be done? Drain tanks? Drain tanks and mechanic? Ground test for an hour or so? Any advice would be helpful. Very nervous about flying the bird now. NYC is a big place with very few places to put down that don’t suck for the occupants.
 
You are smart to be concerned. Please don't end up on one of those Youtube crash analysis videos.

Standard fuel caps seem to allow water in under some circumstances. If you are going to park outside, I'd recommend a bit of tape to cover them. Some kind of plastic tape that doesn't stick very firmly and won't rip off your paint.

Fuel injection or carb?

Sounds like a nice ground run is in your future in either case. I'd really give it a good 15 mins or so of running at a minimum, park it while you have lunch, and then come back and sump again. Sometimes water can get caught in other places in the tank, and then work its way to the fuel pickup. I'd also do some serious wing rocking, let it settle, and then sump both wings again.
 
Sump both tanks to remove all water. Don’t disturb /slosh before sumping tanks, crank and run till oil temp comes up to near 100. Advance throttle, no stumble…u are good. Search here on how to tighten fuel caps, should be slightly snug on removal. Fuel got in around caps most likely.

Cockpit water…slider or tip up? Tip ups known to be more likely to let water in. Close slips of paper around perimeter, close canopy, pull on paper looking for large gaps. U can climb in and have light/rain like water sprayed on perimeter of canopy looking for leaks. For temp fix on gas caps, cover with tape. Good luck
 
Only way for water to get into the tanks is via the fuel cap. Check to see if O rings are not damaged and making a tight seal. Adjusting nut on bottom of cap will increase pressure on O ring. Tip up or slider? Water ingress is a problem with all tip ups, whether through forward hinge point or roll bar. Check your avionics for water damage. Slider will also leak at canopy opening, especially on "A" models. Suggest investing in a good canopy cover that will protect all canopy openings, also belly drain holes at appropriate locations. I have seen several methods to cover fuel tank filler necks including rubber suction cups, Saran wrap etc:.
Unfortunatley hanger space here in the Northeast is few and far between and can run $1,000/month. Sounds like you are in NYC, check satellite airports and get on a waiting list.
Good Luck!
 
The caps have o-rings in two places: The big one you see around the perimeter, and a small one on the stem for the lever. Replace them both and adjust the cap compression to be sure it seals. Keep both o-rings lubricated.

I have found most covers to not be waterproof. I treat them often with a fabric waterproofing spray.
 
Does your plane have a gascolator? If so, open it up & check for water & corrosion. If you have in line fuel filters, if you can open them up, also check them for same.
If you found corrosion in either of those spots, replace those components. Further checks are now appropriate- fuel valve, fuel pump inlet ports in the carb or FI servo may also have corrosion.
I had a F-1 Rocket come in with all these conditions, it flew well… till one day it didn’t…. I replaced his WHOLE fuel circuit.

Water accumulation- you now know where to drill 1/8” holes in the bottom skin for drainage.
Drain holes are a requirement for Canadian planes to pass their final inspection.

Some fuel lids leak. Temperature variations & expansion can actually cause the water on the wing to be sucked in. Maybe cap can be adjusted, or upgrade to one of the lockable caps out there.

If tip up canopy, research VAF for ways others have installed shields or ‘umbrellas’ to protect expensive electronics from water damage.
Tip up or slider, either way a good canopy cover is a good idea.

Don’t forget to get plugs for all other openings- cowl air openings, pitot, etc. Make sure all covers are flagged.
 
THIS........

The caps have o-rings in two places: The big one you see around the perimeter, and a small one on the stem for the lever. Replace them both and adjust the cap compression to be sure it seals. Keep both o-rings lubricated.
I have found most covers to not be waterproof. I treat them often with a fabric waterproofing spray.

The smaller "O" ring is the one most often missed and therefore usually the one that leaks.
 
Usher Fuel Caps


Adjustment instructions and parts shown below. Instead of fuel lube for lubrication, many, including me, use Krytox GPL 205 grease with good results. Expensive, but the small 0.5 ounce tube will last a long time.

i-CZCx5NV-L.jpg


Parts are available from Van's:

 
Thanks as always…

Community continues to be amazing. Now I have some work to do. Will check the caps and check to see that the new canopy cover and cowl plugs are doing their job being waterproof.

How far down that tunnel do you need to put the drain holes?

Any need to disassemble the fuel system if that run-up check and sloshing regime come through clean?
 
Lots of good advice here about the fuel caps. They're kind of tricky to adjust properly, but a properly adjusted cap with lubricated O-rings will keep water out and fuel in. Assuming the tanks were made per the plans, they should allow water to drain out of the low spot on each rib. You shouldn't have to disassemble anything to get the water out. If you can't sleep at night with the thought of water in there, pull the quick-drain sump and drain the tanks. Rock the tail, rock the wings, and stop when they run empty. But again, that's only if you feel the need.

Regarding the cabin, a good quality cover should certainly help until you can get a hangar. Until then, I'd tape up every single joint on the canopy when it sits outside. I use a 3M no-residue duct tape when I'm washing the plane. It does a good job of keeping the water out, not lifting when it's wet, and it comes off clean without pulling paint up. Don't forget the vents can let water in, too. They can even puddle up in the flex hose, giving you a surprise shower the first time you open them in flight.
 
One of the largest sources of water in the floorboards of a -6A is water draining off of the fuselage (the over-wing area) and off of the wings, then down through the wing roots and into the fuselage. The way the bottom fuselage skins and the side fuselage skins join (and the protruding edge of the bottom fuse skin) funnels water into the belly of the aircraft.

You can pull the wing root fairings and seal (proseal would be appropriate) the joint where the bottom fuselage skins make a 90' angle with the side skins. That'll keep most of the water out of the belly of your airplane.
 
Get some Krytox 205.

For short term just oil or grease the cap o-rings, but longer term get Krytox 205 lubricant. It is the only lube that will not get dissolved by gasoline. It will stay lubricated so it will always be easy to operate and seal better.
 
made cheap yet effective cap covers

Since your new plane lives outside...
Consider making fuel cap covers.

I bought very flexible 8" bowl covers from a local fancy kitchen supply store.
They even come in red.
Used a majic marker to state "remove before flight".
Once moistened, they are quite useful.

Best bet, fix up your fuel caps as noted previously.

Happy and Safe landings.

Daddyman
 
Remember proper grounding if draining fuel tanks

I think someone briefly mentioned proper grounding if you plan to drain the fuel tanks, but it is worth repeating should you decide to do that. I recall some pretty scary stories/posts, and even some youtube videos of the static discharge adn resulting fire that can happen if you do not properly ground the plane, fuel container, and anything else being used to drain the tanks. Also this is best done outside of the hangar if you have one, but sounds like you do not have to worry about that for now. I think that the type of materials used for draining can also be a factor. Be safe and good luck with your fixes. Great info in this thread!
 
Water gets into fuel tanks typically in three ways:

-- Leakage through fuel caps (poor fit, poor design, and/or inadequate o-rings)
-- Condensation forming inside partially filled tanks
-- Contaminated fuel supply source

If you choose to temporarily cover the fuel caps be sure that the cover is readily visible during preflight and aircraft operation. Also, be sure that you have obvious secondary warnings (e.g., panel stickers, flags, etc.) to remove the covers prior to flight. Personally, I view such covers as problematic.

If you are going to be stored outside get a substantial cockpit cover. Bruce's Custom Covers look good.
 
Followed advice…

Got myself a cover (Bruce as recommended, seems waterproof but will keep checking it), drilled the drain holes in the elevator tunnel (holy **** there was a LOT of water in there, I’m guessing at least 1-2 gallons), drilled out the bottom of the rudder cap (probably another 1/4 gallon in there), and adjusted and lubed the seals on the fuel tank caps. The culprit cap was VERY loose. So loose that when I sloshed the tank (after draining ALL the water) fuel was coming out the top. I wonder if that accounts for the extra gallon burn on the flight home? So hard to figure these things out when you don’t have a NORMAL baseline for how the plane behaves.

But I wanted to thank everyone for all the advice. Would have totally been lost without the community.

Panel is out. Rebuilding that. Addressing squawks. Found out I need to bleed the brakes (could that be the reason for my wandering landings… no practice is what is needed) but found the way to do it on here. Amazing community.

Thanks again. Will hopefully get it back in the air soon!
 
Found out I need to bleed the brakes (could that be the reason for my wandering landings… no practice is what is needed)

Make sure you check the tire pressure if your landings are weird. Have fun bleeding the brakes. Do yourself a favor and get a friend to help.
 
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