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Is the water a killer?

flightlogic

Well Known Member
Patron
Looking for feedback from any RVer's that have had rainwater (or other water) sucked into the carb. in flight.
My question is, if you lose power from water, but have altitude to work with, can switching tanks, boost pump activation and windmilling prop.... clear the water out and start the engine developing power and running again?
I parked in San Diego last week while out of the country and had the FBO fill the tanks. Knowing a rain was coming and not trusting the caps completely, I had them cover the caps with painters tape. (all they had available)
On return, I didn't have a sampler in the plane (my bad) and thought with everything sealed, I was golden.
Flew home two hours and then found 3 oz. of water in the left tank sump. It must have sat below the inlet screen and never was drawn into the gascolator.
Had there been some turbulence, I might have seen a loss of power.
Only one time in 6 years has this happened after a huge rainstorm. I felt roughness and immediately cut power and aborted takeoff. That is when I learned not to trust the caps. (yes, they have fresh O rings and lube)
Interested if wet cylinders ground out the plugs and it just never starts running again???? Thanks for any input.
 
I didn't have a sampler in the plane (my bad) and thought with everything sealed, I was golden.

As an FYI, the water might not be coming through the caps. The moisture in the air at the top of the tank will condense onto the inside top of the tank skin and then fall into the tank at the most inopportune moment...

Good practice, IMHO, if you're parking outside in typically warm wet climates, cold/cool overnights, slosh the fuel a bit, then have a cup of coffee, then SUMP the tanks...
 
I may get banned for this, but if I were in your shoes on that post-downpour preflight, I would not hesitate to depress the sump drain with a finger tip and drain a few ounces of gasoline directly onto the ground to look for water / make sure there was none in the bottom of the tanks.

You probably launch that much climate-destroying VOC into the atmosphere every month just from tank vent vapor loss.

You and the people on earth underneath your flight path are worth it.
 
The caps are adjustable and can be adjusted to be leak free. My 6 sits outside in the elements now and have never found water in the tanks.

larry
 
...
My question is, if you lose power from water, but have altitude to work with, can switching tanks, boost pump activation and windmilling prop.... clear the water out and start the engine developing power and running again?
...
Interested if wet cylinders ground out the plugs and it just never starts running again???? Thanks for any input.
Random input coming, as requested! :)

When the prop is windmilling, liquid from the carb (assuming similar viscosity to fuel) will get sucked into the engine. If I suspected water in the carb, and I had time, I'd open the throttle fully, mixture full rich, and pray. Keep the prop moving, so the air is flowing through the throttle, sucking in the water. Clearly if you can switch tanks, start the boost pump, full rich, etc. do that - just in case the water is only in one tank.

The question about grounded plugs is very interesting, and I can see where that might happen. The trick is to perhaps lean from time to time to dry them, cuz even a lot of fuel could foul them.

Handling water in the fuel system at altitude is an interesting thought exercise, but I'd strongly recommend avoiding the situation by leaving the aircraft in a hangar, covering the caps with good tape, ensuring that they seal reasonably well, sump before moving the aircraft, and if you suspect water at runup, stay on the ground until you're sure that it's only fuel getting sucked into the engine.
 
I know you shouldn’t pour fuel onto the ground but:

If you don’t have a fuel sampler, draining fuel onto concrete you will easily see the difference between fuel and water. Fuel will spread and water will pool in droplets.
 
Velcro

Put a piece of Velcro on the side of a fuel sampler. Also a piece in a convenient, out of the way but EZ to get to spot in the cabin. Saves u from digging in pockets or baggage areas for it. Did this back in phase 1. Use every time and haven’t misplaced it yet.
 
Put a piece of Velcro on the side of a fuel sampler. Also a piece in a convenient, out of the way but EZ to get to spot in the cabin. Saves u from digging in pockets or baggage areas for it. Did this back in phase 1. Use every time and haven’t misplaced it yet.

Previous owner of my airplane did that. Velcro'd this neat little spring-loaded bracket thingy that holds a fuel sampler. Very handy.
 
YUP

Yes, in hindsight... I should have just drained onto the ramp.
When I got home and drained it, I found quite clean water. Surprised that it was not polluted and a bit brown. Have seen that before.
I like the idea of the cup velcroed along a side panel. That way I have no excuse to avoid the inspection. This is the first water I have found in four years. I will be taking the caps off to increase pressure outward on the o-rings.
I suppose the stem o-ring should be replaced now also.
Thanks guys! Appreciate the ideas.
(still wondering if it would re-start after "drowning")
 
Check the caps, replace o-rings. Lube with Krytox only. You can always put a small vinyl tube on the vent and blow (by mouth only) with soapy water on caps to test for leakage.

If you want to know how long it takes water to go through the carb, just shut off the fuel tank selector in flight and count the seconds until the engine quits. That will give some knowledge as to how long it would take to clear a carb full of water.

The engine will fire back up and clear out pretty fast after the supplied (carb) water is cleared. Water from a heavy rain as little/no effect on running.

The massive rains at 2019 OSH left no water in my 7 tanks. It dripped (though the wind skins) onto my roll servo, corroded the rotor and sheared the pin but no water in the fuel.
 
so Bill

So Bill, you hand flew home from Oshkosh !?!?!?

Thanks for the other thoughts. Will be O/H the fuel caps this Saturday.
Of course where I am in Arizona... it won't rain again for another 180 days....
 
So Bill, you hand flew home from Oshkosh !?!?!?

Thanks for the other thoughts. Will be O/H the fuel caps this Saturday.
Of course where I am in Arizona... it won't rain again for another 180 days....

ROTFL

Yes, hand flew (kinda), but there was wandering involved as I was trying to figure out what had just happened. Apparently after shearing - it began to move with its internal torque but had to be trimmed perfectly or it would over come the friction of the sheared pin and release. After figuring that out I still had AP pitch, then I just set AP altitude and used manual aileron (albeit draggy) to maintain course. Not really a challenge, VFR and only 1.2 hrs to home.

It is always interesting departing with a conga line and a hundred planes rolling to a take-off - then hardly seeing a single plane for the remaining flight.
 
nobody?

So, no one has actually run on water and then had the engine recover?
When I got home and sumped it, I only found water in the left tank. What do you suppose the odds are against it coming from the fuel truck, in a slug?
Pretty sure that is a real stretch.
For the engine experts out there, I have a question: If combustion is not happening, but the engine is turning from prop forces... is the cylinder emptied completely on the exhaust stroke?
And a shorted plug, when free of water droplets will begin firing again, correct?
 
I may get banned for this, but if I were in your shoes on that post-downpour preflight, I would not hesitate to depress the sump drain with a finger tip and drain a few ounces of gasoline directly onto the ground to look for water / make sure there was none in the bottom of the tanks.

You probably launch that much climate-destroying VOC into the atmosphere every month just from tank vent vapor loss.

You and the people on earth underneath your flight path are worth it.


OR you could drain the same amount into an empty gatorade bottle you keep in the tool kit for the job. Odds are there will be no water and you can then pour it back into your tank, or take it home and use it in the lawn mower. If there is water you can still pour 80% of the gas back into the tank and turf the rest.
 
Last edited:
Does anybody do this?

you can then pour it back into your tank, or take it home and use it in the lawn mower.
Maybe at your home base but what if you are away from home?

As to engine operations if you ingest water:
Water in the tank is not the same problem as ingesting water (rain) into the carburetor.
In my own experience, rain, even very heavy rain does not seem to affect engine operation.
Getting water from the tank to the engine is another problem where you may get it to the carb and it will settle at the bottom of the bowl and enter the discharge nozzle first before any more fuel will pass through. I agree that keeping the prop windmilling and sucking up all the water is probably your best chance of getting a restart.
As far as the top end of the engine, it all would be very hot and you'd evaporate all of it before water logging any part of the top end.
I wouldn't worry about it at altitude but the most likely scenario when you have water in the tanks is to suck it up on take off and that is where you can't restart.
 
PM received

I got a very nice PM reply. An ACTUAL inflight result. His Lycoming ingested water from the fuel tank but restarted after a few seconds. He had switched to a non polluted tank.
His curious mind (at 11K ft.) decided to switch back to the water mixed tank. It ran rough again, but cleared up with a tank change. This was repeated but showed all similar results.
My take aways are as follows:
1. don't find a reason to not check it.
2. keep O rings adjusted, fresh and lubed
3. change tanks and go full rich with boost.... if roughness detected.
4. Don't have any of this water issue occur during takeoff. No time for a resolution down low.
 
I got a very nice PM reply. An ACTUAL inflight result. His Lycoming ingested water from the fuel tank but restarted after a few seconds. He had switched to a non polluted tank.
His curious mind (at 11K ft.) decided to switch back to the water mixed tank. It ran rough again, but cleared up with a tank change. This was repeated but showed all similar results.
My take aways are as follows:
1. don't find a reason to not check it.
2. keep O rings adjusted, fresh and lubed
3. change tanks and go full rich with boost.... if roughness detected.
4. Don't have any of this water issue occur during takeoff. No time for a resolution down low.

I’ve had water in a carb twice, once was a Rotax 912, the other was a 4 stroke Dirt Bike. Both times the water would NOT stick through the main jet. Seems the water tension inhibited it from going through. Perhaps a Lycoming is different, but I wouldn’t trust it to always clear up.
 
I’ve had water in a carb twice, once was a Rotax 912, the other was a 4 stroke Dirt Bike. Both times the water would NOT stick through the main jet. Seems the water tension inhibited it from going through. Perhaps a Lycoming is different, but I wouldn’t trust it to always clear up.

I believe this scenario is limited to carb's, which rely upon a very limited amount of vacuum to pull fuel through the jets. FI, with it's 25 PSI, should have no problem pushing water through the small orifices. Possible problem at idle, where pressure drops to 2 PSI or less. Probably still enough, but never tested.

Larry
 
Water is very hard to pull through a carb's jet. That's how a carb works--it sucks the fuel up through the jet. Hence, gascolators are used on carb'd engines to hopefully trap the water before it gets to the bowl in the carb. Of course, the gascolators are somewhat small, and only meant to trap a few ounces of water.

An injected engine has the fuel "pushed" at a much higher pressure all the way through the entire fuel system, including the injector nozzles. So, injected engines aren't quite as affected by water in the system, unless of course it's a lot. You still may hear a miss, stumble, or event a complete shutdown if it's a lot of water, but eventually it should get pushed through the system.

The potential for plugging both systems can come from having water in the tanks and getting it drawn into the fuel lines, where it can potentially freeze if you are flying into the freezing levels. If you want to feel how cold the fuel can get sometime, put your hand on the fuel lines by the selector in the cockpit.

Vic
 
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