water in AVgas compared to regular gasoline?

[The motor guy]

I've noticed airplanes have sumps where you can regularly drain the water out. My boat will have the same load of gasoline for sometimes 6 months or more (holds 118 gallons) and i've never noticed a drop of water in it. Then again AVgas is actually pure gasoline, where regular gas has 10 percent ethanol, so I'd imagine it soaks up any water that's in it and doesn't allow it to settle? Must be horrible for these HPDI marine engines. Anyways, back when we actually had pure gasoline, were you actually able to drain water out? I recently read about a small plane that had to make an emergency landing on the beach here locally and the pilot claims he had old fuel with water in it as the reason for the landing. This is what inspired my question here. So what's the deal with airplanes getting water and not anything else? Or is it just a precaution thing, where one rarely would ever get water unless it's a bad seal or something on the aircraft itself?

 

[oldhp]

My guess is the wide temperature swings that that tanks in the wings see.

 

[The motor guy]

My guess is the wide temperature swings that that tanks in the wings see.

Why is it cold up where they fly? Those little planes don't go that high.

Update: I guess so, apparently temperate drops as the air thins. I learned something new here lol

 

[y_p_w]

Why is it cold up where they fly? Those little planes don't go that high.

Update: I guess so, apparently temperate drops as the air thins. I learned something new here lol

Sure. I've been at higher elevations. Try being in Maui wearing a tank top and shorts. Found myself at 7000 feet at Haleakala and it was somewhat chilly. Then it was near 10,000 feet and it was actually quite cold. But I wouldn't think it's necessarily going to be freezing, but certainly that could mean a fairly rapid temperature swing causing condensation.

 

[The motor guy]

Sure. I've been at higher elevations. Try being in Maui wearing a tank top and shorts. Found myself at 7000 feet at Haleakala and it was somewhat chilly. Then it was near 10,000 feet and it was actually quite cold. But I wouldn't think it's necessarily going to be freezing, but certainly that could mean a fairly rapid temperature swing causing condensation.

The condensation won't happen until you get back on the ground though. Eg a cold wing hitting the warmer air when on the ground, so it won't be an issue until the next time you fly. I'm assuming it's cumulative though. May take a few times. Kind of like a cold beer sweating on a hot day. You don't see a cup of hot chocolate sweating on a cold day, or ever for that matter.

 

[y_p_w]

The condensation won't happen until you get back on the ground though. Eg a cold wing hitting the warmer air when on the ground, so it won't be an issue until the next time you fly. I'm assuming it's cumulative though. May take a few times. Kind of like a cold beer sweating on a hot day. You don't see a cup of hot chocolate sweating on a cold day, or ever for that matter.

Got it.

As for being in Maui, I was wearing a jacket because I knew it would be cold. But I saw tour buses getting out where most people weren't properly dressed. I wonder if people in GA aircraft are warned about it.

 

[Nuclear_42]

Most aircraft accumulate condensation in the fuel tanks. From little GA planes checked every preflight to a big airline jets being drained on scheduled checks. Not only is a safety deal because nobody wants water in the fuel it’s also prevents bio organisms from growing in the tanks.

 

[The motor guy]

Most aircraft accumulate condensation in the fuel tanks. From little GA planes checked every preflight to a big airlines being drained on a scheduled checks. Not only is a safety deal because nobody wants water in the fuel it’s also preventa bio organisms from growing in the tanks.

I thought only diesel fuel had that issue. Growing algae and bugs and such.

 

[Nuclear_42]

I thought only diesel fuel had that issue. Growing algae and bugs and such.

Basically all jet fuel is pretty much refined kerosene. Big jets are also fuel sampled to check the levels of bio organisms.

 

[The motor guy]

Basically all jet fuel is pretty much refined kerosene. Big jets are also fuel sampled to check the levels of bio organisms.

I always thought av gas was the same as gasoline, just higher octane and no ethanol. Jet fuel is different though, right?

 

[Nuclear_42]

I thought only diesel fuel had that issue. Growing algae and bugs and such.

From my experience maintaining wide body aircraft it’s quite normal to sump a couple gallons of water per wing. It’s performed on a schedule basis not preflight. Some of these aircraft can hold close to 200k lbs of fuel. So a couple gallons of water per wing ain’t a whole lot considering how many days or weeks at a time are flowed in between sumps.

 

[Nuclear_42]

I always thought av gas was the same as gasoline, just higher octane and no ethanol. Jet fuel is different though, right?

That’s correct. Your typical av gas is 100LL octane Low Lead.

 

[dadto2]

The condensation won't happen until you get back on the ground though. Eg a cold wing hitting the warmer air when on the ground, so it won't be an issue until the next time you fly. I'm assuming it's cumulative though. May take a few times. Kind of like a cold beer sweating on a hot day. You don't see a cup of hot chocolate sweating on a cold day, or ever for that matter.

That's true for condensation on the outside of the tank, but inside the tank the moisture precipitates out of the air and settles into the fuel as a liquid as the plane ascends into lower ambient temps.

 

[Just a civilian pilot]

https://safetyfirst.airbus.com/fuel-microbiological-contamination-treatment/

https://www.aerotime.aero/articles/27860-mayday-incident-in-gatwick-engine-stall-report

 

[Slick]

Regarding smaller propeller powered aircraft that use Internal Combustion Engines they will have a sump drain at the low spot in each wing tank and a gascolator (main line strainer and water separator) before fuel is supplied to the engine.

The example I will use is from a fairly common high wing Cessna 182. It had two fuel tanks, one in each wing. Each tank max capacity was 46 gallons of which 44 were specified as "usable" ( I never wanted to test that specification, reserve fuel at landing is your friend).

Before each flight we would check the fuel (in our case 100 low lead fuel dyed blue) at the two wing tanks and the gascolator. It is important to capture the drained fuel in a clear container to verify the color of fuel for correct type, look for any water/fuel separation line - water will be at bottom of tube check container, and smell if by chance your aviation fuel could be mixed with Jet A type Fuels. If you don't see the expected blue fuel color but just clear liquid then likely you have a slug of water greater then your check container volume. Keep draining until all water is out.

The sources of water contamination could be from the fuel supplier, condensation in your tanks from temperature change when parked or elevation changes when flying (standard lapse rate is 3.5 degrees F drop per 1000 foot elevation change), fuel system leaks usually occur around fuel caps from rain/dew when parked outside or when flying in rain, or unlikely sabotage.

Usually we would not see any water in the fuel but sometimes could get a few cc's.

We had one fatal crash at my home airport years ago due to "water in the fuel" shutting the engine off during takeoff climb. Two elderly gentlemen had a classic Cessna 195 that was seldom flown. The engine shut off a few hundred feet elevation from the departure end of the runway and they attempted what is called the "impossible turn" which is trying to make a sharp turn to make it back to the runway. Sadly they aerodynamically stalled the aircraft and impacted the ground. Sadly had they chose to continue straight and execute an off airport landing there was a level open field to make a engine off landing which likely could have been survivable with minor aircraft damage. Every time I taxi by their hangar I am reminded to stay proficient, focused, trained, and know when it is your personal time to call it quits when age/ability comes into play.

 

[The motor guy]

Regarding smaller propeller powered aircraft that use Internal Combustion Engines they will have a sump drain at the low spot in each wing tank and a gascolator (main line strainer and water separator) before fuel is supplied to the engine.

The example I will use is from a fairly common high wing Cessna 182. It had two fuel tanks, one in each wing. Each tank max capacity was 46 gallons of which 44 were specified as "usable" ( I never wanted to test that specification, reserve fuel at landing is your friend).

Before each flight we would check the fuel (in our case 100 low lead fuel dyed blue) at the two wing tanks and the gascolator. It is important to capture the drained fuel in a clear container to verify the color of fuel for correct type, look for any water/fuel separation line - water will be at bottom of tube check container, and smell if by chance your aviation fuel could be mixed with Jet A type Fuels. If you don't see the expected blue fuel color but just clear liquid then likely you have a slug of water greater then your check container volume. Keep draining until all water is out.

The sources of water contamination could be from the fuel supplier, condensation in your tanks from temperature change when parked or elevation changes when flying (standard lapse rate is 3.5 degrees F drop per 1000 foot elevation change), fuel system leaks usually occur around fuel caps from rain/dew when parked outside or when flying in rain, or unlikely sabotage.

Usually we would not see any water in the fuel but sometimes could get a few cc's.

We had one fatal crash at my home airport years ago due to "water in the fuel" shutting the engine off during takeoff climb. Two elderly gentlemen had a classic Cessna 195 that was seldom flown. The engine shut off a few hundred feet elevation from the departure end of the runway and they attempted what is called the "impossible turn" which is trying to make a sharp turn to make it back to the runway. Sadly they aerodynamically stalled the aircraft and impacted the ground. Sadly had they chose to continue straight and execute an off airport landing there was a level open field to make a engine off landing which likely could have been survivable with minor aircraft damage. Every time I taxi by their hangar I am reminded to stay proficient, focused, trained, and know when it is your personal time to call it quits when age/ability comes into play.

Im curious. Is the pickup installed in that sump too, or is it just for water removal and the fuel pickup is placed elsewhere?They have sumps that people install for diesel pickup trucks to keep them from drawing air on the last 1/4 of the tank, but I've heard this is a double edged sword to place the pickup in the same exact low spot that dirt, water and other debris primarily collect, so then the truck ends up sucking up a big gob of water one day causing issues obviously. Personally imo, they should do a better job of designing the tanks so the last few gallons are corralled into a smaller area installed of 4 gallons sloshing back and forth in a huge 5ft long tank..

 

[Cujet]

My plane has two fuel tanks, really L+R wings. There is a sump drain in each wing, configured to drain any water. A bit of dihedral and drilled holes at the bottom of the sump fitting do a good job.

From there, both tanks feed into a single 1 quart container in the belly which also has a sump drain. The engine draws from this, about mid point. Not at the bottom. So maybe the engine won't be affected by small quantities of water.

Then through a fuel filter/gascolator that has a drain cable on it. The drain cable is right by the oil dip stick in the picture, The angled white tube on the back of the engine. An AD requires draining prior to flight. I have never found water here.

100LL Avgas seems not to absorb any water. If there is water in the fuel (very rare) it will show up in the sump jar. The only time I ever had significant water, it came from a fuel truck that was outside in a storm and improperly maintained. The guy pumped in gallons of water. That was quite an ordeal. They did make it right and I went on my way without problems.

 

[Slick]

Im curious. Is the pickup installed in that sump too, or is it just for water removal and the fuel pickup is placed elsewhere?They have sumps that people install for diesel pickup trucks to keep them from drawing air on the last 1/4 of the tank, but I've heard this is a double edged sword to place the pickup in the same exact low spot that dirt, water and other debris primarily collect, so then the truck ends up sucking up a big gob of water one day causing issues obviously. Personally imo, they should do a better job of designing the tanks so the last few gallons are corralled into a smaller area installed of 4 gallons sloshing back and forth in a huge 5ft long tank..

The wing tank drains are at low spot in each tank and the "gascolator" is at the low spot spot for the fuel system before wntering in our case the carb. The gascolator functions as water separator before going into the carb. The caution with any aircraft fuel is with temperature changes from ambient or "laps rate" temperature drop at elevation. The higher you go the colder the Outside Air. So water freezing is also concern for fuel blockage. You waant the water out f the system and not into a larger sump with the pickup higher. Aircraft are climbing, descending, banking, sometimes experiencing negative G forces due to turbulence, aerobatics, or poor operator inputs; so water moving around is not good. Additionally with Jet A type fuels the water to fuel line is a place for microbe growth in warmer conditions. My seldom used diesel generator and tractor get a additative to control the possible microbe growth. It can be a mess plugging filters. the moter guy, hope I answered your question well enough.

Cujet has a nice post above with a picture of his sweet Cessna 177.

Cujet if that picture is your bird it is nice the the Registration Number end in ---77CJ Cant see the rest. My first owned aircraft was between a C177 RG and a Fixed Gear C182. Chose the latter since I was moving up from training with C150, C177, and Piper 140s. The C177 without the wing struts is a great platform for picture taking.

Best regards

 

[Cujet]

My bird. N177CJ, you know why!

 

[pilottravis]

My bird. N177CJ, you know why!

Man, that engine compartment is spotless compared to the rental turds I've flown throughout the years. Clean ship flies faster, or at least I want to think so..