Why is water in the fuel tanks bad?

[photofly]

Obviously the best answer is to tell the student he's an idiot and send him to another FTU. don't forget to try to withhold his PTR too because he's so stupid. That's the right way to train pilots in Canada.

(Now that I realize I should work harder to develop an inability to suffer fools gladly, I see what great training resource this website is.)

[Colonel Sanders]

Condensation is a negligible source of water in
the tanks. A few years back, a chemist on the
web did a calculation and he thought it would
take between 50 and 100 years to accumulate
significant water in a gas tank due to condensation.

I have personally concluded that water gets into
a fuel tank through the filler neck - either because
it was parked outside in the rain, and it has bad
cap gaskets, or because bad gas with water in
it was pumped into the tanks.

I have been bitten by both. Change the gaskets
in the fuel caps! When they get old, they dry out
and shrink and let water in.

I also have had what looks like snot growing in
the 100LL of more than one aircraft. Yes, 100LL
not Jet-A. Yet another reason to buy Prist every
time with Jet-A.

You don't want to know how I get rid of snot
in the 100LL. There are two different ways I
know of, and the legal beagles here would string
me up by my thumbs if they knew about it.

[Colonel Sanders]

tell the student he's an idiot

You misunderstand. I am frightened by a flight instructor
that doesn't know why water is a bad thing to have in
the fuel. As a commercial pilot, he ought to have a pretty
good idea. I think TK said:

as stupid as the instructor that would talk about dew points, evaporation for an answer

Students get to ask stupid questions which are answered
patiently. Instructors, not so much.

[triplese7en]

Ahh, AvCanada! Self-righteousness at it's best.

For the curious ones, I sure do know why water is not good in the fuel system of an airplane. Maybe me playing devil's advocate wasn't clear enough for you! I hope students don't come and read this thread - I have a feeling it's going to negatively affect some of them because they've had this question, or a similar question, and the reaction from the majority of the experienced instructors on here suggests that this is a completely stupid question to ask. And you complain about flight training in Canada.... get real!

As for the people who think this is a stupid question, can you explain why these two webpages exist?

http://en.wikipedia.org/wiki/Water_inje ... engines%29
http://www.caranddriver.com/features/ca ... n-new-cars

Didn't we just have another thread where MikeGolfEcho explained his frustration at the attitude he received at his flight school? Just to refresh your memory...

The previous occurrence I had asked TWO class 3 instructors (at a different school) to explain something I didn't understand from ground school. Neither were able. One then asked the CFI who was passing by to explain. He berated me for not knowing, and flamboyantly pointed-out that I was nowhere near ready for my written exam.

And then some of the same people on this thread, who berated me/student for apparently not knowing something, wrote in support of MGE and said that's no way to treat a paying customer. The hypocrisy is disgusting!

[Colonel Sanders]

Calm down and read the post above yours, where I said:

Students get to ask stupid questions which are answered
patiently. Instructors, not so much.

Let's say a student asks the question, "I am having difficulty
with my landings". You will get one answer - I would hope
a reasonably helpful one.

Now, let's say an instructor asks the question, "I am having
difficulty with my landings". You will get another answer,
probably less indulgent.

[photofly]

I thought it was a great question. There's already loads of water vapour in the air, which doesn't stop the engine. Why doesn't the little bit of water in the fuel just evaporate along with the fuel? (And thank-you, yes I know the answer.)

[triplese7en]

CS - apparently you haven't been reading the same thread as me. Try reading all the posts where you're not the author and see if you can understand my post!

I didn't call any names out so it's interesting that you're getting defensive...

Photofly - I thought it was a great question as well, which is why I posted it on here hoping for an intellectual discussion about the matter. The answer might seem obvious right away but then someone mentions that water is sometimes injected, on purpose, into the combustion chamber and it might not be so obvious! I'm happy to read that you understand.

[photofly]

Now, let's say an instructor asks the question, "I am having
difficulty with my landings". You will get another answer,
probably less indulgent.

Why? Is the instructor less deserving of help?

It's probably more important to help the instructor, given his influence over many students.

[Colonel Sanders]

Is the instructor less deserving of help?

Many people might wonder why an instructor who
couldn't land an airplane, got his PPL and CPL and
flight instructor rating.

Triple seven: you claim to be an instructor, correct?
Your lack of knowledge of the dangers of water in
the fuel is thus frightening. Your first sentence of
your first post starting this thread:

So a student comes up and asks why water in the fuel tanks is bad

You followed that by a answer that senior pilots
found irrelevant and baffling.

[Beefitarian]

Quit fighting and visit my booth by the BRS guy with the red bird. I'm thinking of showing a continuos loop of plane crashes caused by water contaminated fuel.

Anyone have a link to one with, "Sput Sput Sput, neeeeeaaarr, KABOOM!" Sounds in it?

[triplese7en]

CS - Just in case you thought you were the golden boy...

I can't believe anyone asked this question. How about
I ask the question, "Why is it bad to go to prison?"

Great stuff! Did you say you were a Class 1?

You followed that by a answer that senior pilots
found irrelevant and baffling.

I have to put my uniform on and go fly. I'll reply to that later.

[Colonel Sanders]

Triple seven: you had your silly question answered
in great detail. How about you answer my silly
question now:

"Why is it bad to go to prison?"

Anyways. This is Canada. Canadians know that water
freezes and becomes solid when it gets cold. Did you
know that? As an instructor, I hope you did.

When water in the fuel lines freezes, the engine quits.
Did you know that? As an instructor, I hope you did.

Freezing temperatures are easily encountered even
in summer. Did you know that? As an instructor, I
hope you did.

[photofly]

Is the instructor less deserving of help?

Many people might wonder why an instructor who
couldn't land an airplane, got his PPL and CPL and
flight instructor rating.

I would too, but I'd still try to help. I think you would help too.

You followed that by a answer that senior pilots
found irrelevant and baffling.

Senior pilots are not a homogeneous group, and anyway I am frequently disappointed at how easy some of them are to baffle. It's not a great criterion.

[fleet16b]

Many many moons ago, yes, but finding real chamois today, would be difficult I think.

They are not on the shelf at the general store or the Walmart super center that wiped out most of those for a 50 mile radius. (The kids still know what a radius is yeah?)

I think one could find a genuine sheep chamois if they put Ina little effort. I might even google it if I don't get distracted. Would I fail another business if I made a fuel strainer with a small piece of chamois in it to separate water. If it gets to the lower half of my strainer it's fuel. If it's trapped on top, it's water.

Come visit my booth at OSH 2014?

Guys
You can buy a funnel at Aircraft Spruce that has a water trapping screen in the bottom of it
Works great

[Colonel Sanders]

I think you would help too

A think I mentioned that a while back, a nice young
guy came to me - he'd failed his class 4 flight instructor
initial flight test. He couldn't keep the ball in the center.

How he got a PPL and CPL and did all his flight instructor
training without learning how to keep the ball in the
center is a question for another time.

Anyways, I took him up, did a couple flights with him,
taught him how to use the rudder pedals using my
usual bag of tricks, and he went home and aced his
class 4 initial.

When people flunk their class 4 initial, it's a huge deal.
They're depressed. Their recommending class 1 - whom
is usually an incompetent knob - is usually furious. The
FTU is embarrassed, and tries to blame the candidate.

What nonsense. The student is merely "moving parts"
between the instructor and the examiner. If the student
fails, that is a direct reflection on the instructor - not the
student.

It's amazing how few people in flight training comprehend
this tiny detail.

I took another failed class 4 as a project, a while back. His
PGI was 22 pages of detail, per exercise. I was horrified.
He did not know how to construct effective PGI. He did
not know how to apply learning factors.

We re-did (groan) all of his PGI. He could use ONE PAGE
(ok, both side) for the each PGI and that was it.

Once he learned to create good PGI, then he had to learn
how to present it (TKT, motivation, questions).

Anyways, he did, and he passed his next attempt, no problem.

I spend a lot of time with a lot of corner cases. You
want to have fun, and get some grey hair at the same
time? Teach a few people to land a blind biplane. And
then teach them to unspin it. Be sure to cover all of
the common modes in the six-pack spin matrix. And,
don't break the crankshaft while you are doing it. Or,
hit the ground.

[photofly]

I think one could find a genuine sheep chamois if they put Ina little effort.

There are lots of uses for chamois leather outside of straining fuel; I used to use the stuff all the time, making pottery.

[Beefitarian]

"Why is it bad to go to prison?"

http://www.brainyquote.com/quotes/quote ... 07094.html

Would I fail another business if I made a fuel strainer with a small piece of chamois in it to separate water. If it gets to the lower half of my strainer it's fuel. If it's trapped on top, it's water.

Come visit my booth at OSH 2014?

Guys
You can buy a funnel at Aircraft Spruce that has a water trapping screen in the bottom of it
Works great

Bologna! Just because it's less than half the price of mine?

Sputter sputter, neeeeeaaaarrrr, KA-BOOM!!

[AirFrame]

What everyone is overlooking here is the obvious point that the photos of the water in the 150 tanks drive home... If the third wheel was at the back where god intended, the water would all sit back around the drain and could be easily removed...

[Chuck Ellsworth]

I thought it was a great question as well, which is why I posted it on here hoping for an intellectual discussion about the matter. The answer might seem obvious right away but then someone mentions that water is sometimes injected, on purpose, into the combustion chamber and it might not be so obvious! I'm happy to read that you understand.

triplese7en are you instructing on an airplane that uses water injection?

[Big Pistons Forever]

3) There is absolutely no point in sampling an aircraft that has just been refueled as it will take 20 to 30 minutes for the water stirred up by the incoming fuel to settle out again. If you have doubts about the fuel then sample it before you put it in the aircraft by sampling the fuel truck or fuel supply tank.

I am aware of this sentence. However, I really doubt it's accuracy. The difference in density between water an fuel is quite big. Fuelling does not create huge currents, only a little turbulence in the fuel. Where does these 20 - 30 minutes come from? If you mix some fuel in a bottle, add water to it, you will see that the water goes to the bottom of the bottle almost instantly.

All I can go by is personal experience. Once when instructing on a students own aircraft the student sampled the fuel right after fueling and got a clean sample. The aircraft had been sitting for almost a month since its last flight and there had been quite a bit of rain. So after about a 20 min preflight briefing we went back to the aircraft and on a hunch I got him to re-sample the fuel. The fuel cup was half full of water this time and it took several samples to get clean fuel. On the basis of that experience I feel that a significant amount of time is required for water to settle out after it has been disturbed by the fueling process.

Unfortunately this thread seems to have come off the rails so I would like to return to the original question. What do you as the instructor say when the student asks " Why is water in the fuel tanks bad ?" . My first reaction was to blow off the original poster as just a troll who wants to be a smart ass. But on further reflection I can think of many times ab initio students asks questions where my first reaction was " are you really that stupid ? ".

These questions are usually spontaneously blurted out without the student really giving the question much thought. IMO the best way to deal with these is to redirect the question to a more usefull discussion but remain on topic. So this is how I would answer this question

Me: Well any water in the tank will eventually get fed to the engine. Do you think the engine can run on water ?

Student: Well no

Me: But while we are on the subject when do you think we would most likely get water in the tank ?

Student: I don't know

Me: There are 2 main ways. Leaking fuel caps which will allow rain water to enter the tank, or condensation which forms on the inside of the tank particularly when the tank is nearly empty. So how do we know there is water in the fuel sample? And is water the only thing we are looking for ?

Student: The water will be on the bottom of the sampler there will be a meniscus and then you will see the fuel sitting on top.

Me: Correct but be aware that you could have a full sample cup of water with no fuel in it and think that the fact that there is no meniscus means that the sample is all fuel. That is why you have to make sure you check for the blue colour which can be quite faint. You should also check that there is no crud in the sample, this is serious and could indicate deteriorating seals or other serious problems with the fuel or fuel system. What would you do if the sample was pale yellow ?

Student: Well I remember reading that yellow is the colour of jet fuel. Since I am not flying a jet, Yet , this is not right so I will contact maintenance.

Me: Very good as jet fuel will cause catastrophic detonation and cause the engine to fail. This is a real gotcha because there may be enough avgas in the fuel lines to get you airborne just in time for the engine to blow up thus seriously ruining your day.

[Shiny Side Up]

Canadians know that water
freezes and becomes solid when it gets cold. Did you
know that? As an instructor, I hope you did.

When water in the fuel lines freezes, the engine quits.
Did you know that? As an instructor, I hope you did.

Freezing temperatures are easily encountered even
in summer. Did you know that? As an instructor, I
hope you did.

One would hope that people would catch on to these things by just being alive. I have long ceased to be that optimistic about the human race.

I got asked once what side of the airplane was the right fuel tank on. You do one of these because you can't tell if they're putting you on.

[5x5]

I got asked once what side of the airplane was the right fuel tank on.

Don't be quite so quick to assume this is a stupid question. Without knowing how long the person asking the question had been around airplanes, it's not that silly.

If they're quite new, what direction are they facing when checking the tanks? Typically towards the tail. If they haven't been around enough to know that the reference left or right is always facing towards the front of the airplane it's easy to see why they would be confused by a reference to the right tank. After all, in their limited experience when looking at the tanks, it's not intuitive that the right one is the one on the left.

[AirFrame]

Once when instructing on a students own aircraft the student sampled the fuel right after fueling and got a clean sample... So after about a 20 min preflight briefing we went back to the aircraft and on a hunch I got him to re-sample the fuel.

Just a thought: What happened between the first sampling, and the second sampling? Was the plane left, unmoved, at the fuel dock? (Aside: If it was, then that was a good time for a lesson on airmanship...)

If not, I think the photos on the Sump This website make it quite clear that moving an airplane around at all could dislodge a fair bit of water... I rock my wings during my walkaround, and sump the tanks last, just in case there's any water trapped that might dislodge later.

If you free the water up from it's "hiding" place, it'll flow quite quickly along the bottom of the tank to the next lowest point. The risk is that it's not "free" to move. Waiting without agitating the system won't change the fact that water has inertia... If it's not moving, it isn't going to start moving without an external input.

[Shiny Side Up]

Don't be quite so quick to assume this is a stupid question. Without knowing how long the person asking the question had been around airplanes, it's not that silly.

If they're quite new, what direction are they facing when checking the tanks? Typically towards the tail. If they haven't been around enough to know that the reference left or right is always facing towards the front of the airplane it's easy to see why they would be confused by a reference to the right tank. After all, in their limited experience when looking at the tanks, it's not intuitive that the right one is the one on the left.

[Taco Joe]

Water can cause double engine failures...happened to myself and several other crews last summer in Schefferville. A good reason to always check your fuel.