An Unintended Lesson

[dmccormack]

So I meet the student and the airplane his dad owns and ties down outside. He is going to top off fuel at the fuel point.

After helping move the ladder over, etc, I notice something dripping underneath the fuselage.

I reached underneath and feel -- not oily.
Smell it-- definitely not fuel.

It's water.

I lean on the rear fuselage former and watch water drain from the tail.
Lots and lots of water.

I asked my student what he thought would happen if 4-6 gallons of water raced back to the tail on rotation.

He'd been studying Center of Gravity and summed it up succinctly: "It wouldn't be good."

I didn't want to experiment in a relatively underpowered C150 on a warm night with full tanks and two aboard. But 40-50 lbs of weight shifting suddenly and very far aft would have been interesting.

I learned that it's good to check up on things that drip. My student learned the same. And so did the guy on the other side of the fuel island who saw the water pouring out and said, "Well, that's a good lesson not covered in the books!"

 

[Dan Thomas]

So I meet the student and the airplane his dad owns and ties down outside. He is going to top off fuel at the fuel point.

After helping move the ladder over, etc, I notice something dripping underneath the fuselage.

I reached underneath and feel -- not oily.
Smell it-- definitely not fuel.

It's water.

I lean on the rear fuselage former and watch water drain from the tail.
Lots and lots of water.

I asked my student what he thought would happen if 4-6 gallons of water raced back to the tail on rotation.

He'd been studying Center of Gravity and summed it up succinctly: "It wouldn't be good."

I didn't want to experiment in a relatively underpowered C150 on a warm night with full tanks and two aboard. But 40-50 lbs of weight shifting suddenly and very far aft would have been interesting.

I learned that it's good to check up on things that drip. My student learned the same. And so did the guy on the other side of the fuel island who saw the water pouring out and said, "Well, that's a good lesson not covered in the books!"

Drain holes in the belly are plugged with dust and sludge. Not good, because there are control cables and pulleys that run through there. Cables that corrode, pulleys that seize. That airplane needs a good inspection and cleaning.

Dan

 

[dmccormack]

Drain holes in the belly are plugged with dust and sludge. Not good, because there are control cables and pulleys that run through there. Cables that corrode, pulleys that seize. That airplane needs a good inspection and cleaning.

Dan

Absolutely.

But my guess is the severe rains we've had here the last couple of weeks moved every bit of grit, paper, dust, etc into the drain holes.

 

[Jeanie]

Where was all that water coming from?

 

[dmccormack]

Where was all that water coming from?

Lots and lots and lots of rain in SE PA the last few weeks....

 

[Jeanie]

Lots and lots and lots of rain in SE PA the last few weeks....

No, I meant in the plane, where was the water holding?

 

[denverpilot]

If the forward drains are plugged it sits between the hmm... What ate they called? Formers? Not ribs... The round stiffeners in the tail section on the bottom until something tips the airplane aft or accelerates the airplane and it sloshes over.

I bet you didn't get it all out of the tail. Someone needs to clean the belly bad, clear the drain holes, inspect everything under the floor, relubricate pulleys and cables, and keep the airplane clean from now on.

When I'm scrubbing our belly I try to make sure I don't gunk up the drain holes in each section. A toothpick or something small to clear them after the belly is clean is a good idea.

Some antennas also have them. Especially "box" covered antennas for ADF and sometimes on the tips of blade antennas. You have to look.

Another bad one is if the (usually much larger) drain tube under the battery box in tail-mounted batteries gets plugged or blocked and a battery leaks or boils over some acid. Lovely mess. Lots of damage if it all stays inside.

We have some tiny paint blisters behind our battery drain tube that shows it wasn't plugged but someone had a battery spill/boil-over sometime in the early 90s after the paint job, but before our last battery. (Box is cleaned up and in good shape.) Apparently someone had to clean up a mess in the past.

See, lying on your back with gook dripping on you while scrubbing is educational and informative if you look at the belly real hard!

There's drains elsewhere too on most birds.

Dirty rentals often have been plugged up for years. In dry climates, not such a big deal. In wet, hold on to your wallet when the corrosion is found!

 

[ajstoner21]

If the forward drains are plugged it sits between the hmm... What ate they called? Formers? Not ribs... The round stiffeners in the tail section on the bottom until something tips the airplane aft or accelerates the airplane and it sloshes over.

You talking about bulkheads?

 

[Jeanie]

I'm going to look carefully at the underside of the 152 tomorrow ... Course it doesn't rain here so I doubt I'll find anything but I'm gonna look for drain holes

 

[DutchessFlier]

Dirty bellies and a little paint chipping off of the leading edges are all good signs of a plane that's being flown alot!!!

It is good advice to get under the beast every couple of weeks to make sure the drain holes are clear, amazing the gunk that gets stuck in them.

Good catch Dan, oh and BTW, when it has rained alot, like in the past few weeks around here, I make it a habit to sump out 3/4 to a full GATS jar of fuel from each tank just to make sure.

 

[dmccormack]

Good catch Dan, oh and BTW, when it has rained alot, like in the past few weeks around here, I make it a habit to sump out 3/4 to a full GATS jar of fuel from each tank just to make sure.

Ohhh yeah... I've been spoiled with hangared birds.



Oh -- and it's good to show students what water looks like. I was doing IR training before I actually saw what water looked like in the sumped fuel.

 

[Rob Schaffer]

Ohhh yeah... I've been spoiled with hangared birds.



Oh -- and it's good to show students what water looks like. I was doing IR training before I actually saw what water looked like in the sumped fuel.

My instructor on my second lesson wiped some of the morning dew off the elevator into the gatz jar so I could see how it separated and would look. Found water about a year later very quickly because of that lesson.

 

[Jeanie]

When I was a student I added water to the dumped fuel to see what it looked like. Haven't found water in fuel yet for real though.

 

[rpadula]

Can we actually figure it out? What's the station inches at the tail where the water drained? (Might need a measuring tape!) Put 50 lbs there and compute!

 

[dmccormack]

Can we actually figure it out? What's the station inches at the tail where the water drained? (Might need a measuring tape!) Put 50 lbs there and compute!

Probably -- though the tailcone is narrow. Therefore the center of mass of the water would be bit forward.

 

[tonycondon]

Haven't found water in fuel yet for real though.

or anywhere else around Alpine...

 

[Jeanie]

or anywhere else around Alpine...

Yep, pretty much, however I do know one student who sumped some out of an old plane once....

 

[Palmpilot]

...I didn't want to experiment in a relatively underpowered C150 on a warm night with full tanks and two aboard. But 40-50 lbs of weight shifting suddenly and very far aft would have been interesting...

I spent some time tipping a 172 back and forth in Oregon one day to get the water out of the fuselage. IIRC, it took even longer to drain the water out of the fuel tanks. That thing was leaky!

 

[kimberlyanne546]

My instructor on my second lesson wiped some of the morning dew off the elevator into the gatz jar so I could see how it separated and would look. Found water about a year later very quickly because of that lesson.

This sounds like a good idea, and I've always wondered "what I'm looking for."

I think I will try this next time I go on a flight.


Kimberly

 

[Matthew]

This sounds like a good idea, and I've always wondered "what I'm looking for."

I think I will try this next time I go on a flight.


Kimberly

I remember the first time I found water with the fuel tester - there wasn't much doubt that something was wrong.

 

[jesse]

When I was a student I added water to the dumped fuel to see what it looked like. Haven't found water in fuel yet for real though.

This sounds like a good idea, and I've always wondered "what I'm looking for."

I think I will try this next time I go on a flight.


Kimberly

I remember the first time I found water with the fuel tester - there wasn't much doubt that something was wrong.

Here is a good picture of water that I found in a C150 earlier this year. It's very obvious:

 

[kimberlyanne546]

And when you find the water (I only have a tiny shot glass sized cup) - what do you do?

Keep taking samples until no more water is found?

I can't give it to mx to drain since they don't work on weekends so my guess is that I should just cancel my flight.

A friend said she had a solo engine emergency which they later determined was water in the fuel. She circled the airport on her solo cross country until her plane (my rental 152) stopped having RPM issues - then she made sure to climb and be aware of all airports on the way home.

 

[gkainz]

And when you find the water (I only have a tiny shot glass sized cup) - what do you do?

Keep taking samples until no more water is found?

Yep....

 

[tonycondon]

or until no more fuel is found.

we had a 421 with a leaky cap and everytime it flew through rain we would pull several of the sump things full of water out of it.

 

[dmccormack]

or until no more fuel is found.

we had a 421 with a leaky cap and everytime it flew through rain we would pull several of the sump things full of water out of it.

I once sumped a rental C172 that had just come back form a training flight.

Four full GATTS jars and then I saw fuel.

It's not always a bubble in the fuel -- sometimes it's just water.

It's good to look for blue.

 

[kimberlyanne546]

I once sumped a rental C172 that had just come back form a training flight.

Four full GATTS jars and then I saw fuel.

It's not always a bubble in the fuel -- sometimes it's just water.

It's good to look for blue.

I look for blue by holding it up against the white background of my plane's paint. Then I smell it. Perhaps I should try filling it with fuel one day and then water - to see if I can detect the difference in color and smell. It is a very faint light blue after all.

Kimberly

 

[denverpilot]

That's one downside of MoGas STCs... it's all clear...

It'll still separate and you can easily see the line, but you have to look harder for it.

For telling if you got an entire sample cup full of water or fuel, you may have to use your nose. Standing around sniffing your fuel tester will make you look pretty stupid on the ramp, but what the heck...

And of course, if you're testing for Ethanol, you're probably putting some water INTO a sample... before any of the MoGas goes in the plane, but that's another topic. (Note to self: Don't shake so hard. It takes too long to settle out.)

 

[Palmpilot]

IIRC, it took at least half an hour to get uncontaminated fuel samples from the 172 I mentioned in my earlier post.

 

[dmccormack]

IIRC, it took at least half an hour to get uncontaminated fuel samples from the 172 I mentioned in my earlier post.

When that happens I like to do a nice long taxi before takeoff...

 

[dmccormack]

I look for blue by holding it up against the white background of my plane's paint. Then I smell it. Perhaps I should try filling it with fuel one day and then water - to see if I can detect the difference in color and smell. It is a very faint light blue after all.

Kimberly

And it varies...

If I'm uncertain, I dip a finger in. Fast evaporation means it ain't water. The sniff test validates the conclusion.

 

[kimberlyanne546]

And it varies...

If I'm uncertain, I dip a finger in. Fast evaporation means it ain't water. The sniff test validates the conclusion.

Smell my finger?

 

[rpadula]

Smell my finger?

 

[dmccormack]

Smell my finger?

Beats the engine dying 300' AGL 1/2 mile from the runway...

 

[wsuffa]

And when you find the water (I only have a tiny shot glass sized cup) - what do you do?

Keep taking samples until no more water is found?

I can't give it to mx to drain since they don't work on weekends so my guess is that I should just cancel my flight.

A friend said she had a solo engine emergency which they later determined was water in the fuel. She circled the airport on her solo cross country until her plane (my rental 152) stopped having RPM issues - then she made sure to climb and be aware of all airports on the way home.

Sometimes that's not even enough. I sumped 2-3 cups out of my plane one time while on a trip. Seems that fuel guy didn't get the cap on tight (pretty hard to do, but he left it unlatched) and it rained very heavily that night.

Keep sumping until no more fuel bubbles.

Got home and got some more out next trip.

 

[MBDiagMan]

So I meet the student and the airplane his dad owns and ties down outside. He is going to top off fuel at the fuel point.

After helping move the ladder over, etc, I notice something dripping underneath the fuselage.

I reached underneath and feel -- not oily.
Smell it-- definitely not fuel.

It's water.

I lean on the rear fuselage former and watch water drain from the tail.
Lots and lots of water.

I asked my student what he thought would happen if 4-6 gallons of water raced back to the tail on rotation.

He'd been studying Center of Gravity and summed it up succinctly: "It wouldn't be good."

I didn't want to experiment in a relatively underpowered C150 on a warm night with full tanks and two aboard. But 40-50 lbs of weight shifting suddenly and very far aft would have been interesting.

I learned that it's good to check up on things that drip. My student learned the same. And so did the guy on the other side of the fuel island who saw the water pouring out and said, "Well, that's a good lesson not covered in the books!"

And YOU are a wise instructor for looking over the plane well enough to find it.

After I bought my plane, my then new instructor wanted to see my log books before we flew. He then went over the plane as closely as humanly possible without disassembly.

This is an old school airplane/helicopter pilot. He was a helicopter cop among many other flight experiences. He's dealt with 50 years worth of flight emergencies and is still walking around healthy. I took quite a bit away from all this scrutiny since my goal is to be a CFI for my retirement years.

It doesn't sound like a good idea to just go jump in a students plane and go flying.

Doc

 

[dmccormack]

And YOU are a wise instructor for looking over the plane well enough to find it.

After I bought my plane, my then new instructor wanted to see my log books before we flew. He then went over the plane as closely as humanly possible without disassembly.

This is an old school airplane/helicopter pilot. He was a helicopter cop among many other flight experiences. He's dealt with 50 years worth of flight emergencies and is still walking around healthy. I took quite a bit away from all this scrutiny since my goal is to be a CFI for my retirement years.

It doesn't sound like a good idea to just go jump in a students plane and go flying.

Doc

Thank you, but I take no credit. I point you to those fellow pilots and owners who took the time to show me how to own and operate an airplane.

Checklists are nice -- nothing beats experience.

 

[Richard]

I'm suprised some of you haven't seen water in the fuel tester...that your CFI didn't demonstrate this.

As has been mentioned, an entire fuel sample can be full of water. Looking for color, smell, and evaporation are telling.

The most water I ever sumped was 7 GATTS jars from one tank. The lineman had left the cap off the night before. Naturally, it rained all night and morning. I always supervise refueling but in the case of the rental fleet, this kind of stuff happens.

 

[xaminmo]

If you get a sump with water in it, then giving the wing a little shake dislodge a bubble of water towards the pickup tube while still on the ground.

Also, sometimes you get a little water from the pump, depending on where you are.

Waiting a few minutes to re-sump after either is good practice, so the bubbles have time to migrate. Maybe that's why I like planes with a little more dihedral...

 

[denverpilot]

If you get a sump with water in it, then giving the wing a little shake dislodge a bubble of water towards the pickup tube while still on the ground.

Don't know about you, but I'm going for a very big shake. Grab the end of the wing and get some good sloshing noises going.

Let it sit for a bit afterward.

Rubber bladder tank wrinkles can trap a lot of water and a little shake isn't going to get the water over the humps if the tank has developed them.

Acceleration for takeoff and rotation will do an excellent job of moving it to the fuel ports though.

 

[gkainz]

Don't know about you, but I'm going for a very big shake. Grab the end of the wing and get some good sloshing noises going.

Let it sit for a bit afterward.

Rubber bladder tank wrinkles can trap a lot of water and a little shake isn't going to get the water over the humps if the tank has developed them.

Acceleration for takeoff and rotation will do an excellent job of moving it to the fuel ports though.

1st shake before or after 1st sump test? If you did have water sitting in what "is supposed to be" the low points (yeah, I've seen the "cessna tanks" website), you've just agitated it back out of suspension (or is it the other way around?) again, maybe? How long might it take for that water (if any) to settle back into the low points again?