An Unintended Lesson

Re: Little shake vs big shake
Well, I'm 6'6 and 300 pounds. Most light singles, a "little shake" from me is enough to slosh everything around, but I see your point. Back and forth plus up and down.

Re: before/after
True. I'm usually in a hanger and keep the tanks full (less condensation), but if we were outside, a good shake in advance would probably be good. We'd find it on the way to the runup area, and it would suck to have water filling the line from the valve to the carb.
 
gkainz said:
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?
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He said after you find water in the sump so I was talking about that scenario.

Whether or not to shake without finding anything -- hmm. Tough call.

Having a hangar sure helps with that decision. ;)

Until you go on the road and park out in the rain. :(
 
jesse said:
Here is a good picture of water that I found in a C150 earlier this year. It's very obvious:
water-in-fuel.jpg
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I wanted to see how the GATS worked (and if it worked) so I added water to 1/4 full of fuel and whaddya know, when poured back the water stayed in the jar. Then when I went back to a "shot glass" (didn't feel like cleaning the GATS that day) using the one that was in the airplane, I started dumping fuel because I had a similar bubble like in the picture above. After about 4 dumps I realized that it was an imperfection in the sample cup (DOH!)
 
If I recall correctly, the wing shaking stuff on Cessnas was supposed to be mainly for models with bladder type fuel cells, not those with tanks built into the structure of the wings (metal tanks). The bladder tanks often develop wrinkles and imperfections in the bladders that trap small bubbles of water in those folds which need to be agitated some to move them to the low points where the sumps are located. Not a necessary thing to do when you have metal tanks, but keeping the tanks full is a good idea IF weight is not an issue for you.
 
dmccormack said:
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!"
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Wow. I'm betting the NTSB would have never figured out the true cause of the accident.
 
Richard said:
I'm suprised some of you haven't seen water in the fuel tester...that your CFI didn't demonstrate this.
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I think my primary flight instructor was one of the best, but he didn't show me this either. Looking back I'm pretty surprised too.

He is a guy who purposely came back from airline world to instruct because he liked it better.
 
TangoWhiskey said:
Wow. I'm betting the NTSB would have never figured out the true cause of the accident.
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Exactly -- after the crash all the water's gone.

"Pilot failed to maintain airspeed resulting in a stall at low altitude."

i wonder if this situation has ever resulted in a crash and the NTSB made the correct conclusion?
 
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Buy a taildragger and gravity will take care of the problem.
 
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