Condensation
During preflight, one of the things you do is drain fuel from all the sump points, and make sure it smells flamable and looks blue. (100 low-lead aviation fuel is dyed blue). Why?
Condensation. Water vapor is in the air around us. The amount of water that can be held depends on the temperature. Once the air chills below that point, the water will condense, turn to fog/cloud, or in some other fashion re-appear into a for we know it as.
Unfortunately, fuel tanks, if not kept topped off, can have a fair amount of air in them. The plane I had today, had 13 out of 40 gallons filled, the rest of the space was air.
I did not find water in the wing drain points (where fuel is stored), but I did get water at the engine fuel drain. Not a huge amount, but some. It looked like a bubble that sinked to the bottom of the fuel sample. I drained and sampled repeatedly until all the water was out, and then I drained a bit more, to be certain.
The plane did run rough for the first moments, but cleared up quickly. More importantly, I didn't feed the water into the system on takeoff.
Otherwise, I might have emulated
this accident in Rancho Murietta. There was a writeup in one of the flight magazines recently, by the instructor who was involved in that accident.
So, for today, I got to see a real life example of what you preflight so dillegently, and, I had ten touch-n-gos that didn't suck. All in all, an interesting but good day.
Why did you not find water at the fuel drains in the wing first? What aircraft were you flying? How often have you detected water in your sump cup?
I'm presuming that the collection was near enough to where fuel is collected at the tanks and leads to the engine; and the heavier water displaced fuel as it sank down. However I've not seen the fuel system with the wing skins removed.
After finding the fuel at the engine sump, I drained fuel until water stopped coming out; I did rock the wings at this point and rechecked all 3 points (this is a 172P). I never once detected water at the wings. I also decided to do a nice healthy long runup. After checking your site, I'll add the rock, tail tip, and recheck the sumps to my checklist.
As to frequency; I've seen it once only, after flying about 90 hours since the start of the year. We typically have dry air when we have large temperature swings; during the rainy season, the temperature swings are fairly minimal.
Jason,
Thank you very much for the quick response...if it were not for the internet
we would never be able to compare notes.
After reading my timeline on my non-commercial research only website you
will understand that no amount of rocking the wings or dipping the tail will
allow you to positively detect the water that is hiding in the Cessna
highwing aircraft. How would you rock the wings and dip the tail of a Cessna
floatplane?
I did not see one drop of water in my sump cup for seventeen years. Not
seeing any water in my cup for that long lead to be believe that I had no
water in my Cessna 172P integral fuel tank equipped aircraft. One rough
running engine and three total in flight engine failures later did I
understand that not seeing water in the cup actually meant the integral fuel
tank was hiding the water. So I installed four additional drains per wing
per a Cessna service bulletin. With the FAA present for a water test we
poured 52 ounces of red dyed water into both of my integral fuel tanks. With
102 ounces of water in the fuel tanks we did not see one drop of it at any
of the ten sump drains. Need I say more? Not only did the members that make
up the integral fuel tank like the spar and hat-channels damn the water from
ever reaching any of the ten sump drains the sump drains are not actually on
tank bottom. The drains are anywhere from an eighth to a quarter of an inch
above tank bottom. The safety recommendations 99.283 and 99.284 generated by
the 102 ounce water test on my aircraft resulted in Cessna big wigs flying
to Kansas City after the FAA closed the plant for one day and the matter
disappeared. My FOIA request for what happened in that meeting was returned
redacted and that Cessna tests were proprietary.
Again thank you for your response.
Best Regards,
Robert E. Scovill, Jr.
http://sumpthis.com/
----- Original Message -----
From: "Jason Fesler"
To:
Sent: Friday, October 13, 2006 11:41 AM
Subject: Re: [Garbage In, Garbage Out] New Comment Posted to 'Condensation'
> Why did you not find water at the fuel drains in the wing first? What
> aircraft were you flying? How often have you detected water in your sump
> cup?
I'm presuming that the collection was near enough to where fuel is
collected at the tanks and leads to the engine; and the heavier water
displaced fuel as it sank down. However I've not seen the fuel system with
the wing skins removed.
After finding the fuel at the engine sump, I drained fuel until water
stopped coming out; I did rock the wings at this point and rechecked all 3
points (this is a 172P). I never once detected water at the wings. I also
decided to do a nice healthy long runup. After checking your site, I'll
add the rock, tail tip, and recheck the sumps to my checklist.
As to frequency; I've seen it once only, after flying about 90 hours since
the start of the year. We typically have dry air when we have large
temperature swings; during the rainy season, the temperature swings are
fairly minimal.
---
Jason Fesler, http://gigo.com/resume.html
"Give a man fire, and he'll be warm for a day;
set a man on fire, and he'll be warm for the rest of his life."