Fuel Contamination (New)
- Thread starter SteveC
- Start date
bob loblaw
New Member
When we drain a sump for water and sedement, we basically drain it once unless we see water or sedement in the sample cup. This leads me to my point, there may still be sedement in the tank that didn't show up in the sample. This is why we should never go into the unusable fuel that is in the tanks.
Maybe I need to have a picture drawn, 'cause I don't get it.bob loblaw said:
Let's look at a C-401 I sometimes fly. Two main tanks, two auxillary tanks, and two wing locker tanks. Either the mains or the aux's can feed directly to the engine, the wing locker tanks have to be pumped to the mains in order to use the fuel in them.
When using the fuel from the wing lockers I turn on the transfer pumps which move the fuel to the main tanks. There is no fuel level indicator on the wing lockers, only a pressure switch on the transfer pump. This pressure switch turns on a light in the cockpit when the wing locker tank transfer pump quits creating pressure, indicating that the tank is empty. When the tank has been "run dry", I turn the transfer pump off. How can I possibly do anything other than run the tank dry???
Since I have no choice but to run the wing locker tanks dry, why would it be a problem doing the same thing on the aux tanks if I want to use every drop of usable fuel from them as well? Where is this mysterious sedement (sic) going to be hiding if it isn't coming out the sump on the first pull?
In my opinion the "don't run the tanks dry 'cause you'll get sediment sucked in" is an Old Wives Tale.
FlyOrDie
New Member
bob loblaw said:
I understand the first part of that statement but I'm failing to figure out exactly what you mean on the last. The sediment does not just stay contained within unusable fuel in the tanks. Water and other junk will get trapped on the bottom of various parts of the tank even when you drain the lowest point. I've drained fuel after spins and zero G stuff and my samples are dirty because I must have forced the trapped water to become "unstuck".
bob loblaw
New Member
Why on earth would Cessna, (who isn't the only maufacturer that does this) have unusable fuel figures printed in the POH? What is unusable fuel? Unusable fuel as defined by the Jepp Private Pilot Manual is a small amount of fuel in the tanks that cannot be safely used in flight or drained on the ground. This definition can be found on page 8-31. I didn't make this up or pull it out of my a$$.
FlyOrDie
New Member
bob loblaw said:
Totally agree, but that doesn't mean that the "unusable fuel" is never used. The Seminole has 2 gallons that is unusable. Lets say you pour 2 gallons of water into the tanks and then top them off. You could theoretically take a fuel sample and find no water. So you then hop in the airplane and blast off only to have an engine failure because that "unusable" fuel got used.
bob loblaw
New Member
FlyOrDie said:
I wouldn't bet that you can dump 2 gallons of water into a tank, top it off, and expect to find no water in the fuel sample. I'm sure you know that water is heavier than gas, so the water will be sitting at the lowest point. Since 2 gallons of water is a lot of water, I would bet that you would get all water until the majority of the water is gone. I have flown planes that have spent the night in a heavy downpour and when I first took a fuel sample it was all gas. I gently rocked the wings and there it was, a quarter cup of water.
ComplexHiAv8r
Well-Known Member
jrh said:
Not sure I would agree with that. There are alot of people buying high performance aircraft with little experience (I know a few people that got an SR22 with only like 10-25 hours TT). They have the money for the insurance.
I don't think that you're making it up.bob loblaw said:
The fuel is considered "unusable" because of the tank design. Manufacturers designate some of the fuel "unusable" because that last bit of fuel cannot be realiably drawn uninterrupted from the tank in all flight regimes, therefore cannot be safely used for flight. There is even a FAR relating to "unusable fuel"; FAR Part 23.959 (also in 25.959 for transport aircraft), which reads as follows:
Nothing in there about picking up contaminants, sediment, or water. The only criteria is that the tank must be able to furnish an uninterrupted supply of fuel. Unusable fuel is the extra fuel required to maintain an adequate level to accomplish that mission. If the fuel pickup could become unported by normal maneuvering, additional fuel is designated unusable to ensure a consistent fuel supply to the engine.
Fuel line pickups, when fully submerged, will draw fuel from all around themselves relatively equally. They will pull fuel from above, below, and to both sides, and will be constantly using fuel from the "unusable" portion of the tank all of the time. Using all the available fuel in the tank is no more likely to pick up sediment than at any other time during normal operation.
bob loblaw
New Member
SteveC said:
These are just two of the 29 pages of accidents that were attributed to fuel contamination. I left out the ones that siad water in the fuel. We are flying aircraft that are sometimes 2 decades old or older. Some of the planes we fly had tanks that are currently rusting. This rust finds its way into the fuel and sometimes into the lines. Anyway, 29 pages of fuel contamination accidents and uncle Tom didn't help me run the search
http://ntsb.gov/ntsb/brief.asp?ev_id=20030813X01323&key=1
http://ntsb.gov/ntsb/brief.asp?ev_id=20030123X00098&key=1
bob loblaw
New Member
Whose mother has a brother named Tom?
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Looks like your mother has a brother named Tom.
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Doug Taylor said:Yeah, but my uncle Tommy, whose neighbor is a 737 pilot says...
Looks like your mother has a brother named Tom.
bob loblaw
New Member
Doug Taylor said:
I think I am the one who should have used the sarcasm tag. I see the humor in what you said, that is why I am giving it back too you homie..