The International Cessna^® 170 Association

This tank drain was seeping, so I replaced it. It looked pretty old, still, I was surprised at what I found upon removal.

Ain't it simply amazing what these airplanes can take when it comes to deferred maintenance?
I'm glad you found it and replaced it. (The reason the old one is so rusted is because of the water that has accumulated from time to time and remained for long periods. I'll bet most folks would never believe this could happen so.)

Thanks for posting the picture so others can see how important it is to inspect and maintain these valves. If the rust continues in such cases, the valve can actually drop it's innards overboard and the tank will completely empty itself. IN flight this can lead to fuel starvation. On the ground it can lead to a hangar fire (and the resultant issues surrounding all the other airplane owners and property owners in the near vicinity. As an example, a few years ago an airplane drained it's fuel into the hangar floor in Conroe and the hangar caught fire. Several airplanes, including some warbirds, were destroyed, as well as the hangar and the business of the hangar-owner.
Good News: No one was killed or seriously injured.
Bad News: The $1-million in liability insurance of the culprit's owner was not nearly enough to cover all the damages.
Moral: Check your fuel valves and turn your master fuel valve OFF whenever you store your airplane.

Dave F

My thanks also for posting this warning on fuel drains. Seeing how bad the drain was, hopefully you are also thinking about checking for water damage and sediment in the carbarator, sediment bowl AND fuel selector valve . Folks have experienced problems in those areas also. Given the damage condition shown on fuel drain and being the cautious type I would check the entire fuel system.

Jim W

gahorn wrote:... If the rust continues in such cases, the valve can actually drop it's innards overboard and the tank will completely empty itself. IN flight this can lead to fuel starvation. ....

In my experience these valves will stop working either frozen from the rust or plugged and won't drain before they ever fall out though apparently that has happened.

I've had these rust up in as little as 6 months from new and wasn't surprised to see the photo to be honest. Seems that little ring that holds it together is steal and rusts rather easily. Plus the use of the valve scrapes the cad plating off the stem and rust starts there. These things apparently do what they are suppose to do and that is sit in the lowest point of the tank where the water will collect.

Regular maintenance of your entire fuel system is a good thing, and perhaps if it hasn't been done routinely it may be time to do it.. But assuming routine maintenance has been accomplished just because this valve is rusted wouldn't cause me to feel the need to tear into the rest of my fuel system.

Aircraft that sit outdoors are especially prone to this sort of thing, as are those that use auto fuel. (Ethanol in autofuel cannot be counted upon to remove water, but it can be counted upon to cause corrosion.)
Jim's suggetion to check the drain on the gascolator and carburetor are good ones. Don't overtighten the pipe-threaded plugs in carbs and fuel valves. Just finger-snug and then 1/16th turn, and safety. (or you'll risk fracturing that expensive carb bowl and valve body. Remember, there's no fuel pressure in these locations, only gravity.)

I always teach my guys to check all the drains on preflight for just the problems that George describes - I always yank on the drain to make sure the guts don't come out and make a big hole. depending on the drain type, there is either a flat seal, o-ring, and/or a roll pin that holds the spring-loaded stem in place, and if something fails it will just shoot on out of there.

Bruce has a good point too, with the type of drains that we normally use on these airplanes they'll jsut rust solid if they're neglected, so when you DO get around to checking it - if it doesn't move then you pretty much can guess your problem.

we also have a problem with our cloudseeding twin Cessnas with breaking the drain stems off (that protrude out of the wing) from hail or graupel, but that's our own special problem that I don't expect you normal folks to experience we always modify the drains so they don't extend too far to help with that problem.

I only bought the airplane two months ago, so I'll be checking the fuel system further. I'll start with the other tank drain, then pull the fuel selector drain plug, then move on to the carburetor. The airplane has lived in CO, UT, and NV since new so I was surprised to find this kind of water damage, but airplanes travel.

To me the big lesson is that even an airplane that appears to be in excellent condition can be hiding dangerous problems.

Update:

Here's the RH drain. Looks like someone wire-brushed off the rust, put on a new seal and reinstalled it. Didn't change the base O-ring, though. Next stop, the fuel selector.

Dave

Found out the hard way that cleaning these with a wire brush is useless. You will wipe off and cad plating preventing rust and it will rust again faster than you think. Like in several weeks.

Can someone tell me if there's a way to inspect the fuel tank outlets and drain (inside the tank) through the filler neck? There's a baffle in the tank that blocks my view aft. How do I inspect the tank interior without pulling the fuel gauge? Is this a job for a borescope?

At about $15. each would it not be good practice to just change them out every couple years ??
Makes for a good opportunity to give the fuel tanks a good flush at the same time.
Just a thought..............

Jimmy M. wrote:At about $15. each would it not be good practice to just change them out every couple years ??....

Hey, great minds think alike!

Now, can someone suggest a way to inspect the inside of the fuel tank?

DaveF wrote:...Now, can someone suggest a way to inspect the inside of the fuel tank?

From the British Aerospace Maintenance/Inspection manual: "The fuel tank interior is to be visually inspected using a torch." (No kidding!)





Definition: Torch: (British) a hand-held lamp, usually battery-powered. (In other words, a flashlight.)

gahorn wrote: Definition: Torch: (British) a hand-held lamp, usually battery-powered. (In other words, a flashlight.)

Awe Gees George....I liked the idea of an oxy-acetylene torch.

Every annual I remove the sump drains. There is water that is below the drain point in the sump drain valves. I have a few spare sump drains valves that I can swap out in a few seconds. Your arm gets wet but you only loose a few oz of fuel when you get good at it. Also if your safety wire hole, in the wing is getting bigger than it should be, epoxy a fat washer on top of the wing skin to so that the safety wire does not cut into the skin any deeper