I have recently purchased a 1959 Comanche and was curious if all Comanches suffer from water in the fuel strainer? 9 out of 10 times I will pull water from the tank during pre flight. The amount ranges from 1/2 teaspoon to several tablespoons. Strangely it happens that when the airplane is hanagared more water is present in the fuel drain. Is this normal? Note it is equipped with tip tanks.

Also there is an air vent underneath the instrument panel that blows hot air on my feet. We have checked the heat and air pulls and they work good. The air blows whether the heat/air are closed. The duct comes from the instrument panel and goes to the air duct by the air filter. It should be cool air not warm air, does the muffler affect the duct air because of its proximity? Have people disabled it in the summer months?

Last the airplane is equipped with two GNS480s and on the 121 band the ELT will interfere with the GPS signal. Another words if I contact ground, when they talk to me GPS signal goes to half, when I transmit back the GPS signal goes away completely. We placed a filter on the ELT, but to no avail? Avionics shop says get a new ELT, problem is spent too much money working on the problem. Any ideas? Thanks for the help I am new to the airplane.

Jack,

Welcome to Comanche shipowner and to the Forum

In terms of water in the fuel. after 42 years of twin operations - 20 with tip tanks - No, water in fuel s not normal. It is recommended that fuel be sumped before the first flight of the day and after the last one. Don't know if singles have the same 50 hour fuel sump area AD or not. Do know that tight fuel caps, good fuel door gaskets, non-leaking fuel bladders and good fuel sumping hygiene and un-watered fuel produce 100% contaminant free fuel sumps for me.

Also know that Miller wet wings will nearly always produce dirty sumps and at times so will Nacelle tanks - tips will rarely (not at all after new caps)

Hope this helps.

Jack, I've only found water in my 250's sump twice in 1500 hrs. First time due to old fuel caps (needed rubber replaced) after sitting out in the rain at an air show. The second time the water came from a fuel truck with a failed go/no go filter. If it were me I'd check my source for fueling and (2) make sure the cap seal rubber is still soft. I've also heard of bladder tanks getting a wrinkle on the bottom that forms a small water dam and then spills a bit over the winkle when flown and shows up in the sump. I've not heard of the Comanche tip tanks producing water when empty, but it's possible I suppose. 40 years ago I put about 500 hrs in a 1959 250 with tip tanks and we only used the tips for long hauls. The plane sat outside much of that time and would be dripping with dew in the morning, but no water in the tanks or sump! If you are washing your new plane allot I'd suspect the thermos caps. Hope you find the problem soon, water in the fuel selector/sump does not do good things to their inner workings. Ray B

Jack,

How much have you flown the 250 since you got it. How many times has it been all over wet. Do you see any fuel stains under the wings or at the wing root? Any idea about the age of the bladders? Assume you have 60 gallon wing capacity plus 30 gallons in wing tanks. Suggest you keep all tanks topped all the time. You may be seeing residual water from time past. Most of us only see water after heavy rain parked or in flight. Cover the tank lids when washing.

Having owned my Comanche for 43 years, much of that time parked outside, I can honestly say I have only had water in the fuel 1 time. That was many years ago when fuel was delivered out of a truck. I have flown in extremely heavy rain and never had fuel contaminated with water. There is no secret. Fuel caps must be in good condition and tight. The gasket around the fuel access door must also be in good condition. The drain from the top of the fuel tank must be open, to allow any water that gets by the access door to drain out. If you can't find the culprit, as a last resort remove the cover that has the access door from the wing, around 20 screws. You will see the fuel quantity sender sitting in a recess. If it is rusted out (which would be a good indication that the drain is clogged), or otherwise not sealed to the plate, water will get into the tank from that location. If any one of those conditions are not met, you're flirting with water in the fuel. Assuming you find nothing amiss, and you are constantly finding water in the fuel, I would begin to suspect the source of the fuel. If you think it may be contaminated fuel from the supplier, I would get some containers and pump fuel into those first. If that's the source, then I'd have a serious talk with the supplier. Good luck with your new to you Comanche. Find the source of your water problem and you'll be a lot happier.

Dave Gitelman

Thanks I will check the fuel sending unit. Very strange that I find the most water when the airplane is hangared. It could be the fuel source, but I am fueling from different areas. I will keep working, but I am happy to know that it is not normal.

I have only been flying since April and have about 25 hours so far. I think the bladders were replaced in early 2000's and I have not noticed any fuel stains. I am wondering if the fuel caps need replacement or the gaskets are bad. I will check both of those. I do see water/moisture around the fuel cap when I open the fuel access panel. Do you think that the access panel needs replacement?

Thanks for all the help wish I could figure out the heat issue as well.
JH

The seal for the access door itself may need to be replaced.

Kristin,

Thanks for mentioning this - I've actually had water get in the aux tanks that way.

PJK

About the hot air issue - if it's ducted the same in your model as in 1966, besides the more obvious duct on the floor, there is another heat opening just under the panel on each side. On mine there is a small handle that rotates a disc to close or open slots. In the summer I close them.

We discovered that we did not have steering boots for the nose gear. The boots prevent hot engine air from getting to the cabin. JH

Usually, those boots are on the firewall side facing the engine compartment. It is also possible to put them on the inside of the cabin area. Doing so increases their life many times, and they still serve the same function. I put them on both sides as you never know when the ones facing the engine compartment will rip or otherwise become compromised. Just a suggestion.

Dave Gitelman