Smell in cockpit

[Wayne Braden]

I'm new to ICS and in March I purchased a 1959 Comanche 180. My dilemma is I have a fuel smell in the cabin when gear goes down. I have read the past posts about the seepage from rubber fuel cells and I have had my mechanic look at all fuel lines, the sump, the fuel selector and everything from the firewall back, about 20 hours of labor. There is no evidence of fuel stains anywhere. I even thought it smelled like some kind of glue or mineral spirits but only smell it in flight. Could this be exhaust gases? This is my first Comanche, but have a lot of experience in 250/260's and never had the smell. My previous airplane was a super Decathlon and even in winter it is well ventilated. I have checked the engine primer and all openings in the firewall and plugged all those that had gaps. I like everyone else would like to keep my expenses to a minimum, which can make a wife think I have a new girlfriend, which is true, well you know what I mean!! Would like some info if anyone has some answers.

Thanks,
Wayne Braden
N6119P

[N3322G]

Wayne,

Welcome to the Comanche Forum - saw this was your first post.

Funny you should mention this as it was just covered in a maintenance seminar by CTPT, Inc. Comanche Pilot Training Program.
The highly experienced Comanche mechanic mentioned that the fuel smell is often first noticed in the pattern or on final as it seems that when the gear comes down it either changes the air flow or angle of attack enough that there is a fuel smell in the cockpit ... ask me how I know. After 43 years with the twin, we seem to have had leaks in most of the common locations.

At some point the fuel leak will become evident - I usually found the ones on the twin close to fuselage under the wing. If the tops of tanks have dried out, fuel leaks can happen under the fuel bladder top access panel. The right main is usually the first to go as the black wing walk keeps the bladder hotter than the other tanks - learned that from the CTPT, Inc. pilot training.

Of course, can't promise this is the issue especially since I don't fly a 180 but if those are original tanks or repaired original tanks, that would be my guess. If the 180 has the same wing inspection/ access long skinny panel that runs on the bottom of the wing next to the fuselage, you might look very closely there. Hope this helps.

Please post the outcome so we can all learn.

[Cliff.Wilewski]

Hi Wayne,
Most likely you have a fuel leak either at from the fuel cells or the fuel valve. As Pat said, it could be from the top of the tanks and may only leak when totally full. I am one of the maintenance advisors for the ICS and I also own a maintenance shop. I have noted that many times you will notice the fuel smell in the flare and right after landing. I believe that under the floor becomes pressurized at this moment and forces the smell into the cockpit. Most times it is a leaking fuel cell, but can be the valve also. If your fuel cells are original, I would change them for sure. We had the same issue reported this last week by a new customer. We opened the fuel cell access plates ( the plate by your fuel cap) and proceeded to push down the fuel cell a bit to see the top and also the date, and it ripped a 4 inch tear in it! This should not happen to a good cell! By the way, the date on it was 1960! They had some great rubber back then! Check your log books and see if the fuel cells have been changed. If not, I would suspect them. If not the cells, you or your mechanic will have to look at all the fuel lines and the valve under the floor. The leak should be evident, although it doesn't take much fuel to make the odor in the cockpit. If you or your mechanic has any further questions, feel free to call me.
Good luck,
Cliff Wilewski
ICS Maintenance Resource Advisor
815-395-0500

[Wayne Braden]

Thanks everyone for your advice. I have checked the fuel valve in fact took up the whole floor. Found cracks in the seat rail attaching points and had those repaired. The fuel cells seem to be the logical answer. Now to look for fuel cells!

Thanks everyone!
Wayne

[tomburke1]

There are a few choices for fuel cells. Floats and Fuel Cells of Memphis is my choice. Aero Tech in California is another good one. I think they both advertise in thre Flyer. I went with F&FC in Memphis and was happy with them. Airparts Inc had a great price when I bought them. The number for airparts in FXE is 954 739-3575. I deal with Keith there. Check to see if they iclude thev installation kit with it. ( new clips, tape and gaskets)

[Daniel Botzer]

We had same problem in our 59 180 Comanche. Had mechanic check all fuel lines and he couldn't find anything. He said it was probably the bladder in the left wing as the level would drop. Zac in the forum said the same thing. We changed out the bladder at annual last week. It had a Feb 1959 date on it, so it had never been changed. Considering it was as old as my wife it didn't look too bad. But we got a new one from F&FC ($864 with shipping) and put it in. Now no fuel smell in cockpit. Fortunately the log books said the right wing bladder was changed not too long ago so we should be good now.