Fuel venting

james_layman · Post by **james_layman** » Sat Jan 07, 2006 2:33 am

While training for the commercial PTS flight maneuvers I noted a quanity of fuel venting from the fuel tank vent. The smell was quite pronounced the other day and when we returned the cabin top assembly and fuselage were stained. This never happens with "routine" maneuvers. Is this normal or do I have an undetected problem? Would it help to fly these maneuvers with less than full tanks?

Jim

mrpibb · Post by **mrpibb** » Sat Jan 07, 2006 4:18 am

Let me guess, Lazy eights and or wing overs. One of the reasons why I dont use car gas. What model 170?

blueldr · Post by **blueldr** » Sat Jan 07, 2006 4:31 am

If you get a pronounced fuel ogor in the cabin it is time to inspect the hoses on the cross cabin fuel vent line. This line is right behind the windshield and between the top fusealage skin and the headliner. It runs between the two wing tanks and vents overboard via the goose neck on the top of the cabin. When the fuel tanks are relatively full and the aircraft is nosed down, this vent line will flood with fuel. There are four connector hoses on this line and if they are deteriorated they will leak fuel into the cabin above the headliner and can create a real fire danger. Even a very small leak will cause a very strong fuel odor in the cabin. Inspection is relatively easy by detaching the headliner at the front end and exposing the vent line and the connector hoses.

n3437d · Post by **n3437d** » Sat Jan 07, 2006 5:06 am

The only fuel "ogar" I see is on the receipt I get after topping off. Its the "$/g" ogar.

james_layman · Post by **james_layman** » Sat Jan 07, 2006 12:58 pm

Thanks for the responses. My 170 is a 1949 A model and I have been burning auto fuel. Problem? Ya the manuvers are the Chandelle, Lazy eights etc. I will pull the headliner down and inspect the hose but what about all the fuel on the outside? The gas caps are new and are working normally.

Jim

Post by **Bruce Fenstermacher** » Sat Jan 07, 2006 4:19 pm

Jim
I haven't practiced those maneuvers in my 170 and there for haven't had the issue that you have had. I can see how this would happen with full fuel tanks and even less and wouldn't worry about it if you are sure the fuel is venting out the outside of the aircraft.

You may want to insure that the vent is open to both tanks. One way I can think of to do this is to blow some air in the vent will listening at each fuel cap. This would only prove that the vent is open but not how much but it's a start.

4stripes · Post by **4stripes** » Sat Jan 07, 2006 8:34 pm

As BL said the hose and clamps connecting the tank vent lines do leak after 50+ years of faithful service. Mine did at the 50 year mark, and was only noticed with totally full tanks.
Not too hard to replace yourself.
Cheers Eric

james_layman · Post by **james_layman** » Sat Jan 07, 2006 11:17 pm

Thanks to everyone for the suggestions. The hose are not quite 50 yoa but I will check them and the cap vents. Will also fly Sunday with half fuel and see what happens.

Jim

Walker · Post by **Walker** » Sun Jan 08, 2006 12:35 am

Have you tried co-ordinated maneuvers? Does your ELT go off when you land too?

johneeb · Post by **johneeb** » Sun Jan 08, 2006 12:43 am

Walker wrote:Have you tried co-ordinated maneuvers? Does your ELT go off when you land too?

Mine does, do you have a problem with that

james_layman · Post by **james_layman** » Sun Jan 08, 2006 2:23 am

I just started so the manuvers are pretty poor. I sure got lazy all these years flying S&L! No ELT problems.

Jim

n3437d · Post by **n3437d** » Sun Jan 08, 2006 5:53 pm

I go up routinely, several times a month and do a series of coordinated turns. I also do turns around a point, etc, just to keep the joints excercised. I have not noticed any fuel venting (smells) or loss of fuel. I have found it useful to download my flights from my Garmin onto my Mapsource to see exactly how my profiles went. It is a great "after event' tool.

mrpibb · Post by **mrpibb** » Mon Jan 09, 2006 12:54 am

Today I was flying to fly (don't we all ?) and got engaged by a Cherokee. After a few wing overs and spirals to lose him I didn't notice any odors, I had 1/2 tanks. I later fuel up to full at one of my local airports, on the way back that darn Cherokee was coming straight for me, after a few Min's of using all approved maneuvers

I got a firing solution and had some odor of fuel but dissipated a few moments later as for the remainder of the flight, my coordination has been improving so the fuel odor along with some other odors is less prevalent these days.

Name and adress withheld

blueldr · Post by **blueldr** » Mon Jan 09, 2006 5:13 am

The goose neck vent on top of the cabin is in a low pressure area and if the vent line floods it will suck fuel out of the vent and stain the top of the cabin. Full tanks and a fast, steep approach will almost leave a contrail behind some airplanes.

N170CT · Post by **N170CT** » Tue Jan 10, 2006 2:59 am

Johneeb & Walker,

My NORMAL pre-landing checklist includes switching "OFF" the ELT

. As my old instructor used to say after I landed (as he retrieved his bifocals from the cockpit floor): "Geez Chuck, you sure don't use much runway........just a little bit here and a little bit there!!"

chuck

The International Cessna 170 Association

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