Fuel tank cross venting

[Viking]

I’ve seen some debates over whether or not the fuel tanks should be cross vented, or vented to one another. AC 43.13 says tanks should be cross vented, but the plans don’t call for it. Is this something I should be concerned with? It would be fairly trivial to run a vent line between the tanks, the vents could connect at the top sight glass fitting. Unless anyone has any reasons why it’s a bad idea, I think I’ll add a vent between the tanks. What does everyone think?

[whee]

image.gif
Consider adding a cross flow preventing check valve to your cross vent.

[kestrel]

I suggest, don't bother. The stock system works fine. Unless you cross vent from the outboard end of each tank, full tanks will cross flow when parked on a slope.

[alaskabearhawk]

FWIW, I installed a cross vent in mine between the top outboard corners of each tank. I did a seven-part write up in my kitlog and made a short YouTube video. I figured that it was a good concept, but like you said there has been quite a bit of previous discussion on the forum. The bottom line for me was having the redundancy of an air source for the tank in the rare chance the tiny vent hole in the fuel cap becomes blocked or obstructed. http://www.mykitlog.com/users/displa...=280695&row=20

[Battson]

image.gif

Viking there has already been EXTENSIVE discourse on this subject.

I suggest reviving one of the old threads, if you want to discuss further. There isn't much left to say, which hasn't already been written down.

[Viking]

I decided to skip it. Thanks guys!!

[Lucasdenes]

Hello everyone, I just arrived here and I have a question. If cross ventilation is not necessary, then where do the ventilation lines go? I can't find anything about this in the manual. Should there be one and I can't find it?

[arborite]

The fuel caps are vented. No vent lines.

[Bearhawk Aircraft]

No cross venting is required. In stock configuration, the system will flow evenly from both tanks with valve on both and will require very little fuel management other than transferring aux tanks if equipped.

[alaskabearhawk]

Funny, I was thinking about this just the other day. After returning from a flight, while fueling my BH, I noticed this bug splat on the fuel tank filler neck. That was the first one for me and I even took a picture of it to share with the BH forum to check your fuel caps occasionally for obstructions. About an inch higher and I might have had the opportunity to test out my fuel tank cross-venting!

Bug splat.jpg

[N204jh]

I'm really struggling with the vented fuel caps. I get it that they are so simple and perfect for VFR clear flying days. But folks (like me) are also putting in IFR panels with the expectation that we can fly IMC. Hopefully not icing, but that could happen too unintentionally. But up here in the PNW, I fly in the rain ... a lot. And that vented cap has two strikes against it - it's a rain catcher and the sharp angle makes it an icing magnet.

That's why we use heated pitot tubes and notice ice first on the temp probe. Following my trusty 182 design, I'm going to add a vent overboard on each wing right behind the strut (Cessna manual has it a 1.12" right behind the strut so it doesn't collect bugs nor ice when flying.

Or is there an easier way? Am I overthinking this? Has anyone had an inadvertent icing encounter with no issues with the vented caps?

[Bcone1381]

I'm really struggling with the vented fuel caps. I get it that they are so simple and perfect for VFR clear flying days. But folks (like me) are also putting in IFR panels with the expectation that we can fly IMC. Hopefully not icing, but that could happen too unintentionally. But up here in the PNW, I fly in the rain ... a lot. And that vented cap has two strikes against it - it's a rain catcher and the sharp angle makes it an icing magnet.

That's why we use heated pitot tubes and notice ice first on the temp probe. Following my trusty 182 design, I'm going to add a vent overboard on each wing right behind the strut (Cessna manual has it a 1.12" right behind the strut so it doesn't collect bugs nor ice when flying.

Or is there an easier way? Am I overthinking this? Has anyone had an inadvertent icing encounter with no issues with the vented caps?

Your concern has merit. Your knowledge of winter IFR in the PNW exceeds mine. Our vented caps can't tolerate ice. I'm experienced in flying certified know ice aircraft in the great lakes area. Our vented caps would efficiently collect ice if any icing phenomenon is encountered.

With that being said, I use vented caps as designed with no other venting, thus limit myself to VFR. I wont tolerate ice. Snow is not ice. Clouds often are not ice even below freezing yet if a Bearahwk Pilot has that mindset then it would cause me grave concern. It WOULD bite them some day. So If you wont restrict yourself to flying IFR below 0c then vent the tanks. Added venting is a small cost to add peace of mind and utility to your craft if this concern is going to restrict you. Only you can judge that.

[N204jh]

Thanks, Brooks, for your thoughtful response!

[Untainted123]

But up here in the PNW, I fly in the rain ... a lot.

I think the point about rain being able to enter was discussed somewhere else, with the understanding that surprising little if any rain goes in. I think the theory was that some sort of pressure bubble forms in front of the hole (since air isn't actually flowing into the gas tank), and bugs nor rain ever seem to actually go in the hole and down the tube. I guess it's all anecdotal though, so if you want belt and suspenders, you should do something along the lines you're are talking about.