I've had to start using fuel cans and a Mr. Funnel because of the fuel system being replaced at my airport. After seeing the crap that came out of the bulk tanks, I'll probably continue to use the funnel. 600 gallons of rusty, muddy sludge in an 8,000 gallon tank

hotrod180 wrote:If the cans were totally "clean", there's a good chance the contaminants were introduced to the fuel beforehand. With that in mind, maybe we should all be using a Mr Funnel even when gassing at the airport 100LL pump? I don't see too many people doing that.

Next time you're fueling at your local aerodrome, take a look at the filtration system installed there. Also, chat with whoever inspects and certifies that system regularly.....it happens often, by the way.

Now, check out the filtration system at your local gas station.

Orders of magnitude difference in how a gas is handled. And that is one of the reasons avgas is so expensive.

MTV

At KNOP the airport manager throws $1500 worth of Racor filters into the trash (approved HAZMAT bin) each year that are perfectly clean to keep the certification current. Total waste of Dinero but, the fuel has a continued inspection program. The price reflects it.

I found this old thread about cap replacements for old Cessnas and I thought I would share my story.

I have a Cessna 205 that had the original flush caps. At last annual (May 2016) the A&P insisted we should replace them with either the Cessna or the Monarch cap system. I selected the Monarch system as at $1400 for a set it was less than the $2400 cessna kit and it looked like a better system.

Since installing we have had a recurring issue where if I top the tanks (I have 80g long range tanks) the top 10 (call it $60 per side or $120 per event for both) or so gallons will siphon out of the top of the tank. When it first happened we requested and received a new set of O-rings and the problem seemed to go away for a bit.

As of now, they've been on a total of about 8 months and the problem has come back. I called up Hartwig on the phone and had a longish conversation about the cause. His position is that if the vent tubes (there are two on the 205) are misaligned at all you can get positive or negative pressure in the tank. The Monarch caps have a pressure relief "feature" that he said would activate with between 2.5 and 3.5 PSI of positive pressure in the tanks. He sent over a procedure to adjust the tubes and a cessna article containing the proper dimensions.

The procedure basically consists of getting the tubes set to the factory recommended orientation and making a mark that gives a reference to their position on the strut. The idea is you go do a couple of touch and go's, to presumably get the tanks to whatever pressure they will be at based on the vent tube location, land and then run out to a waiting step ladder and check if there is air sucking or blowing out of your tanks. If its sucking you tweak the vent tube in behind the strut, if its blowing you tweak the vent tube out in 1/32" increments. He recommended leaving the marks on the tubes and adding verification of vent tube alignment to your pre-flight checklist.

We haven't yet accomplished the above procedure but I figure I will give it one last try with these things before I find some salvage Cessna umbrella caps. When I went out and checked the position of my vent tubes with a set of calipers they were mis-aligned, but were even further behind the strut than recommended which has me scratching my head a bit as I would assume that position would be lower pressure than out in the ram air. If you touch your vent tubes they are relatively wobbly due to being held in with just a rubber grommet through a wing skin. They could easily be displaced by someone cleaning the plane or accidentally grabbing one while trying to push on the strut, etc. The thought of that setup ever holding a 1/32" tolerance sounds suspect to me at, best.

If you search youtube you will find a guy with a C180 who put a go-pro on his wing to catalog quite a lot of fuel dumping out of these caps. He switched back to flush caps. I also found a guy with a 182 who had similar problems and spent a couple of $k messing with his vent tubes and finds the problem goes away when he replaces the o-ring seals which he's been having to do about every 6 months or so. Both of those guys sounded upset and said it would just be a matter of time until a fuel exhaustion event and possible crash due to the caps.

For me, so far, I'm in for the original $1400 (plus labor) for installing the caps plus $1-2k of lost fuel and whatever I do from here on out.

Hartwig claimed that the FAA made them install the positive pressure relief (which the cessnas don't have, they both have negative pressure relief i.e. venting). Their low pressure setting combined with the location in a low pressure area of the wing (I estimate that in cruise its about -1PSI at the chord) combined with the finicky setup required of the vent tubes leads me to not trust these things very much at all. You basically have to balance between drawing a vaccuum in the tank and tweaking the vent tubes to get the tank at neutral pressure with limited data.

I'll post back with what I eventually do.

I used these on a later C182B. http://www.fadodge.com/shaw-filler-neck-adapter/

Tim

You might find this on supercub interesting. Here is a link and also what I did by accident. I think Lance still has the caps with a lid and the caps are down in a sump that can fill with rain like I originally had before the Monarchs.
http://www.supercub.org/forum/showthrea ... Vent-Issue

I'll have to tell on myself. About a year ago I flew around for about a half hour with my right Monarch cap off. The tank started out about 3/4ths full and I didn't lose a drop. The little flapper deal did its job. The reason the cap was off was because a gas boy broke the chain about 20 years ago so the cap was totally separate which was a good thing---it didn't bang up my wing when I took off.. I still have an out the top vent too.

qmdv wrote: I used these on a later C182B. http://www.fadodge.com/shaw-filler-neck-adapter/ Tim

Kind of an ingenious solution, but not especially cheap at $630 for the pair including caps.
But a little cheaper than a set of Monarch assemblies for $699.
Looks like way less installation labor too.
The main thing is how well do they work?
Looks like they use standard Cessna vented caps (like mine,under the covers)
which I believe only vent in.
So if the o-rings seal properly they should be fine.

Sorry to hear about your issues 205driver. For what it's worth, I had them on my first 205 with long range tanks without any issues. Loved them so much they were requisite for my next 205, which already had them installed. This one has standard tanks also with no issues.

Good luck. I hope you can get it figured out. Where are you based out of?


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hotrod180 wrote:The main thing is how well do they work?
.

I have these on my 182A. Since the caps are still under the factory door water can't get into the tank unless the drain gets clogged and the gasket of the gas cap fails.

Bonanza Man wrote:

hotrod180 wrote:The main thing is how well do they work?
.

I have these on my 182A. Since the caps are still under the factory door water can't get into the tank unless the drain gets clogged and the gasket of the gas cap fails.

Worked perfect in late 182B. The late 182B did not have a door with the cap below it. The caps were flush. Installation time is 5 minutes a side.