Today's Message Index:
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1. 12:48 PM - Tank Vent/Newton Fuel Caps (dmaib@me.com)
2. 07:35 PM - Re: Tank Vent/Newton Fuel Caps (Bob Turner)
3. 07:50 PM - Re: Tank Vent/Newton Fuel Caps (dmaib@me.com)
Message 1
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| Subject: | Tank Vent/Newton Fuel Caps |
I have been living with this problem for quite a while and would like to solicit
some ideas for dealing with the problem.
I purchased and installed the retrofit locking caps that Van's sells for tanks that are already built. http://tinyurl.com/7fbvpyw You receive a sleeve that fits into the existing fuel cap flange. You install this sleeve into the flange using tank sealant to secure it, and then the new caps fit into the sleeve. Easy job and it looks great. The caps are manufactured by Newton and are very nice. The problem is that when tanks are filled, the fuel comes into contact with the bottom of the cap (the cap is about 1 1/2 inches deep), and, after takeoff, fuel siphons out of the key slot on the cap until the fuel level drops below the bottom of the cap. Usually, the problem stops quickly if you are burning fuel out of the tank. I also have the SafeAir1 extended range tip tanks and have installed these caps, but they do not have this problem. The tank vents are different on the tip tanks. They are a coiled aluminum tube versus the simple 90 degree bent tube on the main tanks. Both vents have the beveled opening facing forward. Could the difference in the vent lines be the key to solving this?
I was admiring a Harmon Rocket a couple of weeks ago and I noticed that it had
the Newton caps installed. I talked to the owner and he confirmed that they were
the same caps from Van's. He said he fills his to the top routinely and never
has any fuel siphon through the key slot. I did not think to take a look at
his tank vents. I am aware of several RV-10's that have these caps and, as far
as I know, they all have this problem. I emailed Newton about this, but have
received no response so far.
Any thoughts or suggestions, guys/gals? [Question]
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David Maib
RV-10 #40559
Transition Trainer
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=370242#370242
Message 2
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| Subject: | Re: Tank Vent/Newton Fuel Caps |
I don't have these caps but it sounds to me as if there is a design defect, or
perhaps an O ring that needs replacing.
Since the fuel caps are on the top of the wing, a low pressure area, they will
siphon fuel out if they leak at all. This will also make the fuel pump work harder,
especially if the normal vent can't keep up with the pressure loss out the
top. And if gas can get out, then rain can get in.
Fuel caps shouldn't leak.
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Bob Turner
RV-10 QB
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=370262#370262
Message 3
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| Subject: | Re: Tank Vent/Newton Fuel Caps |
Bob Turner wrote:
> I don't have these caps but it sounds to me as if there is a design defect, or
perhaps an O ring that needs replacing.
>
> Since the fuel caps are on the top of the wing, a low pressure area, they will
siphon fuel out if they leak at all. This will also make the fuel pump work
harder, especially if the normal vent can't keep up with the pressure loss out
the top. And if gas can get out, then rain can get in.
>
> Fuel caps shouldn't leak.
I certainly agree that caps should not leak. But, all of these caps installed on
RV-10's seem to do this. I can't imagine it is an o ring problem when this seems
to be a fleet problem limited to RV-10's. So, I would lean towards the design
defect, except that it does not seem to be a problem on other types of aircraft.
(that I know of)
Interestingly enough, My airplane has had to sit out in significant rain a few
times and I have never had one drop of water in my fuel samples. Ever.
I am zeroing in on the RV-10 tank vent design because I cannot think of anything
else at this point. I hope somebody on the forum has some insight on this issue.
--------
David Maib
RV-10 #40559
Transition Trainer
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=370263#370263
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