Fuel in AZ 105 degrees

J

Jason608

Pre-takeoff checklist
Joined
Mar 2, 2015
Messages
174
Location
Arizona
Display Name
Display name:
Jason608
So, I’m now living the Tie down life. It may storm Monsoon tonight or late morning so I filled her up. But at 105-110 degrees, is it “bad” to have that much pressure?


Sent from my iPhone using Tapatalk
 
Pressure? Ar the fuel vents blocked or something?
 
the pressure of being in tie down and wanting a hangar? yes, that pressure can definitely get to you.
 
It did not post. The fuel pressure build up. The last time I filled the tanks and checked the level, it poured out because of the pressure.


Sent from my iPhone using Tapatalk
 
If your filling the tanks at that temp,you have to remember that the fuel is much colder if it’s coming out of an underground tank.
 
Jason608 said:
It did not post. The fuel pressure build up. The last time I filled the tanks and checked the level, it poured out because of the pressure.


Sent from my iPhone using Tapatalk
Click to expand...


From where? If it's from the caps, you have a serious problem.
 
Unit74 said:
From where? If it's from the caps, you have a serious problem.
Click to expand...

Not necessarily. The FARs require that the tanks be designed so that there is a minimum of 2% of the tank volume in airspace above the fuel. Some tanks have the neck extending into the tank a little bit so that the fuel will start spilling over if the fueller puts too much fuel in it, but there will be some airspace above the fuel. Others take advantage of the wing dihedral and put the caps inboard so that the outboard end of the tank will still have airspace.

The required airspace is for thermal expansion. Gasoline expands as it gets hotter. If it was underground where it's cool, and the tanks are topped right up and then they sit in the hot sun where they get a lot warmer than the air temperature, it could easily expand enough to run out of the fillers when the caps are removed.
 
Gasoline warmed from 59F to 105F will expand about 2.5%, or about a half gallon for a 20 gal tank. The thermal expansion coefficient is 0.00095/K. For the curious...
 
Timbeck2 said:
:yeahthat:

But then again, why on Earth are you filling the plane up? You didn't say what type but now its just you and a skeleton.
Click to expand...
Why am I filling a plane up? Because some planes have bladders that are highly suggested they get close to filled after a flight so they don't dry out and crack.
 
EdFred said:
Why am I filling a plane up? Because some planes have bladders that are highly suggested they get close to filled after a flight so they don't dry out and crack.
Click to expand...

It was more of an Arizona/high density altitude question than one of fuel bladders. But at this point, nobody knows what were talking about anyway.
 
Lol, this went off the rails. I was just concerned that filling the tanks and with the heat rising the fuel expansion may cause an issue.


Sent from my iPhone using Tapatalk
 
If your fuel system is healthy, there will be no issue (other than fuel coming out of the vents).
 
I didn’t think about the vents. That makes sense, thanks for the help.


Sent from my iPhone using Tapatalk
 
Buying fuel at 105* and flying on a cooler day is cheating yourself. You buy fuel by volume. Gas is bigger in hot weather. It shrinks when the weather cools. Fortunately air expands with temperature more than fuel does. On the flip side, in cold temps, air is dense and our carbs are limited as to how much fuel they provide, so most of us dial our carbs in for cold weather and lean more aggressively in warm weather.
 
Jason608 said:
Lol, this went off the rails. I was just concerned that filling the tanks and with the heat rising the fuel expansion may cause an issue.
Click to expand...

Where are you in AZ?

The fuel will expand; the only issue will be that you paid for a little bit that ran out onto the ramp through the vents. It won't be enough to worry about (IMO) and it won't break anything.

In hot weather I often ask the line guys at airports I've stopped at not to fill above the bottom of the filler neck, for this reason. Sometimes they do; often, they seem to try to get every last drop they can in there anyway. I've come out, ready to go, to find small puddles and still dripping from the vents. Oh well... a few dollars maybe, but not worth hassling anyone about.
 
EdFred said:
Why am I filling a plane up? Because some planes have bladders that are highly suggested they get close to filled after a flight so they don't dry out and crack.
Click to expand...

Wet tanks don’t like the heat either.
 
EdFred said:
Why am I filling a plane up? Because some planes have bladders that are highly suggested they get close to filled after a flight so they don't dry out and crack.
Click to expand...

Yeah it’s for sure good to keep some fuel in them, but by no means do you need to top them off, none of the working planes do that and they do fine.

We get a good spread of temps where I am and out of my 70+ usable gallons I’ll keep the plane between 1/2 to 1/3 full, split between the tanks. I just don’t need to be hauling the extra weight and I really don’t like filing any tank so much that a change in temp causes it to barf up fuel onto my hangar.
 
I never fill my Cessna tanks and the bladders do fine.The notion that bladders dry out isn't correct in my experience. Not unless the rubber is soluable in fuel, and clearly they aren't.

If fuel is dispensed from a source that's cooler than ambient, like from an underground tank? It's goingbto expand. Fill the tank and watch it leak as it warms, or in a sealed container? Watch it puff up. My bulk tank does it, my 5 gallon jugs do it.
 
Yea I live in AZ (KDVT) and I used to fill the Cherokee up to the tippy tippy top cause you can never have too much fuel. I’d come back the next day and some of it seeped out. Stopped filling it that high and problem solved.

If your in AZ you should join the Arizona Breakfast Club. Cherokees only. 172s that identify as Cherokees are allowed as well.
 
You must log in or register to reply here.
Back
Top