The fill the fuel Conundrum

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drotto

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drotto
As a training pilot, I was wondering how people deal with this issue. The FAA, plane rental people, clubs, etc all recommend that you fill your tanks at the end of every flight. Fine it make perfect sense to me. From a safety standpoint it keeps water out of the system. From a courtesy standpoint, if you will not be the next person using the plane, it is nice to leave it ready to go. I get it. From a practical standpoint where most 4 place planes are really 3 place, and most 6's are really big 4's, what do you do with the actual fuel if filling the seats is more important than filling the tanks?

I go get my rental plane, but a want to take 4 people up ( including me), more than likely 15 to 20 gallons will need to come out of the tanks, if the people are the magic FAA 170 lbs. How do I get that fuel out? Where do I put it?
 
I often fill my airplane to the tabs, which is about 36 gallons. Gives them a bit of breathing room without really affecting range for most of our trips
 
Most rentals will fly enough that the water issue will not be and issue, and personally I don't think its an issue anyway. I think if they fill it up before your rental without you telling them to then they have done you a disservice. I know they are trying to help, but you are right that sometime you just cant take out the fuel.

I don't fill my a/c up until I know what I need to use it for next. Just my 2 cents
 
That is why I have a Siphon hose and 6 - 5 gal gas tanks.
 
This is only a problem for renters. You need to inform the FBO that you will be doing this and "hopefully" they will not fill the tanks prior to your arrival or will put in the amount of fuel you specify. This is normally not an issue with rental trainers but in the real world many aircraft have auxiliary or long range tanks that are there for flexibility, it's not intended by design to always top them all off. This is why many aircraft have tabs. Commercial airliners virtually NEVER fill their tanks. They put on just enough fuel to carry the load through the existing conditions the distance they need to go with the required safety reserve and no more.
 
The FBO here never tops off even the rental aircraft unless I request it prior to my flight(I'll always have them top off if I'm solo in a 152 or just one pax in the 172). They know especially with the 152s that if two people are sitting in it, there might not be the ability to have the tanks full without being overweight.
 
My FBO would normally top the tanks off but if you let them know a couple days in advance that you would need less than full tanks, they would coordinate it accordingly.
 
As already said, coordination is the key. At my school we have a student/CFI combination that requires the tanks be partially full (partially empty?) To aid this, this student/CFI combination flies on the same days and same times every week, so there is a standing order the night before to NOT fill the tanks. Note at our school, the FBO fills the tanks, not the pilots.

Advance coordination is the key.
 
flyingmoose said:
Most rentals will fly enough that the water issue will not be and issue, and personally I don't think its an issue anyway. I think if they fill it up before your rental without you telling them to then they have done you a disservice. I know they are trying to help, but you are right that sometime you just cant take out the fuel.

I don't fill my a/c up until I know what I need to use it for next. Just my 2 cents
Click to expand...
+1 :yes:
 
Where I instruct, the policy of filling up is largely a courtesy to the next renter. If they are doing pattern work, half a tank might be fine, but if they are going cross country they either need to taxi to the self-serve pump or pick up (possibly expensive) fuel en-route. 95% of the time the fill-up policy works well, and you coordinate with whoever has the aircraft before you for other occasions.

I normally keep my personal airplane full, but that is mainly so I don't need to deal with fuel before my next flight. It also has a useful load that allows four people and light bags with full tanks.

As far as water--anytime I've found water in a plane it has been one with topped-off tanks. Anecdotal evidence, but it makes me feel that as long as you do an appropriate pre-flight (and you don't have a plane with a fuel system notorious for sucking up water) partial tanks is safe.
 
My experience with water in the fuel is that it has always occurred when the airplane was left outside and it had rained. It was always a fuel cap problem.
 
More often than not my plane is nearly empty, I bet there's no more than 20 gallons in it right now. I see no need to keep it full and reduce my payload
 
In all my rental time, I've never had a problem telling the FBO "Hey i need no more than half-fuel when I go", and they put a note on the board or in the computer, so that the previous renters wouldn't refuel.
 
I don't think there's any FAA or manufactures guidance on filling the tanks after a flight. Of course, if you have bladder tanks, we could have a 10 page debate on the subject :popcorn:

Generally, FBO and flying clubs do this as a curtesy to the next renter. It's not a safety of flight issue.

How do you get the extra fuel out? Either you de-fuel it with a hose and gas cans or some FBO's have rig to de-fuel. Most live with it or don't fly that day. Like someone else said, a call to the FBO to not refuel will most times work.




drotto said:
As a training pilot, I was wondering how people deal with this issue. The FAA, plane rental people, clubs, etc all recommend that you fill your tanks at the end of every flight. Fine it make perfect sense to me. From a safety standpoint it keeps water out of the system. From a courtesy standpoint, if you will not be the next person using the plane, it is nice to leave it ready to go. I get it. From a practical standpoint where most 4 place planes are really 3 place, and most 6's are really big 4's, what do you do with the actual fuel if filling the seats is more important than filling the tanks?

I go get my rental plane, but a want to take 4 people up ( including me), more than likely 15 to 20 gallons will need to come out of the tanks, if the people are the magic FAA 170 lbs. How do I get that fuel out? Where do I put it?
Click to expand...
 
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Never said the FAA requires it, but the ground schools and the FAA strongly recommend filling the tanks after each flight.
 
drotto said:
Never said the FAA requires it, but the ground schools and the FAA strongly recommend filling the tanks after each flight.
Click to expand...

Old wives tales are hard to dispel, even within the government. <shock!>

Here's a little exercise.

Calculate the moisture content in air for the empty volume of your fuel tank, and see how many grams of water can theoretically condense out of it.

Now figure out how many full air exchanges would be needed to create any appreciable amount of water in the tank, as well as what magnitude of temperature swings (and humidity) would have to occur.

Unless you are leaving your plane sitting for months or years at a time without ever sumping -- as stated above, any appreciable water you may find is coming from external sources leaking in (or from the fuel truck), not condensation from within.

(remember, something you see sweating moisture outside the tank is exposed to a practically unlimited volume of moisture laden air moving past it.)
 
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Sac Arrow said:
My FBO would normally top the tanks off but if you let them know a couple days in advance that you would need less than full tanks, they would coordinate it accordingly.
Click to expand...

Just curious, how does it work with the partner thing. I thought most partnerships would want you to leave it full for the next guy or do you just true up at the end of the month. I ask, because I was looking at that partnership on a 235. A 235 doesn't really have load issues, though.
 
ElPaso Pilot said:
Old wives tales are hard to dispel, even within the government. <shock!>

Here's a little exercise.

Calculate the moisture content in air for the empty volume of your fuel tank, and see how many grams of water can theoretically condense out of it.

Now figure out how many full air exchanges would be needed to create any appreciable amount of water in the tank, as well as what magnitude of temperature swings (and humidity) would have to occur.

Unless you are leaving your plane sitting for months or years at a time without ever sumping -- as stated above, any appreciable water you may find is coming from external sources leaking in (or from the fuel truck), not condensation from within.

(remember, something you see sweating moisture outside the tank is exposed to a practically unlimited volume of moisture laden air moving past it.)
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Folks, no more calls please, we have a winner!

Over the past 50 years or so, the only water I've have in my tanks came from leaking fuel caps or was pumped into the airplane during refueling. One is a maintenance issue and the other one you don't really have much control over. However, at some "low volume" FBOs, I've been known to ask them to sump the truck in my presence. I've seen them get water in the bucket on several occasions. Not every line boy does what he's supposed the first thing when he gets to work. And by the way, how long do you need to wait after fueling for any water to settle out and make its way to the sump?
 
kgruber said:
Show me.
Click to expand...

FAA Airplane Flying Handbook section 2-5 sub heading Fuel and Oil.

The best preventive measure is to minimize the
opportunity for water to condense in the tanks. If
possible, the fuel tanks should be completely filled
with the proper grade of fuel after each flight, or at
least filled after the last flight of the day. The more fuel
there is in the tanks, the less opportunity for
condensation to occur. Keeping fuel tanks filled is also
the best way to slow the aging of rubber fuel tanks and
tank sealant
 
drotto said:
FAA Airplane Flying Handbook section 2-5 sub heading Fuel and Oil.

The best preventive measure is to minimize the
opportunity for water to condense in the tanks. If
possible, the fuel tanks should be completely filled
with the proper grade of fuel after each flight, or at
least filled after the last flight of the day. The more fuel
there is in the tanks, the less opportunity for
condensation to occur. Keeping fuel tanks filled is also
the best way to slow the aging of rubber fuel tanks and
tank sealant
Click to expand...
It's CERTAINLY not going to hurt anything, but it does set a lot of guys up for W&B and performance issues when their default fuel load is "topped off".

ElPaso Pilot said it best...
Old wives tales are hard to dispel, even within the government. <shock!>

Here's a little exercise.

Calculate the moisture content in air for the empty volume of your fuel tank, and see how many grams of water can theoretically condense out of it.

Now figure out how many full air exchanges would be needed to create any appreciable amount of water in the tank, as well as what magnitude of temperature swings (and humidity) would have to occur.

Unless you are leaving your plane sitting for months or years at a time without ever sumping -- as stated above, any appreciable water you may find is coming from external sources leaking in (or from the fuel truck), not condensation from within.

(remember, something you see sweating moisture outside the tank is exposed to a practically unlimited volume of moisture laden air moving past it.)
Click to expand...
 
John221us said:
Just curious, how does it work with the partner thing. I thought most partnerships would want you to leave it full for the next guy or do you just true up at the end of the month. I ask, because I was looking at that partnership on a 235. A 235 doesn't really have load issues, though.
Click to expand...

Best bet in a Cherokee is standardize on filling to the tabs. The partner going on a long xc can top off as needed. We keep our 140 at the tabs 98% of the time?I've never seen water come out of the sumps, but she's hangared all the time.
 
LDJones said:
Best bet in a Cherokee is standardize on filling to the tabs. The partner going on a long xc can top off as needed. We keep our 140 at the tabs 98% of the time?I've never seen water come out of the sumps, but she's hangared all the time.
Click to expand...

I have a 140, which I own with no partners. I usually just put gas in before flying (just a preference). I am trying to sell it now and I have an opportunity to buy into a partnership on a Cherokee 235. I am just not sure how I will do in a partnership (kind of like being a bachelor too long and getting set in your ways). Financially it makes sense, but I will need to learn to share.
 
flyingmoose said:
Most rentals will fly enough that the water issue will not be and issue, and personally I don't think its an issue anyway. I think if they fill it up before your rental without you telling them to then they have done you a disservice. I know they are trying to help, but you are right that sometime you just cant take out the fuel.

I don't fill my a/c up until I know what I need to use it for next. Just my 2 cents
Click to expand...
I'm with Matt. And I've never seen water get into aircraft fuel tanks unless the fuel cap was leaking or it was already in the fuel when pumped in. I know the theory about condensation forming, but I've never seen it happen in 44 years of flying.

Whoops -- it's 2014 -- make that 45 years of flying.
 
LDJones said:
Best bet in a Cherokee is standardize on filling to the tabs. The partner going on a long xc can top off as needed. We keep our 140 at the tabs 98% of the time?I've never seen water come out of the sumps, but she's hangared all the time.
Click to expand...

Our club has no actual flying rules beyond 'follow the FARs and insurance regs', but we do encourage members to leave our two Cherokees filled to the tabs. Especially in the Texas summer.

Of course, the schedule is available to all members, so if you want some particular fuel state then you just call the guy who flew it before you.
 
I live in Los Angeles and my airplane is our bug out tool for the 'big one.'

Walk to the airport, hope I can open the hangar door - and off we go to the brother in law in Phoenix - so there is always 3 hours gas in the tanks - which gives me the payload to take all 4 or us and the dog . . . .
 
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