Tankering Fuel

dans2992

dans2992

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Dans2992
I know that on jets, "tankering" extra fuel often costs a lot.

Is there a similar penalty on, say, a piston single when you carry an extra 30 gals or so that you don't need?

Is there an easy formula for this?
 
http://myeslfriends.com/wordpress/wp-content/uploads/2010/11/easy_button.jpg

There ya go.

Now, on to reality. No, there is no easy way. Yes there is a fuel penalty on most/many/some airplanes. Each plane will be slightly different, and each plane with different tanks will be slightly different.

For example, I have an old Bo. It has two wing tanks in front of the spar. I and one front seat passenger put the plane right at the front of the CG envelop and requires a fair amount of trim down in flight to counteract the nose heavy condition. I also have an aux tank behind the rear seats. I can fill it with 20 gals of fuel, and have never noticed at different fuel burn. I think, but only a guess, that the altered CG allows for a slightly less tail trim authority, thus saving me some drag, which is countered by the added weight of the fuel on board.

YMMV, pro driver closed course, don't try this at home, may cause anal leakage.
 
dans2992 said:
I know that on jets, "tankering" extra fuel often costs a lot.

Is there a similar penalty on, say, a piston single when you carry an extra 30 gals or so that you don't need?

Is there an easy formula for this?
Click to expand...

You have performance charts.

Add 180 lb to your gross weight.

It won't make that much difference in a small aircraft unless you run up against weight/balance limitations. It may slow your climb some; that's the biggest effect (presuming you climb slower than you cruise).

In a large aircraft, the fuel is a much larger proportion of the total weight; it's almost half the airplane's weight in a 747 with full tanks and as many meat bags as can be stuffed in.
 
dans2992 said:
I know that on jets, "tankering" extra fuel often costs a lot.

Is there a similar penalty on, say, a piston single when you carry an extra 30 gals or so that you don't need?

Is there an easy formula for this?
Click to expand...

What are you asking for?
 
For your purposes, fuel stops are far less efficient than extra fuel.
 
In jets, we have detailed data for cruise performance in various conditions at every imaginable weight; many piston aircraft provide cruise performance only at max takeoff weight. In addition, other costs you look at in jets (extra brake wear landing 10,000 pounds heavier isn't trivial) is not important in light airplanes.

All in all, in pistons it tends to be easier to top off on fuel where it is cheap and don't uplift fuel when it is expensive. Of course, that assumes that you have comfortable fuel and performance reserves. Obviously having enough gas and being prepared for contingency scenarios (some of which might actually favor having less gas onboard) takes priority.
 
I agree, most piston singles the extra fuel isn't going to make a noticeable difference in speed or fuel burn. I do tend to keep my 182 at about 1/2 full, which is still 2-3 hours worth of fuel and top it when fuel is cheap and the load allows.:D

Sac Arrow said:
For your purposes, fuel stops are far less efficient than extra fuel.
Click to expand...
 
No real easy formula cause it will depend on your plane and other factors such as weather. You would really have to crunch the numbers. But in general yes, carrying less fuel saves you money. Probably minimal, but it does. I only carry the fuel I am going to need for the flight, plus whatever else I want to add that gives me a warm fuzzy in case of emergency. Agree with Sac Arrow. It wouldn't be worth it to carry less fuel and have to make another fuel stop. At that point, best to top off the tanks.
 
"MATHEMATICS OF TANKERING [by David Esler, in the March 1991 edition of Aviation International News]

To determine the ‘break-even cost difference’ (Cbe), use the formula:

Cbe = ( (RFCh + CmT) / F(1-R) ) x ($/gal)

Where:
•R is the percentage of the fuel carried which is consumed due to carrying its own weight. The percentage is expressed as a decimal. Here 10%, that is .1, is assumed.
•F is the quantity of tankered fuel in gallons.
•Ch is the price per gallon at home base.
•Cm is the maintenance cost, including engines, per minute of flight.
•T is the additional flight time incurred by the added fuel weight, in minutes."


https://jetbroker.wordpress.com/2010/04/07/

dtuuri
 
I base fuel purchases on trip need and prices first, but then also to some degree on lower weight for OEI in the 310. I've not found fuel load to have a significant speed impact.
 
When you have a small tank,the question is mute. Would like to have the option,depending on fuel price.
 
dans2992 said:
I know that on jets, "tankering" extra fuel often costs a lot.

Is there a similar penalty on, say, a piston single when you carry an extra 30 gals or so that you don't need?

Is there an easy formula for this?
Click to expand...

Yes, there is always a penalty including carrying 30 extra gallons of fuel into a crash to help kill you.
 
docmirror said:
http://myeslfriends.com/wordpress/wp-content/uploads/2010/11/easy_button.jpg

There ya go.

Now, on to reality. No, there is no easy way. Yes there is a fuel penalty on most/many/some airplanes. Each plane will be slightly different, and each plane with different tanks will be slightly different.

For example, I have an old Bo. It has two wing tanks in front of the spar. I and one front seat passenger put the plane right at the front of the CG envelop and requires a fair amount of trim down in flight to counteract the nose heavy condition. I also have an aux tank behind the rear seats. I can fill it with 20 gals of fuel, and have never noticed at different fuel burn. I think, but only a guess, that the altered CG allows for a slightly less tail trim authority, thus saving me some drag, which is countered by the added weight of the fuel on board.

YMMV, pro driver closed course, don't try this at home, may cause anal leakage.
Click to expand...

You could alway leave one wing dry and use the other wing and the 20.
 
Ted DuPuis said:
I base fuel purchases on trip need and prices first, but then also to some degree on lower weight for OEI in the 310. I've not found fuel load to have a significant speed impact.
Click to expand...

310 fuel burn has negligible impact on CG as well so you don't have to pay any extra tail down force penalty at least.
 
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