max fuel uplift formula

[Captain_BH]

hi guys

based on the current flight plan
ZFW
TAKE W
LANDING W
RAMP FUEL
BURN OFF FUEL

How can I find ( what is the propper way - formula -to find ) max fuel could be uplifted - carried in the tanks putting in mind max landing weight.

Thanks

[dhardesthard]

I suspect that you meant the max fuel in tanks prior to engine start. If that is the case then add the weight of burn off to the max landing weight. Bear in mind that if you arrive over the Max landing weight you are going to have to get rid of the extra by dumping or increasing your burn (flaps, gear down early, early descent or holding). If you need to know how much you can uplift then subtract the fuel prior to commencement of fuelling from the above (Max fuel for dispatch). Eg. If you can take-off with 70000kgs and you already have 15000kgs before fuelling commences then your max uplift is 70000 - 15000 = 55000kgs.

[westhawk]

Try adding flight planned fuel burn to the max allowable landing weight at destination to find maximum allowable takeoff weight. Now subtract ZFW to find maximum fuel on board allowable for takeoff. Subtract the fuel already in the tanks when you found the airplane and you have your maximum uplift. Just off the top of my weary head, it could look something like this:

MFUL=(FPFB+MALW)-ZFW-FAOB

Where:
MFUL=max fuel uplift from hydrant
FPFB=flight planned fuel burn
MALW=max allowable landing weight
ZFW=zero fuel weight per the load manifest
FAOB=fuel already on board before beginning

Example calculation with fictional airplane, fictional flight segment and nice round numbers:

FPFB=100,000 lbs
MALW=300,000 lbs
ZFW= 250,000 lbs
FAOB=25,000 lbs


(100,000+300,000) - (250,000-25,000) = 125,000 MFUL

As can be deduced from the above, that airplane will have 150,000 lbs of fuel on board before starting and will land with 50,000 lbs per the flight planned fuel burn. Subtract required reserves from the maximum uplift to find the minimum uplift.

None of the above was taken from a book. It's just a method of putting to computer screen what charter pilots usually do in their head. Let the other guy you're flying with use a calculator to come up with the same number. (hopefully or you get to do it over)

[Microburst2002]

MLW minus current flight plan landing weight.

Well. Actually you can add the fuel that will be burnt due to excess fuel. Typical computer flight plans give aproximate increased fuel burnt per each extra ton of weight. You will burn it anyway and you will arrive with max ldg weight.

[Tu.114]

I am afraid the max. landing weight (or mass, if You prefer) is only one of the limiting factors.

With ZFW and fuel burn known, Your takeoff fuel can be limited by either one of the following (not looking at the distinct possibility of a high ZFW not allowing to fuel as required and therefore necessitating offloading of payload):
-structural max. TOW
-performance limited max. TOW
-structural MLW -performance limited MLW.
-fuel tank capacity.

So the maximum fuel You can have on board at the beginning of takeoff is the lowest number of the following calculations:

a. MATOW - ZFW
b. MALAW - ZFW + burnoff.
c. maximum fuel tank capacity - taxi fuel.

As You will typically stand on the ramp when the decision for uplift is to be made, the taxi fuel needs to be minded as well, and therefore the maximum ramp weight comes into play.

So the fuel on board will need to be equal to or less than the lowest of following:

a (from above) + taxi fuel
b + taxi fuel
c.

And from there on it is easy - the maximum uplift is max. FOB minus the fuel that You already have in the tanks.

For everything else, see the flight planning instructions in Your company OM-A and OM-B...

[Microburst2002]

It is easier, and takes less time at the flight dispatch desk if you just make MLW-ELW, then add the extra fuel burnt and, (it goes without saying) check that you don't exceed any limit (tank capacity, take off, ramp...).

And of course, it is advisable to leave a buffer, just in case you save fuel on the way and find yourself above MLW.

[nitpicker330]

Give the guy a calculator and some common sense.

It's not rocket science:{