multiple hops fuel planning

[simon-flight 0]

Hi,

 

I've started regularly flying the Alaska airlines anchorage, juneau, sitka, ketchican, seattle route and was wondering about fuel planning in general for multiple destinations.

 

If you fly to a single destination you include the ground time, holding, go arounds, extra and alternate but would you do the same for 'each' of the destinations on a multiple route ?

 

I'm guessing that all the alternates would'nt be catered for but the rest would.

 

Any experience on this ?

 

Simon

[Fabo 213]

Interesting question. I assume you wish to not add fuel anywhere enroute. What I would do:

-Start from back. Figure out fuel needed, incl. reserve, for the last leg using expected load.

-Figure out reserves required for second to last leg. It should be in most any case less than what you will have loaded for last leg. (If it is, you need to load more for 2nd to last leg)

-Take expected load for 2nd to last leg, add fuel load for last leg (maybe minus reserves for 2nd to last? Difference should be quite small though I think), and figure fuel needed to fly enroute. Add that to what you need to have loaded for last leg. Fuel figure now should look like (2nd to last enroute + last enroute + last reserves).

 

-Take expected load for 3rd to last leg, add fuel load for 2nd to last leg, figure enroute fuel, add to figure from previous flight. Fuel will now look like (3rd enroute + 2nd enroute + last enroute + last reserve). You may also want to figure out reserves to show that you comply to regulations.

 

-Do the same for all the legs.

 

 

Now, you may run into a problem here - airliner design does not expect you to land with more than a bit of fuel.That might quite possibly mean problems with MLW.

 

Also, and now I need confirmation from professional folks that I did not neglect or do something wrong, but an airliner is designed to land with empty center fuel tank. Now, this means that any fuel that you might have to have in center fuel tank might do you some bad. Reason is, fuselage is expected to weigh a maximum of specific amount, and if it weighs more on landing it will do bad things to wings and/or fuselage structure.

This is then considered in MZFW for a specific frame. - because if center tank is empty, fuselage on landing wieghs the same amount as fuselage if there was no fuel at all.

What this means for you - you can expect to have unused fuel in center tank on landing - but you must include it in your ZFW calculations and you can not exceed MZFW with it included.

 

Example, for simplicity sake I will assume wing tank capacity of 8.000kg and MZFW of 68 tonnes

 

Lets say you are flying a three-leg flight with no fueling. You know you will need 16 tonnes of fuel loaded for second leg.

This means you will have to land with 8 tonnes in center tank. Therefore you must reduce MZFW for loading purposes by 8 tonnes. New "MZFW" is 60 tonnes. If the basic empty weight was 43 tonnes, that means you can now only load 17 tonnes of payload instead of 25.

[simon-flight 0]

Thanks for the reply Fabo

 

I've only really just started fuel planning proper and up until now been flying pretty light so I've not really busted any MLW's yet. What you say makes sense so next flight I'll fly heavy and see how it all works out.

 

Thanks

Simon