double sector fuel calculations

[riqsid]

Hi guys

Could someone pls shed light into what actually double sector fuelling means ? and how payload calculations carried out for double sector fuelling ?

Will be really grateful if anyone could take your time

[Exaviator]

Tankering fuel for a second sector is quite common on large aircraft like the B-747. It is done when there is a significant disparity between fuel costs at the point of initial departure and first destination. Some of the tankered fuel will be burnt off due to the increased weight, but if there is sufficient difference in cost it can still be cost effective to uplift all, or some of the second sector fuel. You need a set of fuel differential tables to do the calculations.

Another reason for tankering, is a shortage of fuel at the intermediate stop, or interruption to supply due industrial action or other reasons.

[Tinstaafl]

If I'm reading your question correctly, you're referring to what was known as a 'milk run' problem in Oz CPL exams. You need to consider TOW & LW vs Fuel Burn vs payload added/subtracted (and loaed within CG limits too, of course)

One way is to have columns for each airstrip, below each of those MTOW available, room for weight adjustments (incl. taxi fuel) and then MLW available.

Originating Airstrip.................................................... ....Intermediate............................................ .........Final Airstrip

MTOW........................................................ .............MTOW........................................... ................................n/a
actual TOW......................................................... ......Actual TOW......................................................... ..n/a
....................\
......................\
..............................FBO from take-off 1......................Payload &...................FBO from take-off 2
..............................to landing 1...................................taxi fuel adjust..................to landing 2
............................................................ ......\
............................................................ .........\
............................................................ .................actual LW.......................................................... ....actual LW
n/a........................................................... ..............MLW ............................................................ .......MLW



You start at Airstrip 1 TOW (compare with MTOW), burn fuel diagonally down to Actual LW at an intermediate airstrip (compare with MLW) then move upwards adding/removing payload weight, fuel upload & subtract taxi fuel to arrive at Intermediate TOW. Repeat diagonally down to Actual LW at the next point and so on.

There will be a TOW or LW that is more limiting. On first pass whichever weight is most exceeded will be the most limiting. Using that MTOW or MLW work backwards & forwards with the fuel burns & payload adjustments to find the rest of the TOWs & LWs. Make sure you compare each of them with their respective limit.


Later:
Should have mentioned that there can be more than one intermediate stop. The principle is the same - include a column for each stopover and calculate fuel & payload backwards & forwards from the most limiting case.

Also MZFW and any other weight or loading limitations must be considered too.

[parabellum]

For the calulation you load the full flight plan required fuel for the second leg and the flight planned burn off + outbound/first sector contingency, that will give you total fuel required for a two sector trip carrying trip fuel from initial departure.

Don't let anyone talk you out of loading the outbound/first sector contingency fuel. If, for example, you only achieve FL270 instead of flight planned FL370 on the first leg, you will burn contingency and if you didn't include it you would then find at your first stop that you don't have flightplan fuel for the second sector.

[411A]

I would add, don't forget taxi fuel, and...anticipated taxi delays that might be encountered.
In our operation, we tanker fuel quite a lot...sometimes it saves heaps of dollars, and makes the charter customer most pleased.

[riqsid]

Thanx alot for your replies. I fully understand the reasons for double sectors fuelling. But I thought i should put forward an example to make things clearer for me.

MTOW - 73500 kgs
MLW - 64500kgs
MZFW - 60500 kgs
Max Fuel Capacity - 15000 kgs
DOM - 35000 kgs

Q1 - For a flight which requires 12000kgs of fuel, of which the burn-off is
5000kgs, what is the maximum payload that can be carried?
Answer - 22500 kgs

Q2 - If the payload is 15000kgs, what is the maximum fuel that can be
carried if the burn-off is 3000kgs?
Answer - 17500 kgs ( Pls indicate if ans correct or wrong)

Q3 - What is the maximum theoretical payload ?
Answer - 25500 kgs ( Pls indicate if ans correct or wrong)

Q4 - Double sector fuel is 14000kgs, Burn-off for the first sector is
8000kgs. Can a payload of 25000kgs be carried ? if not how much ?
(Pls answer for me with explanation. Thanks)

Q5 - For a flight with a burn off of 8000kgs and total fuel requirements of
15000kgs, can the maximum theretical payload be carried? If not how
much is the restricted ZFW?
Answer - No, restricted ZFW - 57500 ( Pls indicate if ans correct or wrong)

Thanks alot guys... Cheers

[Mad (Flt) Scientist]

Originally Posted by riqsid

Thanx alot for your replies. I fully understand the reasons for double sectors fuelling. But I thought i should put forward an example to make things clearer for me.

MTOW - 73500 kgs
MLW - 64500kgs
MZFW - 60500 kgs
Max Fuel Capacity - 15000 kgs
DOM - 35000 kgs

Q1 - For a flight which requires 12000kgs of fuel, of which the burn-off is
5000kgs, what is the maximum payload that can be carried?
Answer - 22500 kgs

At TO: max payload = 73500 - 12000 - 35000 = 26500
At LDG : max payload = 64500 - (12000-5000) - 35000 = 22500
Respecting ZFW : max payload = 60500-35000 = 25500
Lowest value applies : max payload 22500

Q2 - If the payload is 15000kgs, what is the maximum fuel that can be
carried if the burn-off is 3000kgs?
Answer - 17500 kgs ( Pls indicate if ans correct or wrong)

At TO: max fuel = 73500 - 15000 - 35000 = 23500
At LDG : max fuel = 64500 - 15000 - 35000 = 14500 hence max +3000 = 17500 at TO
Respecting fuel volume : max fuel = 15000
Lowest value applies : max fuel loaded at TO = 15000

Q3 - What is the maximum theoretical payload ?
Answer - 25500 kgs ( Pls indicate if ans correct or wrong)

Respecting ZFW : max payload = 60500-35000 = 25500
assuming no fuel constraints

Q4 - Double sector fuel is 14000kgs, Burn-off for the first sector is
8000kgs. Can a payload of 25000kgs be carried ? if not how much ?
(Pls answer for me with explanation. Thanks)

First sector, TO fuel 14000, LDG fuel 14000-8000=6000
Assuming 25000 payload:
TOM = 25000 + 14000 + 35000 = 74000 which is above MTOW so cannot go.
max payload to respect first sector MTOW is 73500-14000-35000 = 24500
max payload to respect first sector MLW is 64500-6000-35000 = 23500
So, based on first sector, max payload is 23500

Second sector has less fuel, so will be less restricted for payload, therefore double sector max payload is as determined by sector #1, i.e. 23500

Q5 - For a flight with a burn off of 8000kgs and total fuel requirements of 15000kgs, can the maximum theretical payload be carried? If not how much is the restricted ZFW?
Answer - No, restricted ZFW - 57500 ( Pls indicate if ans correct or wrong)]

TOfuel 15000, MTOW 73500 so max ZFW at TO = 73500-15000 = 58500
LDG fuel = (1500-8000)=7000, MLW = 64500 so max ZFW at LDG = 64500-7000 = 57500
MZFW 60500
Most restrictive applies i.e. 57500 as constrained on landing.

[riqsid]

Thanxxxxxxxx is all wat i can say. Thanks so much fr u tym