Extra Fuel
We are going to look at calculating what the fuel penalty is for carrying extra fuel and how much extra fuel can be loaded.
On Computer flight plans you will find a fuel burn correction per 1000kg and for larger aircraft may get one per 3000kg. This will be in relation to take-off weight. EASA will also give a correction for landing weight.
We will now use the same question with slightly different parameters to highlight the areas to focus on.
We must ensure we do not exceed any of the following:
Maximum Zero Fuel Mass (MZFM)
Maximum Take-off Mass (MTOM)
Maximum Landing Mass (MLM)
Maximum fuel Tank Capacity
You will see that I have drawn a table to help with the calculation.
Given the following planning data, calculate the maximum possible extra fuel in kg, including any fuel penalty, that can be uplifted:
Maximum take-off mass (MTOM): 77000 kg
Maximum landing mass (MLM): 66360 kg
Maximum zero fuel mass (MZFM): 62720 kg
Dry operating mass (DOM): 42845 kg
Traffic load: 17460 kg
Planned take-off fuel: 10365 kg
Trip fuel: 7890 kg
Taxi fuel: 195 kg
Maximum fuel tank capacity: 21000 kg
Fuel burn-off correction per 1000 kg of Extra Fuel based upon:
T/O Mass: +135.0 kg; LDG Mass: +156.1 kg.
ZFM | TOM | LM | FUEL |
DOM + PAYLOAD | ZFM + T/O Fuel | ATOM – Trip Fuel | Planned T/O Fuel + Taxi |
42845 + 17460 | 60305 + 10365 | 70670 7890 | 10365 + 195 |
60305 | 70670 | 62780 | 10560 |
In limits | In Limits | In Limits | In Limits |
| Underload (MTOM – ATOM) | Underload (MLM – ALM) | Underload (Max Fuel – Block Fuel) |
| 77000 – 70670 | 66360 – 62780 | 21000 – 10560 |
| 6330 | 3580 | 10440 |
From the table we can see that the LOWEST of the underloads is that for the Landing Mass which means it is the most limiting. We now need to do the penalty correction to see what we can load.
In this case we divide the landing mass underload by 1000 and then multiply by the landing mass correction:
(3580 ÷ 1000) x 156.1 = 558.8 kg
3580 + 558.8 = 4138.8 rounded up 4139 kg
What we are saying is that if we want to land with an extra 3580 kg in tanks i.e., max landing mass then we need to load 4139 kg on top of the original planned fuel load as we will burn 559 kg of the 4139 kg, we have loaded.
We have not yet finished as we must now check that the 4139 kg does not exceed either the take-off mass underload or the fuel tank capacity.
Final check 60305 + 10365 + 4139 = 74809 kg which is less than 77000 kg.