Important Note: Based on latest feedback, it appears that another version of this question (339430), with different values, exists with an annex. However, the method of calculation remains the same. We are currently gathering more details and will create a new question once the annex information becomes available.

AMC1 CAT.OP.MPA.181 Fuel/energy scheme — fuel/energy planning and in-flight re-planning policy — aeroplanes
BASIC FUEL SCHEME — PRE-FLIGHT CALCULATION OF USABLE FUEL FOR PERFORMANCE CLASS A AEROPLANES
For the pre-flight calculation of the usable fuel in accordance with point CAT.OP.MPA.181, the operator should:

(f) for additional fuel, include an amount of fuel that allows the aeroplane to proceed, in the event of an engine failure or loss of pressurisation, from the most critical point along the route to a fuel en route alternate (fuel ERA) aerodrome in the relevant aircraft configuration, hold there for 15 minutes at 1 500 ft (450 m) above the aerodrome elevation in standard conditions, make an approach, and land;

To calculate this, you must find the difference between the block fuel and critical fuel scenario. If the fuel required for the trip is greater than the fuel required for the critical fuel scenario, there is no need to take additional fuel, however if it is not enough, the difference between must then be added as additional fuel.

ETP stands for equal time point, also known as Critical Point (CP).

For this scenario, there are 2 critical points along the flight. At ETP1, you would have 8100 kg of fuel left to reach your destination but in case of an emergency you would need 8260 kg to reach your alternate airport, hold and land. In this case, the difference in fuel (8260 - 8100 = 160 kg) should be added as additional fuel.

The same calculation should be done for ETP2: 6360 - 6250 = 110 kg.

The higher of the two differences (160 kg from ETP1) should be used for the additional fuel, ensuring that the aircraft will have enough fuel to handle either emergency scenario and safely reach the alternate airport.