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A transport helicopter with a tank capacity of 2 532 litres is to operate a flight carrying the maximum possible fuel load with a fuel density of 0.79 kg/l. Given the following information, calculate the permissible Take-Off Fuel load:

Performance limited take-off mass (MTOM): 8 300 kg
Performance limited landing mass (MLM): 7 920 kg
Dry Operating Mass (DOM): 5 400 kg
Traffic Load for flight: 1 500 kg
Taxi Fuel: 35 kg
Trip Fuel: 710 kg
Contingency and Final Reserve Fuel: 105 kg
Alternate Fuel: 380 kg
Additional Fuel: 150 kg

  • A
    1 785 kg
  • B
    1 400 kg
  • C
    2 000 kg
  • D
    1 435 kg

Refer to figures.
Dry Operating Mass (DOM) is the total mass of the helicopter ready for a specific type of operation excluding all usable fuel and traffic load.

Convert fuel tank capacity from volume to mass by:

  1. Fuel mass = Fuel volume x Specific Gravity = 2 532 litres x 0.79 = 2 000 kg

The question is asking for the Maximum permissible Take-Off Fuel (TOF). In order to calculate the TOF the block fuel is necessary to be known.

Block fuel is the total fuel onboard for the flight:

  1. Block fuel = taxi + trip + contingency & final reserve + alternate + additional fuel
  2. Block fuel = 35 kg + 710 kg + 105 kg + 380 kg +150 kg = 1 380 kg
  3. TOF = Block fuel - Taxi fuel = 1 380 - 35 kg = 1 345 kg

Calculate the underload (the difference between actual mass and limit mass) for performance limiting take-off mass by:

  1. Underload = MTOM - DOM - TOF - TL
  2. Underload = 8 300 kg - 5 400 kg - 1 345 kg - 1 500 kg = 55 kg

Calculate the underload for performance limiting landing mass by:

Landing Fuel (LF) = TOF - Trip fuel = 1 345 kg - 710 kg =635 kg

  1. Underload = MLM - DOM - LF - TL
  2. Underload = 7 920 kg - 5 400 kg - 635 kg - 1 500 kg = 385 kg

Knowing that we have 55 kg from the all up weight for the performance limiting take off mass and 385 kg from the performance limiting landing mass. The most limiting mass is for take off and therefore, maximum permissible take off fuel will be:

  1. 1 345 kg + 55 kg = 1 400 kg (within the fuel tank capacity of 2 000 kg)
NOTE:
For this type of questions, it’s advised to make a table with the different masses. Thus, giving a visual and simplified way of solving the question.

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