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A crew finds that the actual headwind is stronger than the forecast wind, and so flies at 140 kt TAS instead of the planned 130 kt TAS to minimise the delay to arrival. Determine the increase in fuel use for the flight leg, given:

Fuel flow at 130 kt TAS: 162 kg/h
Fuel flow at 140 kt TAS: 188 kg/h
Forecast headwind component: 10 kt
Actual headwind component: 25 kt
Leg distance: 166 NM

  • A

    11 kg

  • B
    15 kg
  • C
    25 kg
  • D
    47 kg

1) Determine the planned fuel consumed flying at 130 kt TAS:

Planned TAS: 130 kt
Forecast headwind: 10 kt
Therefore, the planned ground speed = 120 kt

Planned flight time (to cover 166 NM) = 166 NM / 120 kt = 1 h 23 min
Fuel flow at 130 kt TAS = 162 kg/h

Planned fuel consumed = 162 kg/h x 1 h 23 min = 224 kg


2) Determine the actual fuel consumed flying at 140 kt TAS:

Actual TAS: 140 kt
Actual headwind: 25 kt
Therefore, the actual ground speed = 115 kt

Actual flight time (to cover 166 NM) = 166 NM / 115 kt = 1 h 26 min
Fuel flow at 140 kt TAS = 188 kg/h

Actual fuel consumed = 188 kg/h x 1 h 26 min = 271 kg


3) Determine the fuel increase:
  • 271 kg - 224 kg = 47 kg

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