4 / 20

Refer to figure.
An aircraft with a mass of 46 500 kg is flying in long range cruise at FL280, under ISA conditions. The tailwind experienced during the flight decreases from 25 kt to 10 kt, what will be the impact in ground distance covered per 1000 kg of fuel burnt?

  • A
    Decrease by 2 NM.
  • B
    Increase by 2 NM.
  • C
    Decrease by 7 NM.
  • D
    Increase by 7 NM.

Refer to figure.
For this exercise, we will need the following formula:
NGM = NAM x (GS/TAS)

Let's start by calculating the range in NAM per 1000 kg:
1. Enter the table at 46 500 kg and read the corresponding distance: 2257 NM.
After consuming 1000 kg of fuel, we will have a mass of 45 500 kg. Enter the table at 45 500 kg and read the corresponding distance: 2072 NM

  • Which gives us a range of 2257 NM - 2072 NM = 185 NM for 1000 kg

2. Calculate the TAS:
TAS will be the average between TAS at 46 500 kg and 45 500 kg.

  • From the table:
    TAS at 45 500 kg = approx. 414.5 kt
    TAS at 46 500 kg = approx. 417.5 kt
    TAS = 416 kt

3. Calculate the range when 25 kt tailwind:
NGM = 185 x (416 + 25) / 416 = 196 NGM

3. Calculate the range when 10 kt tailwind:
NGM = 185 x (416 + 10) / 416 = 189 NGM

=> As you can see from the above, when we experience a reduction of tailwind from 25 kt to 10 kt, the range decreases 196 NGM - 189 NGM = 7 NGM.

Your Notes (not visible to others)



This question has appeared on the real examination, you can find the related countries below.

  • France
    3
  • Germany
    2
Keyboard Shortcut Use Keyboard Shortcuts