12 / 20
Which of the following options best describes the relationship between fuel flow and TAS, for propeller-driven aeroplanes?
  • A
    With increasing TAS, fuel flow will increase, when flying below the minimum power speed.
  • B
    With increasing TAS, fuel flow will increase, when flying above the minimum power speed.
  • C
    With increasing TAS, fuel flow will decrease, when flying above the minimum power speed.
  • D
    With decreasing TAS, fuel flow will decrease, when flying below the minimum power speed.

Refer to figure.
Power required is the product of drag multiplied by the TAS flown: Pwr required = DRAG x TAS. Thus, with increasing TAS, parasite drag increases and as a consequence the power required increases too.

The minimum power required is produced when the aircraft is flying with the minimum power required speed (VMP), which exists at the lowest point of the power required curve.

For a propeller-driven aircraft, VMP is also the best endurance speed, which gives the minimum power required to maintain level flight and is the point where the product of speed and drag (DRAG x TAS) are at a minimum.

Any increase or decrease of the TAS above or below the VMP correspondingly, increases the power required and as a result the fuel flow and decreases the aircraft’s endurance.

Your Notes (not visible to others)



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