17 / 20

Given the following information, calculate the required sector fuel in US gallons for a Twin-Engined Turbine Helicopter:

SAR: 7.55 SM/USG
Sector distance: 88 NGM
TAS: 76 kt
Wind: 15 kt headwind

  • A
    17.9 USG
  • B
    19.2 USG
  • C
    12.6 USG
  • D
    16.7 USG

Specific Air Range (SAR) is a measure of fuel efficiency and indicates the Air distance covered per unit of fuel used. One thing that SAR does not account for is the wind.

The greater the SAR, the greater the efficiency and is given by the formula:

  • SAR = TAS / FUEL FLOW = NAMs / Unit of fuel.

SAR 7.55 SM/USG means that the helicopter covers 7.55 Statute air miles, burning 1 USG.

To calculate the required trip fuel proceed as follows:

  1. Convert SAR in SM/USG into SAR in NAM/USG (knowing that: 1 NM = 1.15 SM). So, 7.55 SM = 7.55/1.15 = 6.56 NAM. Thus, SAR = 6.56 NAM/USG.
  2. The Groundspeed is: TAS - Headwind component = 76 kt - 15 kt = 61 kt.
  3. The Sector Air distance covered is: NAM = NGM x (TAS/GS) = 88 NM x (76 kt/ 61 kt) = 109.6 NAM.
  4. Therefore, since the helicopter covers 6.56 NAMs burning 1 USG, then the Required Sector Fuel is: Sector distance in NAM / SAR = 109.6 NAM / 6.56 = 16.7 USG.

Your Notes (not visible to others)



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

Keyboard Shortcut Use Keyboard Shortcuts