Calculate the Specific Air Range for TAS 450 kts and fuel burn 4500 kg/hr.

• A. 100 nm/tonne
• B. 90 nm/tonne
• C. 110 nm/tonne
• D. 120 nm/tonne

Answer: (A)

Specific Air Range shows how far you can travel for each unit of fuel consumed. It comes from the idea that distance equals speed times time, and time equals fuel onboard divided by fuel burn rate.

Endurance = FuelOnBoard / FuelBurnRate. Range = TAS × Endurance. To express this per tonne of fuel, divide Range by the fuel on board in tonnes. This leads to a handy formula: SAR = 1000 × TAS / FuelBurnRate, with TAS in knots and fuel burn in kg/hour.

Plugging in the numbers: TAS = 450 knots, fuel burn = 4500 kg/hour.

SAR = 1000 × 450 / 4500 = 100 nm per tonne.

You can also see it by thinking in one hour: you cover 450 NM while burning 4500 kg, which is 4.5 tonnes. Distance per tonne = 450 NM / 4.5 tonnes = 100 NM/tonne.

This calculation assumes no wind or wind effects are neglected; wind would change ground distance, but not the air-range concept itself. The result is 100 nm per tonne.