An aircraft with a TAS of 300 kts has a fuel burn of 3000 kg/hr. The specific air range as a ratio of distance travelled per tonne of fuel would be most correctly expressed as a ratio of

• A. 100nm/Tonne
• B. 30nm/Tonne
• C. 1000nm/Tonne
• D. 1nm/Tonne

Answer: (A)

Specific air range is how far you can travel for each unit of fuel burned. Here, you’re flying at 300 knots, which means 300 nautical miles in one hour. The aircraft uses fuel at 3000 kg per hour, which is 3 tonnes per hour.

To get distance per tonne, divide the distance per hour by the tonnes burned per hour: 300 nautical miles ÷ 3 tonnes = 100 nautical miles per tonne.

Equivalently, distance per kilogram is 300 nm per 3000 kg = 0.1 nm/kg, and 0.1 nm/kg × 1000 kg/tonne = 100 nm/tonne.

So the correct expression is 100 nautical miles per tonne.