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You are flying an aircraft with a cruise fuel consumption of 10 USG/hr. How much fuel will be consumed flying a 30 NM leg at a ground speed of 78 kt?

  • A

    3.8 litres

  • B

    17 litres

  • C

    38 litres

  • D

    15 litres

We need to take care with our units in this question. Our fuel consumption is provided in USG/hr, but the answer options are in litres!

A good first step is to convert USG to litres. We can either use a flight computer like the CRP1 (if this is permitted by your competent authority) or we can recall the approximate unit conversion:

1 USG = 3.8 litres

So, the fuel consumption will be 10 x 3.8 = 38 litres/hr

Now we can calculate how long we will be flying, and how much fuel we will burn in litres:

Time = Distance/Speed = 30 NM / 78 NM/hr = 0.385 hr
Fuel consumption = (38 litres/hr) x (0.385 hr) = 14.6 litres
(The closest available answer is 15 litres)

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

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