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What is the mass of fuel which may be loaded, if the fuel density (specific gravity) is given as 0.79 and the maximum quantity of fuel that can be loaded into a helicopter's tanks is given as 800 US Gallons?

• A
2 873 kg
• B
4 604 kg
• C
2 392 kg
• D
3 833 kg

A relationship exist between litres and kilograms:

• 1 litre of water weighs 1 kilogram.

A similar relationship exists between pounds and imperial gallons (IG).

• 1 IG of water weighs 10 pounds.

To convert from volumes to mass or mass to volumes, you need the Specific Gravity (SG) of the fuel:

• The SG shows the relationship between litres and kilograms or between pounds and imperial gallons.

Specific Gravity 0.79 means that a volume of fuel weighs 79% of the equivalent volume of water.

For this question 800 USG shall be converted to litres by assuming 1 USG = 3.785 litres according to CAP 758 conversion table for liquids.

• Fuel in litres = 800 USG x 3.785 =3 028 litres

Knowing the value in litres we can convert the fuel into a mass by applying specific gravity:

• Fuel in kg = 3 028 litres x 0.79 = 2 392 kg

NOTE:

It is important to convert the masses and volumes into the same units of measurement, in order to get the correct answer.

1. Fuel volume is measured in: Imperial Gallons (IG), US Gallons (USG) or litres (l or lt).
2. Fuel mass is measured in: Tonnes (t or ton), Kilograms (kg) or pounds (lb).

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