The amount of energy in a fuel depends on the mass of the fuel not its volume. Cars, and other vehicles, fill up at the garage using litres of fuel not kilograms. In summer, a full tank contains less energy than in winter. The Devon Air Ambulances, in common with other aircraft, fill up according to the mass of fuel. The fuel pump is calibrated in litres so the pilot has to convert fuel mass into volume before filling the helicopter. He also needs to know the temperature of the fuel. The graphs show how the volume and mass of fuel are related and how the volume of 1000 litres of fuel at 0째C changes with temperature. 1000 900 800 700 volume of fuel at 0oC in litres
600 500 400 300 200 100 0 0
100
200
300
400
500
mass of fuel in kg
600
700
800
1100 1090 1080 1070 1060 volume 1050 in litres 1040 1030 1020 1010 1000 0
10
20
30
40
50
60
70
80
90
100
temperature in째C
Since the rotors of the helicopter spin at a constant rate, the fuel consumption is independent of speed. The helicopter has a fuel consumption of 4kg/minute. The helicopter is fuelled with enough fuel to fly anywhere in Devon, collect a patient and then fly to Bristol. This journey would take 1hour 45 minutes.
Use the information to answer the following questions. 1. What is the volume of 500kg of fuel at 0째C? _____________________litres 2. What is the density of aviation fuel at 0째C? ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ 3. What mass of fuel is in the helicopter when it leaves its base? ________________________________________________________________ ________________________________________________________________ 4. The helicopter arrives back to its base with 95kg of fuel in its tank. What volume of fuel needs to be added if the temperature at the base is 25째C? ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ 5. The cruising speed of the helicopter is 260km/h. Calculate the fuel consumption in litres/kilometre at 25째C. ________________________________________________________________ ________________________________________________________________ ________________________________________________________________