CORRECT!

6). The mixture control can be adjusted, which

a). prevents the fuel/air combination from becoming too rich at higher altitudes.
b). regulates the amount of air flow through the carburetor's venturi.
c). prevents the fuel/air combination from becoming lean as the airplane climbs.
The answer is:
a). prevents the fuel/air combination from becoming too rich at higher altitudes.

As a normally-aspirated (i.e., using a carburetor) aircraft climbs, the air becomes thinner with increasing altitude. This would result in a mixture that would become increasingly richer and ultimately unable to support continued combustion. Thus the need for a way to control the amount of fuel in the air/fuel ratio. As the aircraft climbs, the mixture should be leaned according to the POH to mantain the optimum air/fuel ratio.

Of course, the mixture needs to be richened again during descent or the mixture will become too lean to support continued combustion. Again, follow the POH and use a checklist!

back