03 Carburettor

As air enters the restriction of a Venturi, velocity _______, static or ambient pressure _______, and temperature _______.

• Increases, Increases, Increases

• Increases, Decreases, Decreases

• Decreases, Increases, Decreases

• Decreases, Decreases, Increases

Detonation is:

• Harmful to the pistons.

• Also known as 'piston slap'.

• Part of normal engine running.

• Cannot be identified externally.

If you suspect carburettor icing when flying an aircraft whose engine is not fitted with a carburettor air-temperature gauge, the correct action would be:

• To select the appropriate amount of carburettor heat depending on the amount of icing suspected.

• To always select full carburettor heat.

• To always select full carburettor heat unless the engine starts to run roughly, at which point the carburettor heat should be selected to cold.

• To open the throttle to make up for the lost power.

Pre-ignition in a four stroke piston engine is:

• Caused by a rich mixture in a hot engine.

• The fuel / air mixture burning earlier than it should.

• The explosive combustion of the fuel-air mixture.

• Characterised by the ringing nature of the explosion it causes.

It is possible to get carburettor icing when the relative humidity is greater than 50% within a temperature range of:

• 0°C and below.

• -7 to +33°C.

• -20 to +10°C.

• At any temperature.

While taxiing in an aircraft fitted with a fixed pitch propeller, you suspect that you have carburettor icing. The correct action to take would be to:

• Select carburettor heat to fully hot and leave this setting selected until you have taken off and are climbing away.

• Select carburettor heat to fully hot; then select cold as the rpm drops.

• Select carburettor heat to fully hot. Then, before take-off, select carburettor heat cold, making sure that the engine develops the correct minimum take-off rpm.

• Avoid the use of carburettor heat on the ground, and rely on the heat of the engine within the cowlings to melt the ice.

The significance of using the chemically correct mixture of air and fuel is that:

• It is the one usually used.

• It is 15:1 by volume.

• It allows complete combustion to occur.

• It gives the best results.

Pre-ignition:

• Is also known as pinking.

• Occurs after ignition.

• Is usually caused by a hot spot in the combustion chamber.

• Happens after the spark occurs at the plug.

Detonation is:

• Unstable combustion.

• An explosion that occurs before the normal ignition point.

• Usually associated with a rich mixture and high cylinder head temperature.

• Usually associated with a weak mixture and a low cylinder head temperature.

On a constant speed propeller aircraft whose engine is fitted with a carburettor, the indications of induction system icing are:

• A rise in manifold pressure and a reduction in air-speed, in level flight.

• That opening the throttle lever will not increase engine RPM.

• A gradual drop in engine rpm and possible rough running and vibration.

• A drop in manifold pressure or a reduction in air-speed, in level flight.