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Quiz: 7 Questions To See How Much You Know About Aircraft Engines

Boldmethod

If you can find the ignition switch, you can drive a car. But you need to know a little more about your plane...


  1. 1) You push the throttle full forward too quickly on a carbureted engine, and the engine sputters. That's because:

    You've starved the engine by leaning the mixture.  When you push the throttle forward rapidly, the carburetor's butterfly valve swiftly opens - quickly increasing airflow.  However, the increase in fuel flow lags behind, effectively leaning the mixture and starving the engine.  Normally, an accelerator pump helps push more fuel into the airflow when you quickly open the throttle, but it often can't push enough fuel to keep the mixture stable if you're too abrupt.

    You've starved the engine by leaning the mixture.  When you push the throttle forward rapidly, the carburetor's butterfly valve swiftly opens - quickly increasing airflow.  However, the increase in fuel flow lags behind, effectively leaning the mixture and starving the engine.  Normally, an accelerator pump helps push more fuel into the airflow when you quickly open the throttle, but it often can't push enough fuel to keep the mixture stable if you're too abrupt.

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  2. 2) Which of the following gauges DOES NOT give you a good idea of your engine's operating temperature?

    Exhaust Gas Temperature: This gauge measures the temperature of the air in the exhaust manifold - which helps you identify when your mixture's set to the ideal ratio of fuel and air.  However, it wont respond to cylinder cooling.  Your Cylinder Head Temperature gauge directly measures the cylinder's temperature, which gives you a nearly immediate indication of engine cooling.  The Oil Temperature gauge takes time to respond, but it gives you a delayed indication of engine temperature.

    Exhaust Gas Temperature: This gauge measures the temperature of the air in the exhaust manifold - which helps you identify when your mixture's set to the ideal ratio of fuel and air.  However, it wont respond to cylinder cooling.  Your Cylinder Head Temperature gauge directly measures the cylinder's temperature, which gives you a nearly immediate indication of engine cooling.  The Oil Temperature gauge takes time to respond, but it gives you a delayed indication of engine temperature.

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  3. 3) If you turn the ignition key off and spin the propeller by hand:

    Anytime you spin the propeller, you turn the magnetos - which generates electricity.  However, when your ignition switch is "Off," a p-lead (short for primary lead) prevents the magneto from sending electricity to the distributor and on to the spark plugs.  Instead, the electricity from the magneto's primary coil flows through a ground wire (the p-lead) to the aircraft's fuselage.  However, if the p-lead is broken, electricity will flow from the magneto to the spark plugs - whether the switch is off or on.

    Anytime you spin the propeller, you turn the magnetos - which generates electricity.  However, when your ignition switch is "Off," a p-lead (short for primary lead) prevents the magneto from sending electricity to the distributor and on to the spark plugs.  Instead, the electricity from the magneto's primary coil flows through a ground wire (the p-lead) to the aircraft's fuselage.  However, if the p-lead is broken, electricity will flow from the magneto to the spark plugs - whether the switch is off or on.

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  4. 4) If one of your magnetos fails (and the other still operates):

    Each magneto powers one spark plug in every cylinder.  If one magneto fails, one plug in each cylinder won't fire.  You'll lose a little power because your cylinders burn fuel less efficiently with only one spark plug, but your engine will still run.  Each magneto is wired as an independent system, so one magneto can't send a spark to both plugs in a cylinder.  And, the alternator and battery make up an entirely separate system - so they can't help out if a magneto fails.

    Each magneto powers one spark plug in every cylinder.  If one magneto fails, one plug in each cylinder won't fire.  You'll lose a little power because your cylinders burn fuel less efficiently with only one spark plug, but your engine will still run.  Each magneto is wired as an independent system, so one magneto can't send a spark to both plugs in a cylinder.  And, the alternator and battery make up an entirely separate system - so they can't help out if a magneto fails.

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  5. 5) When you turn on carburetor heat (and don't have carb ice):

    Carburetor heat sends unfiltered, warm air through your carburetor.  Your carb still receives the same amount of air, but since it's warmer than the outside air, it's less dense.  This effectively enrichens your mixture.  And, if you're properly leaned, your engine's RPM drops.

    Carburetor heat sends unfiltered, warm air through your carburetor.  Your carb still receives the same amount of air, but since it's warmer than the outside air, it's less dense.  This effectively enrichens your mixture.  And, if you're properly leaned, your engine's RPM drops.

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  6. 6) An accelerator pump:

    An accelerator pump adds fuel to the airflow in your carburetor when you swiftly open the throttle.  This prevents the mixture from leaning and the engine from dying.  However, fast throttle movements toward open can still cause your engine to sputter.

    An accelerator pump adds fuel to the airflow in your carburetor when you swiftly open the throttle.  This prevents the mixture from leaning and the engine from dying.  However, fast throttle movements toward open can still cause your engine to sputter.

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  7. 7) Your starter connects to your engine:

    The starter usually connects to a gear located behind your propeller at the front of your crankshaft.  However, on some engines, the starter connects to the the crankshaft on the back of the engine - through the accessory section.  The belt you see at the front of your engine powers your alternator.

    The starter usually connects to a gear located behind your propeller at the front of your crankshaft.  However, on some engines, the starter connects to the the crankshaft on the back of the engine - through the accessory section.  The belt you see at the front of your engine powers your alternator.

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You should spend some time with your mechanic, or your POH...

Your score: % Better luck next time.

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Not bad...

Your score: %

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Nailed it!

Your score: % Well done.

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Colin Cutler

Colin is a Boldmethod co-founder, pilot and graphic artist. He's been a flight instructor at the University of North Dakota, an airline pilot on the CRJ-200, and has directed development of numerous commercial and military training systems. You can reach him at colin@boldmethod.com.

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