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PAR · 10% of the exam

Operation of Systems practice questions

10 free Operation of Systems questions for the Private Pilot Airplane (PAR) Knowledge Test exam, each with the correct answer and an explanation for every option.

Start the questionsFree 10-question PAR quiz

What this domain covers

How aircraft systems work and what to do when they don't.

Exam weight
10%
On a real exam
≈ 6 questions
In our bank
60 questions

Topics that come up most

  • Engine and propeller operation
  • Fuel and ignition systems
  • Electrical system
  • Flight instruments and pitot-static system
  • Carburettor icing

How to study it

Know the failure symptom for each instrument or system; questions describe a symptom and ask for its cause.

Sample Operation of Systems questions

Try each one before opening the answer. Original questions written to the official exam objectives.

  1. Question 1

    On a fuel-injected engine, what protects against induction icing that blocks the air filter?

    • AAn alternate air source that opens automatically or manually
    • BCarburetor heat applied full time
    • CThe primer, used in flight
    • DPitot heat, which also warms the intake
    Show answer and explanation

    Answer: A) An alternate air source that opens automatically or manually

    • ACorrect. It bypasses a blocked intake.
    • BIncorrect. Fuel-injected engines don't have carb heat.
    • CIncorrect. The primer isn't used in flight.
    • DIncorrect. Pitot heat warms only the pitot tube.

  2. Question 2

    In an airplane with a constant-speed propeller, which sequence is generally recommended when increasing power?

    • AIncrease RPM with the propeller control, then increase manifold pressure with the throttle
    • BIncrease manifold pressure with the throttle, then increase RPM with the propeller control
    • CAdvance only the throttle, since the governor raises RPM automatically as power increases
    • DLean the mixture first, then advance the throttle, then advance the propeller control
    Show answer and explanation

    Answer: A) Increase RPM with the propeller control, then increase manifold pressure with the throttle

    To increase power with a constant-speed propeller, increase RPM first and then manifold pressure. To decrease power, reduce manifold pressure first and then RPM. This avoids high manifold pressure at low RPM.

    • ACorrect. Raising RPM before manifold pressure keeps high manifold pressure from being paired with low RPM, a combination that can overstress the engine and lead to detonation.
    • BIncorrect. Throttle first is the order used when reducing power (reduce manifold pressure, then RPM). Using it to add power briefly creates high manifold pressure at low RPM, which can overstress the engine.
    • CIncorrect. The governor holds the RPM the pilot selected by changing blade pitch. Adding throttle raises manifold pressure, not the selected RPM, so the propeller control must be moved to get higher RPM.
    • DIncorrect. Leaning before adding power is not the recommended technique; the mixture is normally enriched as needed before power increases. Throttle before propeller is also the wrong order for adding power.

  3. Question 3

    What does an illuminated low-voltage warning light usually indicate in flight?

    • AThe oil pressure is too high
    • BThe battery is overcharged and must be switched off right away
    • CThe fuel tanks are nearly empty
    • DThe alternator isn't keeping up and the battery is supplying power
    Show answer and explanation

    Answer: D) The alternator isn't keeping up and the battery is supplying power

    • AIncorrect. Oil warnings are separate.
    • BIncorrect. Low voltage means undercharging.
    • CIncorrect. Fuel warnings are separate.
    • DCorrect. Load shedding may be needed.

  4. Question 4

    If an air-cooled engine begins to overheat in a climb, what can the pilot do?

    • ALean the mixture fully and increase power to climb out of the heat
    • BEnrich the mixture, increase airspeed and reduce power
    • CClimb more steeply at a lower airspeed
    • DTurn on the carburetor heat
    Show answer and explanation

    Answer: B) Enrich the mixture, increase airspeed and reduce power

    • AIncorrect. Leaning and more power add heat.
    • BCorrect. These steps help cool the engine.
    • CIncorrect. Lower airspeed reduces cooling.
    • DIncorrect. Carb heat adds intake heat.

  5. Question 5

    Before a cold-morning start in a carbureted airplane, a pilot unlocks the primer knob and pumps it a few times. What does this accomplish?

    • AIt sends fuel directly to the cylinders, bypassing the carburetor where cold fuel vaporizes poorly
    • BIt squirts extra fuel into the carburetor throat through the accelerator pump mechanism
    • CIt pressurizes the fuel line to the carburetor as a backup for the engine-driven pump
    • DIt fills the carburetor float chamber so fuel is ready at the venturi during cranking
    Show answer and explanation

    Answer: A) It sends fuel directly to the cylinders, bypassing the carburetor where cold fuel vaporizes poorly

    The fuel primer is a manual pump that delivers fuel directly to the cylinders, bypassing the carburetor, to help start a cold engine. It should be locked when not in use.

    • ACorrect. The primer is a small hand pump that sends fuel straight to the cylinders or intake ports. This helps in cold weather, when the carburetor can't vaporize enough fuel. The knob should be locked afterward so it can't vibrate open and over-enrich the mixture.
    • BIncorrect. That describes pumping the throttle, which works the carburetor's accelerator pump. It is a separate mechanism, and doing it before a start can cause an induction fire.
    • CIncorrect. That is the job of the auxiliary or boost pump. The primer does not supply fuel pressure to the carburetor.
    • DIncorrect. Fuel flow from the tanks through the float valve fills the float chamber. The primer bypasses the carburetor completely.

  6. Question 6

    During a turn, the inclinometer ball is to the inside of the turn. The airplane is:

    • ASkidding
    • BSlipping
    • CCoordinated
    • DStalled
    Show answer and explanation

    Answer: B) Slipping

    • AIncorrect. A skid puts the ball to the outside.
    • BCorrect. Ball to the inside means a slip; add rudder toward the ball.
    • CIncorrect. The ball would be centered.
    • DIncorrect. The ball does not show stall.

  7. Question 7

    Operating at altitude with the mixture too rich can cause:

    • ADetonation and high CHT
    • BFouled spark plugs
    • CHigher fuel economy
    • DCarburetor ice only
    Show answer and explanation

    Answer: B) Fouled spark plugs

    • AIncorrect. These come from a lean mixture.
    • BCorrect. An overly rich mixture causes power loss and spark plug fouling.
    • CIncorrect. Fuel use increases.
    • DIncorrect. This is unrelated to mixture.

  8. Question 8

    During the preflight inspection before the first flight of the day, the pilot drains a fuel sample from each tank sump and the fuel strainer. What is the main reason for this?

    • ATo release vapor pressure that built up in the tanks overnight
    • BTo find and remove water and sediment that settle at the system's low points
    • CTo purge trapped air from the fuel lines and prevent vapor lock on start
    • DTo check that the fuel quantity gauges match the actual fuel level
    Show answer and explanation

    Answer: B) To find and remove water and sediment that settle at the system's low points

    Water and sediment collect at the lowest points of the fuel system, so pilots drain each sump and the strainer before flight to find and remove them. The sample also lets the pilot confirm the fuel's color, which shows its grade.

    • AIncorrect. The tank vent system equalizes tank pressure. Sump drains are at the lowest points of the system so contaminants can be removed, not to vent pressure.
    • BCorrect. Water is heavier than fuel and settles, along with sediment, in the sumps and strainer. A sample from each drain lets the pilot spot and remove it before it reaches the engine.
    • CIncorrect. Vapor lock comes from fuel vaporizing in hot lines, not from air that sumping removes. Engine priming and fuel flow are handled by the primer and pumps.
    • DIncorrect. A small sump sample says nothing about how much fuel is in the tank. Quantity is checked by looking into the tanks or using a dipstick.

  9. Question 9

    A continuous discharge reading on the ammeter in flight indicates:

    • AA fuel pump failure
    • BThe battery is fully charged
    • CNormal alternator output
    • DThe battery is draining
    Show answer and explanation

    Answer: D) The battery is draining

    • AIncorrect. This is unrelated.
    • BIncorrect. This shows discharge.
    • CIncorrect. Normal shows charge or zero.
    • DCorrect. The alternator is not meeting the load, so the battery supplies it.

  10. Question 10

    Why are cowl flaps usually opened during takeoff and climb?

    • ATo drain water from the engine compartment
    • BTo reduce cooling drag so the airplane climbs at a better rate
    • CTo warm the engine during cold starts
    • DTo increase cooling airflow at high power and low airspeed
    Show answer and explanation

    Answer: D) To increase cooling airflow at high power and low airspeed

    • AIncorrect. They control cooling air.
    • BIncorrect. Open cowl flaps add drag.
    • CIncorrect. They are opened to cool, not warm.
    • DCorrect. This prevents overheating.

Operation of Systems: FAQs

How much of the PAR exam is Operation of Systems?

Operation of Systems is 10% of the PAR exam by the official exam guide's weighting, which on a 60-question form works out to roughly 6 questions. The real exam's exact split varies by form.

What does the Operation of Systems domain cover?

How aircraft systems work and what to do when they don't.

How should I study Operation of Systems for PAR?

Know the failure symptom for each instrument or system; questions describe a symptom and ask for its cause.

Where can I practise more Operation of Systems questions?

This page has 10 free Operation of Systems questions with answers. The ExamWize PAR question bank has 60 questions in this domain. Every practice exam result breaks your score down by domain, and Review Mode re-drills the questions you missed.

Other PAR topics

Also: 15 free questions across all topics, the PAR cheat sheet and the study guide.

Get Operation of Systems exam-ready

The full PAR bank has 60 Operation of Systems questions. Timed practice exams match the real exam's length and domain weights, every result shows your score per domain, and Review Mode re-drills the questions you missed.

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Not affiliated with FAA; questions are original, written from the official exam outline, and never copied from the real exam.