Operation of Systems and High-Altitude Operations practice questions

Answer: D) Extra fuel helps cool the engine

• AIncorrect. It's a POH procedure.
• BIncorrect. Full rich uses more fuel.
• CIncorrect. The mixture doesn't control oil pressure.
• DCorrect. Follow the POH for high elevations.

Answer: A) Air pressure inside the pressurized hull and ambient air pressure outside the airplane

Cabin pressure differential is the difference between pressure inside the pressurized hull and outside ambient pressure. Relief valves automatically limit it to a predetermined maximum to protect the structure, and an instrument displays it to the crew.

• ACorrect. Pressure differential is inside pressure minus outside ambient pressure. The structure is designed for a maximum differential, and pressure relief valves automatically limit the positive differential to a predetermined value.
• BIncorrect. That comparison relates to engine induction or turbocharger performance. It has nothing to do with the load on the pressurized structure.
• CIncorrect. The outflow valve controls cabin pressure by regulating how much air is released from the cabin. The differential that relief valves limit and the gauge displays is cabin pressure versus outside atmospheric pressure, not inflow versus outflow.
• DIncorrect. That difference is the controller's error between selected and actual cabin pressure. It is not the structural pressure differential across the hull.

Answer: D) Enrich the mixture, increase RPM, then increase manifold pressure

With a constant-speed propeller, increase power by enriching the mixture, raising RPM, then raising manifold pressure. Reduce power in the reverse order (manifold pressure first, then RPM), so the engine never runs at high manifold pressure with low RPM.

• AIncorrect. Cowl flaps don't belong in the power-change sequence. Higher power makes more heat, so cowl flaps are usually opened, not closed, when power goes up for a climb.
• BIncorrect. Raising manifold pressure while RPM is still low creates high cylinder pressures that can overstress the engine. This order is used when reducing power, not increasing it.
• CIncorrect. Before increasing power, the mixture is enriched, not leaned. More fuel keeps the engine cool and helps prevent detonation at higher power.
• DCorrect. To increase power, enrich the mixture as needed, raise RPM with the propeller control, then raise manifold pressure with the throttle. This is the reverse of the reduction sequence (throttle back first, then RPM) and avoids high manifold pressure at low RPM.

Answer: B) Reset it once after a cooling period, if needed

• AIncorrect. That defeats its protection.
• BCorrect. Repeated resets can start a fire.
• CIncorrect. That can cause a fire.
• DIncorrect. That isn't possible or safe.

Answer: B) Enrich the mixture, open the cowl flaps and increase airspeed

To lower high cylinder head temperatures, enrich the mixture, open the cowl flaps and increase airspeed with a shallower climb; reducing power also helps. Leaning, closing the cowl flaps or slowing down all reduce cooling.

• AIncorrect. All three actions make overheating worse: a leaner mixture runs hotter, closed cowl flaps cut airflow over the cylinders, and lower airspeed reduces cooling.
• BCorrect. Extra fuel helps cool the cylinders, open cowl flaps let more air through the engine compartment, and higher airspeed (a shallower climb) increases cooling airflow.
• CIncorrect. Opening the cowl flaps helps, but leaning raises temperatures, and a steeper climb at lower airspeed cuts cooling airflow while the engine works at high power.
• DIncorrect. Enriching helps, but closing the cowl flaps and slowing down both reduce the airflow the engine needs for cooling.

Answer: A) Outflow valve, which meters how much air leaves the cabin

The pressurization source supplies a fairly steady flow of air into the cabin. The cabin pressure controller sets cabin altitude by modulating the outflow valve. The safety and dump valves are protective or emergency devices, not the normal control.

• ACorrect. Air comes into the cabin from the pressurization source at a fairly steady rate. The controller modulates the outflow valve to release more or less of that air, and this sets the cabin pressure and therefore the cabin altitude.
• BIncorrect. The safety (positive-pressure relief) valve is a backup. It opens only to stop the cabin from going over the maximum pressure differential. It does not control cabin altitude in normal operation.
• CIncorrect. The dump valve releases cabin pressure to the atmosphere when the pilot selects it, for example in an emergency or on the ground. It does not continuously regulate cabin altitude.
• DIncorrect. The pressurization source (turbocharger compressor, engine bleed air or pneumatic pump) supplies air at a fairly constant rate. Cabin altitude is controlled by regulating the air going out, not the air coming in.

Answer: C) Gyro instruments

• AIncorrect. That's static.
• BIncorrect. That's pitot-static.
• CCorrect. The attitude and heading indicators in many light airplanes.
• DIncorrect. That's self-contained.

Answer: B) Decreases

• AIncorrect. It decreases.
• BCorrect. Air pressure drops with altitude.
• CIncorrect. Only turbocharging can hold it.
• DIncorrect. It decreases.

Answer: D) Manifold pressure above the engine's limit

• AIncorrect. That's not overboost.
• BIncorrect. That's not overboost.
• CIncorrect. That's not overboost.
• DCorrect. It can damage the engine.

Answer: C) A loadmeter shows load, not discharge

• AIncorrect. That's a voltmeter.
• BIncorrect. They show different things.
• CCorrect. A center-zero ammeter shows charge or discharge.
• DIncorrect. That's a fuel flow gauge.