How do variable-pitch propellers work in flight simulators?

A variable-pitch propeller changes blade angle for take-off, climb, cruise or descent. Most in-flight systems use a constant-speed governor, which varies that angle automatically to hold the RPM selected with the propeller lever. Use high RPM for take-off and climb, lower RPM for cruise, and follow the simulated aircraft's checklist and operating limits.

In real-world aviation and civil flight simulators such as Microsoft Flight Simulator, X-Plane, FSX and Prepar3D, variable pitch is an umbrella term. The exact behaviour depends on the aircraft's propeller system and how completely that particular simulation models it.

What does changing propeller pitch do?

Changing pitch alters how heavily the blades load the engine and how efficiently they meet the relative airflow. The blade angle is not quite the same thing as aerodynamic angle of attack, because the latter also changes with RPM and forward speed.

• Fine pitch uses a relatively small blade angle. It places less load on the engine and permits high RPM, making it suitable for take-off, initial climb and a go-around.
• Coarse pitch uses a larger blade angle. It absorbs more torque per revolution and permits lower RPM, usually reducing noise and improving cruise operation.
• Feather turns the blades nearly edge-on to the airflow to reduce drag after an engine shutdown or failure. Only suitably equipped propellers can feather.
• Reverse pitch produces reverse thrust for ground deceleration on aircraft designed for it. It is not an ordinary descent or landing setting.

On a constant-speed installation, pushing the propeller lever fully forward selects maximum governed RPM; it does not lock the blades permanently in fine pitch. The governor continues moving them as required. Our explanation of how engine power, RPM and propeller blade angle interact covers the underlying engine relationship.

Is variable pitch the same as constant speed?

No. Constant speed is one type of variable-pitch system, and it is the type most sim pilots encounter in complex piston aircraft and turboprops.

In a constant-speed system, RPM above the selected value makes the governor command a coarser angle; RPM below the target makes it command a finer angle, within the propeller's mechanical limits. The oil-pressure and counterweight arrangement differs between designs, but that governing result is what matters in the cockpit.

What do the throttle and propeller lever control?

In a typical constant-speed piston aircraft, the throttle controls engine power while the propeller lever selects RPM. The mixture lever then adjusts the fuel-air mixture.

Do not treat the propeller lever as a second throttle. If the three controls are being confused, our guide to using throttle, propeller and mixture levers together explains the standard quadrant layout.

Turboprops may use a power lever for torque, a propeller lever for RPM and a condition lever for fuel or idle selection. Some newer aircraft combine these functions electronically, so their checklist may not resemble the three-lever piston procedure.

How do I configure a propeller control in a flight simulator?

Bind a spare hardware axis to the propeller control, then confirm that its direction and range match the cockpit lever.

1. Check the aircraft first. A fixed-pitch Cessna or similar trainer has no usable propeller lever. Choose an aircraft fitted with a constant-speed or controllable-pitch propeller.
2. Assign the correct command. Control names vary, but look for entries such as Propeller Axis, Propeller RPM or propeller-pitch increase and decrease commands. Multi-engine aircraft may provide separate controls for each engine.
3. Test the direction. Moving the hardware lever forward should move the cockpit propeller lever forward and select higher RPM. Reverse or invert the axis if it moves the wrong way.
4. Remove conflicting assignments. A second throttle, joystick slider or gamepad axis bound to the same command can make the cockpit lever jump or return by itself.
5. Disable automatic management while testing. Propeller or engine assistance can override manual input. Some detailed add-ons also require their own supported command rather than a generic pitch axis.

For a practical hardware example, see our worked setup for assigning general-aviation engine controls to a HOTAS.

How do I use a constant-speed propeller during a flight?

For a typical piston aircraft, use maximum selected RPM for take-off, then set the published climb and cruise RPM rather than choosing figures by guesswork.

1. Use the aircraft checklist. Find the approved RPM, manifold-pressure and temperature limits. Procedures differ between naturally aspirated, turbocharged and geared engines.
2. Start and perform the run-up. The propeller lever is normally forward unless the checklist says otherwise. Cycle the propeller only when instructed; this checks governor operation and circulates warm oil through the hub.
3. Take off at the specified RPM. Select the take-off propeller setting, advance the throttle smoothly and check that RPM stabilises without exceeding the red line.
4. Set climb power. After take-off, establish the published climb manifold pressure and RPM. When reducing both controls, throttle normally comes back before RPM.
5. Set cruise power. Reduce throttle to the approved manifold pressure, select the recommended cruise RPM and lean the mixture as required. Lower RPM may reduce noise and improve efficiency, but only approved power combinations should be used.
6. Manage the descent. Do not push the propeller control forward abruptly at high airspeed merely because the aircraft is descending. Retain the cruise setting until the checklist calls for approach RPM, then move the lever smoothly.
7. Prepare for a go-around. Select the required propeller RPM and mixture setting, then apply power smoothly in the aircraft's specified order.

When increasing piston-engine power, the useful default is RPM first and throttle second; when reducing power, throttle comes back before RPM. The aircraft flight manual takes precedence. The old rule that manifold pressure must always be numerically lower than RPM divided by 100 is not universal—many engines have approved so-called oversquare settings.

Why does the propeller lever do nothing in the simulator?

A motionless RPM gauge does not always indicate a broken control. Check the operating state before changing assignments.

• The aircraft has a fixed-pitch or ground-adjustable propeller. Select a properly modelled constant-speed aircraft.
• The engine is below governing range. At idle or low power, the blades may be against the fine-pitch stop, so pulling the lever back produces little or no RPM change. Test it at the checklist's run-up power.
• The axis is reversed or incomplete. Watch the animated cockpit lever and inspect the full input range during calibration.
• Another device is sending inputs. Clear duplicate propeller assignments from every connected controller.
• Engine assistance is active. Disable automatic propeller or engine management before testing manual control.
• The aircraft uses simplified or custom logic. The cockpit lever may animate even when the governor is not fully simulated, or the add-on may expect a different command.

If RPM exceeds its limit in flight and the governor will not hold the selected value, reduce power rather than repeatedly moving the propeller lever. In a failure-capable simulation, this may represent a governor, oil-pressure or propeller-system fault.

When should I use feather or reverse pitch?

Feather only an equipped propeller when the aircraft's shutdown or engine-failure checklist calls for it. In a multi-engine aircraft, identify the failed engine carefully before moving its propeller control; feathering the operating engine removes useful thrust.

Use reverse pitch only where the aircraft permits it, normally after touchdown or during approved ground manoeuvring. Configure a detent, dead zone or separate reverse command so an ordinary reduction to idle cannot accidentally select beta or reverse range in flight.