Flying Helicopters

Learning to fly a helicopter is challenging. If flying an airplane can be compared to riding a bicycle, then flying a helicopter is more like riding a unicycle ... while juggling.

Helicopters are so difficult to fly because they are inherently unstable. Whereas an airplane can be "trimmed" and left alone, a helicopter left to its own devices will begin to oscillate, and will eventually crash. Preventing these oscillations from developing is part of the pilot's job, but it's a task that can be a nerve-wracking experience for a beginner.

It takes an average student 10 to 15 hours to master the basics of flying a real helicopter. The average Flight Simulator pilot needs about six hours to get the basics down in the simulated Robinson R22 Beta II or Bell 206B JetRanger III. Your first few hours can be frustrating, but hang in there. The very characteristics that make helicopters challenging to fly also make them a lot of fun. And once you master the subtleties of rotary flight, there's nothing like it.

You'll have a lot more fun with the helicopters in Flight Simulator if you learn a little about rotorcraft flight before you try to take off.

To begin your helicopter adventures

Fly Tutorials 9-12 in the Missions list.

Read the rest of this article.

Read the Robinson R22 Beta II and Bell 206B JetRanger III aircraft information articles.

Practice, practice, practice.

Rotors are Wings

To understand helicopter aerodynamics, remember that a helicopter's main rotor system acts as its wings. Because rotors are airfoils, they produce lift much like an airplane's wings, and they react to changes in angle of attack—and stall—just like wings.

In an airplane, lift is generated by the wings, and thrust is generated by the propeller. In a helicopter, lift and thrust are generated by the same component: the main rotor blades. The circular area defined by the rotation of the blades is called the "rotor disk." In simple terms, the rotor disk pushes the air down, and the helicopter goes up. If the rotor disk is tilted, the helicopter moves in the direction of the tilt. When the main rotor turns, an equal and opposite force turns the helicopter's fuselage in the other direction. The tail rotor compensates for this torque.

Special Aerodynamic Effects

The operating characteristics of helicopters create special aerodynamic conditions that a pilot must understand. Among the most important are:

Ground Effect

Ground effect refers to an decrease in induced drag as an aircraft flies near the surface. In a helicopter, ground effect is defined as an increase in performance when the helicopter is within one rotor span of the ground. It is most apparent when the main rotor disk is within one-half the rotor span of the ground. As in an airplane, ground effect occurs when the ground interferes with the vortices produced at the ends of the main airfoil—in this case, the rotor-tip vortices. The ground also reduces the acceleration of the induced flow—the air pulled down and through the rotor disk. The decreased downward velocity of the induced flow makes a given pitch angle more effective at producing lift. While in ground effect, the helicopter requires less power to hover.

Translating Tendency (Cyclic Rigging)

Helicopters have a tendency to drift in the direction of tail rotor thrust. For example, American-built helicopters tend to drift right in a hover. Manufacturers compensate for this effect by tilting the main rotor mast slightly to the left or by rigging the cyclic slightly to the left. But the pilot may need to apply slight left cyclic pressure to compensate, especially when operating at a high power setting, such as during a hover or while climbing.

Effective Translational Lift (ETL)

A large increase in performance occurs while in forward flight or when hovering in a wind. Air moving horizontally across the rotor disk helps the rotor produce more lift at a given power setting. This effect is generally seen at speeds of 10 to 15 knots. The transition to ETL is marked by a low-frequency vibration. The helicopter's nose rises and the aircraft begins to climb vertically.

Transverse Flow Effect

A decrease in lift in the aft portion of the rotor disk occurs during forward flight or when hovering in a wind. At slow speeds, the air moving through the aft portion of the rotor disk is accelerated for a longer time and moves more vertically than the air at the front of the disk. As this accelerated air flows through the aft portion of the disk, it reduces the angle of attack of the rotor blades, decreasing lift produced by the aft part of the rotor disk.

Dissymmetry of Lift

Dissymmetry of lift is a condition in which the main rotor does not produce lift equally across the entire rotor disk. Dissymmetry of lift is most apparent during a retreating blade stall, in which the left half of the rotor disk (as seen from above) is stalled due to the helicopter's high forward speed, high gross weight, high density altitude, low rotor rpm, turbulence, abrupt use of controls, or steep turns. This effect is present only when the helicopter is in forward flight or hovering in a wind. Designers can compensate for dissymmetry of lift by allowing the blades to flap or feather.

Tuning Flight Simulator for Helicopters

To fly a helicopter in Flight Simulator, it's important that the simulator is running smoothly. The more times your screen is redrawn each second (a measurement known as the frame rate), the smoother motion will appear, and the better the simulation will feel. A frame rate lower than 15 frames per second will make the helicopter extraordinarily difficult to control; the higher the frame rate, the more realistic the simulation.

You can monitor frame rate by pressing SHIFT+Z twice to display Flight Simulator's coordinate data and frame-rate counter in the upper left corner of the screen. The frame rate is displayed in frames per second (FPS).

For more information about frame rates and improving the performance of Flight Simulator, see Optimizing Visuals and Performance.

A Robinson R22 Beta II takes off for a scenic tour of Molokai, Hawaii.

Flight Controls

A helicopter has four basic flight controls:

Collective
Throttle
Cyclic
Antitorque pedals

Helicopters are much more sensitive to control inputs than most aircraft. To fly a helicopter smoothly and precisely, you must coordinate your use of all the flight and power controls. Keep these basic considerations in mind:

Use smooth, small control pressures, not abrupt or large movements that can quickly lead to ever-larger oscillations and rapidly escalate to complete loss of control. You can almost just think what you want to do and the helicopter will do it—that's how little physical force you want to apply to the controls.
Anticipate how moving one control will require corresponding movements of the other controls. For example, if you add power by increasing collective, you must also add left antitorque pedal to compensate for the helicopter's tendency to rotate to the right.
Make sure you understand the special aerodynamic effects unique to helicopters, as well as the proper control inputs needed to compensate for them. You must anticipate these effects, not just react to them. If you wait to experience the effect and then react, you'll have trouble controlling the aircraft.
Never remove your hand from the cyclic while the main rotor is turning.
After landing, make sure the helicopter has firmly settled and that the collective is in the full down position as you prepare to shut down the engine. Hold the cyclic in the neutral position until the main rotor stops.

Helicopter Keyboard Shortcuts

Increase Collective F3

Decrease Collective F2

Increase Throttle CTRL+F3

Decrease Throttle CTRL+F2

Move Cyclic Back Num Pad 2

Move Cyclic Forward Num Pad 8

Move Cyclic Left Num Pad 4

Move Cyclic Right Num Pad 6

Left Antitorque Pedal Num Pad 0

Right Antitorque Pedal Num Pad ENTER

Note: Although you can fly helicopters in Flight Simulator using keyboard shortcuts or a twisting joystick, it's much easier if you have a joystick and rudder pedals (the "stick" of the joystick controls the cyclic; the throttle handle controls the collective).

The Collective

The collective (short for "collective pitch control") serves as a helicopter's primary altitude and power control. It varies the lift produced by the main rotor system by increasing or decreasing the pitch of all the main rotor blades simultaneously or collectively, hence the name of the control. Essentially, the collective determines the size of the thrust vector.

In a real helicopter, you use your left arm to raise and lower the collective by moving a long lever that's mounted on the floor of the cockpit. In Flight Simulator, use the throttle lever or joystick control, or press F3 to increase collective and F2 to decrease collective.

Raising the collective increases the pitch (and therefore the angle of attack) of all of the blades simultaneously, increasing the amount of lift that the main rotor system produces. Lowering the collective decreases the pitch (angle of attack) of all of the blades simultaneously, decreasing the amount of lift that the main rotor system produces.

When you raise the collective, the rotor blades produce more lift. But the increased angle of attack of the blades also produces more drag, so you must add power to maintain rotor rpm. This increase in power causes an equal and opposite reaction, increasing torque. Therefore, when you raise the collective you must also apply the left antitorque pedal. Reducing collective decreases lift, decreases drag, requires less power to maintain rotor rpm, and therefore decreases torque. To maintain coordinated flight, you must apply right pedal pressure as you lower the collective. Remember to anticipate—if you wait to experience the effect of a control movement and then react, you'll have trouble controlling the aircraft.

The Throttle

The throttle is mounted at the end of the collective. In Flight Simulator, both the R22 and the JetRanger III and are equipped with governors that automatically adjust the rotor rpm as the pilot increases and decreases the collective. Power automatically increases when the collective is raised, and decreases when the collective is lowered to ensure that the rotor's rpm remains constant as the blades' angle of attack changes.

To control the throttle independently in Flight Simulator, press CTRL+F2 to decrease power and CTRL+F3 to increase power.

The Most Important Rule of Helicopter Flying: Maintain Rotor rpm!

If the main rotor and tail rotor aren't spinning fast enough, they can't create enough lift, and the result could be catastrophic. Without main rotor lift, a helicopter can't stay aloft; without tail rotor lift, the pilot can't maintain yaw control. Fortunately, both the R22 and JetRanger III feature governors that automatically keep the rpm within acceptable limits.

The Cyclic

During flight, the cyclic (short for "cyclic pitch control") controls the helicopter's pitch and bank attitude like the yoke or stick that controls the elevator and ailerons in an airplane. The cyclic is the primary airspeed control in flight. Applying forward cyclic causes airspeed to increase; aft cyclic reduces airspeed.

You control the direction of the force generated by the rotor disk by tilting it with the cyclic through a series of mechanical linkages. The cyclic tilts the rotor disk and, in a hover, controls the direction and speed of the helicopter's movement across the ground. Moving the cyclic forward makes the helicopter fly forward. Moving the cyclic to the left makes the helicopter translate—move over the ground—to the left, and so forth. The position of the collective determines the size of the thrust vector. The position of the cyclic determines the tilt (or direction) of the thrust vector.

In Flight Simulator, you can control the cyclic with a joystick, or with the numeric keypad on the right side of your keyboard. (Press 2 to move the cyclic back, 8 to move it forward, 4 to move it left, and 6 to move it right.)

The amount you move the cyclic determines how fast the helicopter moves in a particular direction. Moving the cyclic usually requires you to make adjustments with the other flight controls, the collective and the antitorque pedals. For example:

In normal cruising flight, applying forward cyclic causes the helicopter's nose to drop. Airspeed increases and the helicopter descends unless you increase collective to increase the lift produced by the main rotor and add power.
Applying aft cyclic causes the helicopter's nose to rise. Airspeed decreases and the helicopter ascends unless you apply down collective to reduce power.
Moving the collective changes torque, so you must also apply left or right antitorque pedal to maintain coordinated flight.

Antitorque Pedals

You compensate for the torque produced by the main rotor using the antitorque pedals. Increasing collective will cause more torque, decreasing collective will cause less torque. You must use the pedals to avoid spinning out of control.

When you add power by increasing collective, you must use left pedal to keep the helicopter from rotating to the right. Likewise, if you decrease power by lowering the collective, you must use right pedal to compensate for the reduction in torque. (Note that this is the opposite of an airplane's left-turning tendencies at high power settings.)

In forward flight, a helicopter turns just like an airplane: by banking. In a hover, use the pedals to maintain the helicopter's heading—the direction in which the nose is pointing. In a stationary hover, you can also use left or right pedal to turn the helicopter. This type of turn is called a pedal turn.

In cruising flight and during normal climbs and descents, use the pedals to maintain coordinated flight—that is, to keep the helicopter in trim. Do not use the pedals to turn the helicopter except while in a hover. Use the cyclic to bank and turn the helicopter and to maintain the aircraft's heading. You can determine whether the helicopter is in trim by checking the ball in the turn coordinator or turn needle. If the ball is left of center, add left pedal pressure. If the ball is right of center, apply right pedal pressure.

In Flight Simulator, you can use rudder pedals, or you can control the antitorque pedals with a joystick that twists, or with the numeric keypad. (Press 0 for the left pedal, and ENTER for the right.)

Divided Power

A helicopter's engine drives both the main rotor and the tail antitorque rotor. If you must use a high power setting to maintain a hover or to hover in a strong right crosswind, the tail rotor may not be able to develop sufficient thrust to counteract the torque developed by the main rotor or the helicopter's tendency to weathervane into the wind.

Maneuvers

Hovering

Hovering (maintaining a steady position 3 to 5 feet above the ground) is one of the most difficult maneuvers for new helicopter pilots to master. But the hover is one of the most important maneuvers because every takeoff starts with a hover, and every landing ends with one.

Wind further complicates matters. A change in ground speed or airspeed affects the power required to maintain altitude, which affects torque—so anticipate changes and correct for them quickly.

The key is to focus on the horizon and on objects 30 to 50 feet away so that you can sense movement, stop it, and return to the original position.

Taxiing

Taxiing in a helicopter is often called "hover taxiing" because you will hover just a few feet off the ground with a forward motion. Generally, you would use this technique when taxiing from one area to another on the airport, or if you needed to move the helicopter a short distance.

If you lift the skids more than about 3 feet (1 meter) above the ground, the helicopter effectively flies out of ground effect, and you'll need about 10 percent more power to maintain a hover.

Keep in mind that under certain conditions, such as in tall grass, over steep or rough terrain, or at high altitudes, the helicopter may not be able to hover out of ground effect.

Remember:

The cyclic controls the direction in which the helicopter moves.
Use small, smooth adjustments of the collective to maintain the proper altitude.
To keep the nose straight, apply pressure to the left or right antitorque pedal.

Takeoff

Unless obstacles must be avoided, helicopter pilots don't usually make vertical takeoffs straight up into the sky, or fast departures close to the ground. A helicopter that is a few hundred feet above the ground with little airspeed, or close to the ground moving very quickly, will have a difficult time recovering if the engine fails. The recommended procedure is to lift off into a hover a few feet above the ground, and to then accelerate to 40 to 50 KIAS before initiating a slow climb.

Note the wind direction and speed. If possible, plan to take off directly into the wind to minimize sideways drift and to increase the helicopter's performance during takeoff and climb. Wind blowing through the main rotor disk has the same effect as forward airspeed. For example, if the helicopter is facing into a 10- to 15-knot wind, the rotor experiences effective translational lift even when the aircraft is on the surface.

When you're ready to lift off, use scenery objects as a guide. Note a point in the distance (such as a building, tower, or gas pump). Use that point and the outside horizon as references to help you maintain the helicopter's alignment and attitude as you lift off.

Set the cyclic (joystick handle) in an approximately neutral position. Set the collective in the full down position (use the joystick throttle, or press F2).

Smoothly and slowly raise the collective (press F3, or push forward on the joystick throttle). The helicopter should become light on the skids. As the helicopter's weight comes off the skids, it will start to drift and turn to the right. Hold the collective steady at this point, and use slight left cyclic pressure to hold the helicopter in position. Apply left pedal pressure (twist the joystick to the left, press the left rudder pedal, or press 0 on the numeric keypad) to compensate for the torque from the main rotor.

Keep your attention outside the helicopter, and focus on the horizon and other visual clues. To continue the liftoff, smoothly increase the collective. Anticipate the need to add left pedal as you lift off and make small, smooth corrections with the cyclic and pedals to maintain heading and position.

Hold the helicopter skids about 3 feet (1 meter) above the ground. You want to stay low in case the engine fails and to keep the helicopter in ground effect. Raise or lower the collective to maintain altitude. Maintain the correct attitude using light, small cyclic pressures, and use the antitorque pedals to keep the helicopter's nose from rotating. Anticipate corrections to compensate for wind. You'll need slight forward cyclic pressure if you take off into a headwind, left pressure with a left crosswind, and so forth.

When you're ready to continue the takeoff, gently apply a small amount of forward cyclic to lower the nose and begin moving forward along the departure path. The helicopter may tend to settle as you start forward. Compensate by adding slight upward collective.

As airspeed reaches 10 to 15 knots, the helicopter enters the effective translational lift phase. The nose tends to yaw left and pitch up slightly. Apply some forward cyclic to prevent the nose from rising. Add some left lateral cyclic to prevent the helicopter from drifting right, and apply right pedal pressure to maintain heading. The helicopter will continue climbing and accelerating. If you feel like you're juggling a lot at this point, you are; helicopter flying is not easy, and it's been described as an activity similar to trying to balance one ball on top of another.

Continue the takeoff by flying a modified traffic pattern. Climb straight ahead at 60 knots to 300 feet (90 meters). The helicopter should be in a nearly nose-level attitude.

Turn 90 degrees left (standard traffic pattern) or right to the crosswind leg. Maintain 60 knots indicated airspeed and continue the climb to 500 feet (150 meters).

To accelerate and maintain the helicopter's rate of climb, increase collective and add slight forward cyclic. On the crosswind leg, depart the traffic pattern or return for another landing by turning 90 degrees again to join the downwind leg.

Climb

Both the R22 and the JetRanger can climb at over 1,300 feet per minute (at sea level under standard weather conditions). Climbs are usually performed at 60 KIAS in both helicopters.

For a normal climb, adjust the collective (use the joystick throttle, or press F3) for a manifold pressure (R22) or torque (JetRanger) setting about 10 percent above that required to maintain a hover in ground effect.

Use the cyclic (the joystick or the ARROW keys) to set a pitch attitude that maintains an airspeed of about 60 knots.

Note that as you climb, the engine produces less power. Monitor the engine instruments and smoothly add collective to maintain climb power as your altitude increases.

Keep the following considerations in mind as you climb:

Use the collective to control power and the rate of the climb.
Monitor engine instruments closely to ensure that you stay within operating limits.
Maintain attitude (and thus airspeed) by looking out to the horizon. Focusing on a point too close to the nose makes it difficult to maintain the proper aircraft attitude.
Use the cyclic to control airspeed (and the helicopter's attitude) and the antitorque pedals to maintain heading or to establish a crab angle as necessary to fly a constant ground track.
Use the antitorque pedals to maintain trim (coordinated flight). A slip or skid severely degrades climb performance.

To level off from a climb, start decreasing collective about 50 feet (15 meters) below the altitude at which you want to level off. Add right antitorque pedal as you decrease power to the cruise setting. Use the cyclic to maintain cruising airspeed. Apply forward cyclic to increase speed and aft cyclic to slow down.

Cruise

Under typical conditions in the R22, you should set the collective between 21 and 22 inches of manifold pressure for cruise. In the JetRanger, set 80 percent torque.

To maintain the desired track over the ground, use the antitorque pedals to turn the helicopter into the wind and establish the correct crab angle. To turn, use the cyclic to bank the helicopter.

Use the antitorque pedals to keep the helicopter in trim—that is, in coordinated flight. If the inclinometer in the turn coordinator shows a slip or a skid, apply left or right pedal pressure as necessary to center the ball.

Descent

To descend at a comfortable rate without building too much speed, you must decrease main rotor pitch by lowering the collective. Anticipate the need for the right antitorque pedal as you decrease power.

The nose drops as you lower collective, so remember that you'll need to add a little aft cyclic to maintain the correct pitch attitude and airspeed. Don't add too much aft cyclic, however, or the aircraft will climb.

Note that as you descend, the engine produces more power. Monitor the engine instruments and smoothly reduce collective to continue your descent.

To level off from a descent, start increasing collective about 50 feet (15 meters) above the altitude at which you want to level off. Add left antitorque pedal as you increase power, and use the cyclic to maintain cruising airspeed. Apply forward cyclic to increase speed and aft cyclic to slow down.

Approach

Approaches in a helicopter have more to do with local traffic and terrain than a need to be at a target speed and configuration. Enter the airport traffic area in a safe manner that avoids obstacles, and follow the landing procedures as described.

Landing

To land, reverse the procedure for a normal takeoff. That is, fly an approach from a 500-foot (150-meter) traffic pattern, enter a hover at about 3 feet (1 meter) above the ground, and then slowly and smoothly lower the aircraft to the ground.

Following this procedure helps you establish good habits and makes it easier to achieve smooth, consistent landings.

To land a helicopter

Review the Landing checklist on the Kneeboard.
Fly a modified traffic pattern that avoids the flow of fixed-wing traffic.
During the first half of the approach, decrease power by lowering the collective. During the second half of the approach, you must smoothly increase power to arrive at the 3-foot (1-meter) hover just as you set hover power.
Fly the downwind leg at 500 feet (150 meters) at 100 knots.
Turn to the base leg, decelerate to 70 knots, and then descend to 300 feet (90 meters).
Turn final at 300 feet (90 meters), and decelerate to 52 to 60 knots.
A descent angle of 10 to 12 degrees provides good obstacle clearance and helps you keep the landing area in sight.
Adjust the collective to control the helicopter's rate of descent. Increase collective to reduce the rate of descent; decrease collective slightly to increase rate of descent.
Use the cyclic to adjust the rate of closure with your landing spot. Apply slight aft cyclic to reduce the rate of closure; forward pressure increases the rate of closure. The ideal forward rate of travel is that of a normal walk.
Continue the approach until the rate of closure with the landing spot accelerates. Begin dissipating forward speed by applying smooth, slight back pressure on the cyclic. As you decelerate, anticipate the need to decrease collective to maintain altitude.
As airspeed drops to 10 to 15 knots, the aircraft will lose effective translational lift. You must raise the collective to compensate for the loss of lift. You'll also need to add left antitorque pedal pressure as you increase collective pitch.
Transition to the hover over the landing spot. Enter a 3-foot (1-meter) hover over the spot where you want to land. Slowly lower the collective and allow the helicopter to settle onto the landing spot. Once the aircraft is down, lower the collective all the way.

Autorotation

Autorotation in a helicopter is the equivalent of a power-off glide in an airplane; it's how you land after an engine failure.

During autorotation, it's important to maintain rotor rpm so you have lift available to cushion the landing. You must also maintain the correct forward speed so that you can reach a suitable landing area and flare to reduce the rate of descent before ground contact.

To learn more about autorotation, see the Robinson R22 Beta II and Bell 206B JetRanger III flight notes.

Getting Technical

To learn more about helicopters and flying them, see the Suggested Reading section below. Here's a taste of what else you can learn.

Hazardous Conditions

Helicopter pilots must be aware of several hazardous conditions that they may encounter. The following situations require immediate and correct responses to avoid loss of control. (Engine failure, tail rotor failure, and blade stall caused by low rotor rpm also require immediate corrective action.)

Retreating Blade Stall

In a retreating blade stall, the rotor blades on the left side of the rotor disk (when seen from above) exceed their critical angle of attack, and stall. This situation can occur when a helicopter is flying at a high forward speed, which increases the angle of attack of the rotor blades moving toward the rear of the aircraft. This phenomenon is the primary limitation on a helicopter's maximum speed. Turbulence, low rotor rpm, steep and abrupt turns, high gross weight, and high density altitude can also induce retreating blade stall.

The signs of retreating blade stall include a low-frequency vibration, a tendency for the helicopter's nose to pitch up, and a roll to the left. To recover from a retreating blade stall, lower the collective to reduce the rotor's angle of attack and slow down.

Settling with Power

Helicopters have a tendency to descend rapidly into their own rotor downwash. The high descent rate associated with settling with power is the most common cause of helicopter accidents. Settling with power occurs when the helicopter has an airspeed of less than 10 knots, is in a descent of more than 300 fpm, and is developing more than 20 percent power.

Most often you encounter these conditions while hovering out of ground effect without maintaining altitude, when attempting to hover above the helicopter's out-of-ground-effect hover ceiling, or during a landing with a tailwind, which blows the downwash beneath the helicopter.

This phenomenon is caused by vortices that form at the root of the rotor blades and then travel outward. Like a stalled airplane wing, the rotors no longer produce enough lift to maintain the helicopter in level flight or a gradual descent. Settling with power is usually associated with a low-frequency vibration, loss of cyclic control effectiveness, and a rapid descent rate.

To recover, you must move the helicopter out of its downwash by traveling forward, backward, or to the side at an airspeed of at least 10 knots.

Low-G Condition

This situation develops whenever there is less than 1G (the weight of the helicopter) on the rotor disk. The pilot can induce a low-G situation by making abrupt cyclic control inputs, flying through turbulence, or when pushing over from a steep climb. In this situation, the nose drops and the aircraft may roll rapidly to the right because the tail rotor is above the main rotor disk and producing thrust to the right. The main rotor may hit the tail boom, and helicopters with semirigid rotor systems may experience mast bumping. Either effect may cause loss of the main and tail rotors.

To recover from a low-G situation before you lose control, gently apply aft cyclic to raise the nose and add Gs to the rotor disk. Apply left cyclic to counteract the tendency to roll to the right.

Rotor Systems

Most modern helicopters have one of three types of main rotor systems:

Semirigid
Fully articulated
Rigid

Semirigid

A semirigid rotor system has two main rotor blades. The blades flap—move up and down—as a unit, like a teeter-totter, to compensate for dissymmetry of lift. They also feather—twist at the rotor hub—as a unit to adjust angle of attack as they rotate. The rotor system is also underslung to compensate for the Coriolis effect: the leading and lagging of the main rotor blades as the center of mass moves toward and away from the rotor's axis of rotation.

Semirigid rotor systems are relatively inexpensive to maintain, but their flapping characteristics can lead to mast bumping (the main rotor hub makes contact with the main rotor mast). They are also susceptible to low-G conditions.

Both the Robinson R22 Beta 2 and the Bell 206B JetRanger III in Flight Simulator have semirigid rotor systems. The R22 has a relatively low-inertia rotor system, making it easy to recover from low rotor rpm situations. The JetRanger system has relatively high inertia: the rotors lose and build rpm more slowly than helicopters with lighter rotor systems like the R22. This high inertia is an advantage during autorotation and some other maneuvers, but it can cause problems if you need to apply power quickly.

Fully Articulated

A fully articulated rotor system has three or more main rotor blades. The blades flap—move up and down—independently to compensate for dissymmetry of lift. They also feather—twist at the rotor hub—independently to adjust angle of attack as they rotate, and lead and lag independently to compensate for the Coriolis force.

Fully articulated rotor systems are more expensive to manufacture and maintain than semirigid rotors, but they are less susceptible to low-G conditions and mast bumping. However, they are more greatly affected by ground resonance.

Rigid

A rigid rotor system has three or more main rotor blades. The blades flap—move up and down—independently to compensate for dissymmetry of lift. They also feather—twist at the rotor hub—independently to adjust angle of attack as they rotate. Unlike a fully articulated system, a rigid rotor system is hingeless and the rotors can lead and lag independently.

Rigid rotor systems are the most expensive types of rotors to manufacture. They are typically made of composite materials and titanium, and tend to give a relatively rough ride. However, they resist low-G conditions and ground resonance and require less maintenance than other rotor systems.

Beyond North America

The information in this article assumes that the aircraft's main rotor turns left, or counterclockwise, when viewed from above. Helicopters manufactured in the United States are equipped with this type of main rotor. However, many helicopters made elsewhere in the world have main rotors that turn to the right, or clockwise, when viewed from above. If you are flying a real-world helicopter manufactured outside the U.S., you may need to reverse the pedal inputs and some cyclic inputs described in these topics.