Tutorial for the First Flight of a Multi-rotor Aircraft

Introduction to Flight Mode

This article provides an overview of the flight modes of multi-rotor aircraft.

Overview

Multi-rotor (helicopter) systems feature a total of 23 built-in flight modes, 10 of which are commonly used; each mode offers distinct flight characteristics and functions.

Flight modes can be controlled via the remote controller, mission commands, a Ground Control Station (GCS), or an onboard companion computer.

Both the remote controller and the ground station can control flight modes simultaneously, with the system typically prioritizing the most recent command received.

Mode	Altitude Control	Attitude Control	GPS Positioning	Notes Summary
Acro	–	–		Maintains attitude, no horizontal self-leveling
Airmode	–	-/+		Not actually a flight mode but a function; see below
Alt Hold	s	+		Maintain altitude and automatically adjust level & pitch
Auto	A	A	Y	Execute pre-defined missions
Autonomous Autorotation	A	A	Y	Emergency function for traditional helicopters. Helicopter only; SITL only for now
AutoTune	s	A	Y	Automatically tune PID parameters
Brake	s	A	Y	Bring vehicle to an immediate stop
Circle	s	A	Y	Orbit around a point
Drift	–	+	Y	Similar to stabilize mode, allows yaw adjustment
Flip	A	A		Climb and perform automatic flip
FlowHold	s	A		Position control based on optical flow
Follow	s	A	Y	Follow another vehicle
Guided	A	A	Y	Navigate to a single point specified by GCS
Land	A	s	(Y)	Land on the ground
Loiter	s	s	Y	Maintain altitude and position; move based on GPS
PosHold	s	+	Y	Maintain altitude and position; manual roll & pitch when stick is off-center (faster movement speed)
RTL	A	A	Y	Return to home location above takeoff point; includes landing for multicopters
Simple/Super Simple			ÿ	Auxiliary flight mode function, pilot’s perspective instead of vehicle heading
SmartRTL	A	A	Y	Similar to RTL, returns home by retracing historical flight path
Sport	s	s		Maintain altitude; keep pitch and roll when sticks are centered
Stabilize	–	+		Automatically maintain pitch and roll
SysID	–	+		Special diagnostic/system identification mode
Throw	A	A	Y	Maintain attitude after being thrown
ZigZag	A	A	Y	Similar to AB point mode, still under development

Symbol	Altitude Control
–	Manual
+	Manual control with limits and self-leveling
S	Pilot-controlled climb rate
A	Automatic control

Recommended flight modes

Generally, when using APM: Copter for the first time, you should progress through the following flight modes in order, ensuring you have mastered each one before moving on to the next:

Stabilize
Alt Hold (Altitude Hold)
Loiter (Hover mode)
RTL (Return-to-Launch)
Auto (Automatic waypoint flight; requires GPS)

Other flight modes:

Acro (Acrobatic mode; no flight controller stabilization assistance)
AutoTune (Automatically fine-tunes settings if the aircraft drifts significantly)
Brake (Locks the aircraft in position, ignoring remote control stick inputs)
Circle (Orbits a point of interest)
Drift
FLIP
FlowHold (Position hold using optical flow)
Guided_NoGPS (Guided mode without requiring GPS)
Land
PosHold (Position hold)
Sport
Throw (Launch by tossing the drone into the air; it automatically stabilizes and takes off)
Follow (Follows another device)
Follow Me (Drone follows you; requires GPS and a mobile ground station)
Simple and Super Simple modes
Smart RTL (Smart Return-to-Launch)
RTL (Return-to-Launch)
SysID (System Identification)
ZigZag
Avoid_ADSB (Manned aircraft avoidance based on ADS-B; requires an external ADS-B module)
Most remote controllers have only one three-position switch, limiting configuration to three modes. To set up six modes, switch mixing can be used.

Flight modes requiring GPS:

Some flight modes rely on GPS for operation; you can check the status lights or the ground station to see if a GPS lock has been acquired.

The following flight modes require a GPS lock to arm and fly:

Loiter
RTL (Return-to-Launch)
Auto
Guided
Drift
PosHold
Follow (following another vehicle)
Follow Me
Circle
Throw
Smart RTL

Flight mode that does not rely on GPS lock:

Stabilize Mode
Alt Hold Mode
Acro Mode
Sport Mode
Land Mode
SysID (System ID)

List of all modes:

Acro (Acrobatic mode; no flight controller stabilization assistance)
Alt Hold (Altitude Hold mode)
Airmode
Auto (Automatic mode: executes predefined missions)
AutoTune (Automatic fine-tuning; corrects significant drift or imbalance)
Brake (Brake/Lock mode; locks the aircraft in position, ignoring stick inputs)
Circle (Circles around a point of interest)
Drift
FLIP
Flowhold (Position hold using optical flow)
Follow (Follows another device)
Follow Me (Drone follows the user; requires GPS and a mobile ground station)
Guided (Guided mode; does not require GPS)
Land
Loiter
PosHold (Position Hold mode)
Sport
Throw (Throw-to-launch mode; drone stabilizes and takes off automatically after being tossed)
Simple and Super Simple modes
Smart RTL (Smart Return-to-Launch)
RTL (Return-to-Launch)
SysID (System Identification)
ZigZag
Avoid_ADSB

Stabilization Mode

Overview:

The pilot uses the roll and pitch controls to adjust the aircraft’s tilt angle; when the sticks are released, the aircraft automatically levels itself.
In windy conditions, the pilot must constantly make roll and pitch corrections to maintain a stationary hover.
The pilot uses the yaw control to manage the rate of rotation; when the yaw stick is released, the aircraft maintains its current heading.
Throttle input controls average motor speed, so the pilot must constantly adjust it to maintain altitude.
Throttle input is automatically adjusted based on the aircraft’s tilt angle (e.g., increasing throttle when the tilt is excessive) to compensate for altitude changes caused by tilting the aircraft.
Warning: Mastering flight in Self-Leveling Mode is essential before attempting other flight modes. Pilots should be able to quickly switch back to Self-Leveling Mode in an emergency to prevent accidents.

Debug:

ANGLE_MAX controls the maximum tilt angle; the default is 4500, representing 45° (the system automatically locks if this angle is exceeded).
ANGLE_RATE_MAX controls the maximum roll and pitch rotation rates of the aircraft; the default is 18000, representing 180°/second.
ACRO_YAW_P controls the helicopter’s rotation speed based on the pilot’s yaw input. With the yaw stick held fully left or right, the default value of 4.5 results in a rotation speed of 200°/second. Higher values will cause it to rotate faster.
Stabilize Roll P and Pitch P control the helicopter’s roll and pitch response to pilot input, as well as the correction applied to the error between the desired and actual angles. The default value of 4.5 commands a rotation rate of 4.5°/second for every 1 degree of angular error. Higher gains (e.g., 7 or 8) provide faster response times and better wind resistance.
A lower Stabilize P value will cause the helicopter to rotate very slowly, potentially making it feel unresponsive and increasing the risk of a crash if disturbed by the wind. If smoother flight is desired, try lowering the RC_Feel parameter before reducing the Stabilize P value.

The higher the P value, the faster the aircraft’s correction and response speed; however, an excessively high P value will cause high-frequency oscillation.

The Rate Roll/Pitch P, I, and D terms control the motor output based on the target rotation rate requested by the outer-loop stabilizer (i.e., the angle controller). These values are typically related to the helicopter’s power-to-weight ratio; helicopters with higher power require lower rate PID values. For instance, a high-thrust helicopter might use a Rate Roll/Pitch P-value of 0.08, whereas a lower-thrust model might use 0.18 or higher.
The Rate Roll/Pitch P-value is the single most important parameter to tune correctly for the helicopter.
A higher P-value results in a more aggressive motor response to achieve the desired rotation rate.
For a standard helicopter, the default P-value is 0.15.
The Rate Roll/Pitch I-term compensates for external forces that would otherwise prevent the helicopter from maintaining the desired rate over time.
A high I-term will ramp up quickly to maintain the target rate and drop rapidly to prevent overshoot.
The Rate Roll/Pitch D-term dampens the helicopter’s response as it accelerates toward the target setpoint.
An excessively high D-value can cause unusual vibrations and a “memory” effect, making the controls feel sluggish or unresponsive. A properly set-up controller should typically allow for a D-value of 0.011.
Depending on the specific model, the value generally falls between 0.001 and 0.02.

Verify performance using DataFlash logs.

The best way to evaluate Stabilize mode performance is to download the dataflash logs from the flight, open them in Mission Planner, and plot the relationship between Roll-In (or DesRoll—the pilot’s desired roll angle) and Roll (actual roll), as well as between Pitch-In (or DesPitch—the desired pitch angle) and Pitch (actual pitch), based on the ATT messages.

Frequently Asked Questions

The new helicopter flips immediately after takeoff. This is usually caused by incorrect motor sequencing, wrong motor direction, or the use of the wrong propellers (clockwise vs. counter-clockwise). You should first check the hardware connections and then verify the firmware type. The helicopter oscillates on the roll or pitch axis. This usually indicates an incorrect “Rate P” value. See the “Tuning” section above for tips on adjusting these gains.
The helicopter oscillates during rapid descent. This occurs because the helicopter is falling into its own prop wash; while increasing the “Rate Roll/Pitch P” value might help, it is nearly impossible to tune this out completely.
The helicopter yaws 15 degrees to the left or right upon takeoff. Some motors may not be mounted straight, or the ESCs may not be calibrated.
The helicopter consistently drifts in one direction, even in calm conditions. Try using SaveTrim or AutoTrim to level the helicopter.
The helicopter fails to maintain altitude or remain perfectly stationary in the air. As mentioned above, this is a manual flight mode; maintaining altitude and position requires constant stick input.
Occasional rolling or pitching. This is usually caused by interference with the receiver (e.g., FPV equipment placed too close to the receiver) or ESC issues, which can often be resolved by calibrating the ESCs.
Sudden flipping or tumbling during flight. This is almost always caused by a mechanical failure of a motor or an ESC.

Altitude Hold Mode (AltHold)

In altitude hold mode, the flight controller automatically maintains the current altitude while allowing manual control of roll, pitch, and yaw.

Overview:

When Altitude Hold (AltHold) mode is active, the drone automatically controls the throttle to maintain its current altitude, while roll, pitch, and yaw controls operate the same way as in Stabilize mode.

By default, altitude-hold mode relies on fused data from the barometer and accelerometer; excessive flight vibration may result in suboptimal altitude-hold performance. If you have installed an altimeter (such as an ultrasonic or laser sensor), please verify that the hardware is functioning correctly.

How to control:

The rate of ascent and descent of the aircraft can be controlled using the throttle stick.

When the throttle is maintained at the mid-range (40%–60%), the flight altitude remains constant.
Outside this range, the aircraft will ascend or descend at a rate determined by the throttle input. The maximum ascent and descent rate is 2.5 m/s, a limit defined by the flight parameter PILOT_VELZ_MAX.

In altitude hold mode, AC3.1 and later versions feature two states: unlocked and locked. When the aircraft is in the locked state, it must remain stationary for a few seconds before it can be unlocked; this allows the internal circuitry to detect and indicate that the aircraft has landed.

Hyperparameter tuning:

Under the Altitude Hold option, the P variable is used to convert altitude error (the difference between desired and actual altitude) into the desired rate of ascent or descent. A higher P value results in stronger altitude-holding capability, but setting it too high can cause throttle instability.

The “Throttle Rate” option is used (though typically requires no modification) to convert the desired ascent or descent rate into the corresponding acceleration.

The throttle acceleration PID controller measures the error between the required acceleration and the actual motor acceleration. If the P and I values are modified, the ratio P: I should be maintained at 1:2 (i.e., the I value should be twice the P value). These values should not be increased; for very powerful aircraft, reducing them by 50% may yield better results (e.g., a P value of 0.5 and an I value of 1).

Verifying altitude-hold performance through flash log analysis:

Download a Dataflash log and manually analyze it via the Ground Station (Log Overview and Analysis – Dataflash Logs).

APM AC3.1: Plot CTUN fields BarAlt (barometric altitude), WPAlt (target altitude), and RelAlt (Inertial Navigation altitude estimate).

APM AC3.2 / Pixhawk (running AC3.1 or AC3.2): Plot CTUN fields BarAlt (barometric altitude), Alt (altitude), and Alt (Inertial Navigation altitude estimate).

Check these three options as shown below.

Frequently Asked Questions:

When using altitude hold mode, severe vibration can cause the aircraft to rise rapidly. Visit the Wiki page to learn more about detecting and reducing vibration.
The aircraft slowly descends or ascends until it stabilizes. This is usually caused by the throttle stick not being in the center position. It typically happens when switching from a manual flight mode (such as Stabilize mode) to altitude hold mode without centering the stick for a hover. Please refer to…
The motors pause briefly when altitude hold is engaged, then quickly return to normal operation. This usually occurs when entering altitude hold mode during a rapid climb. The target altitude is set at the moment of switching; if the aircraft is rising too fast, it overshoots the target position. The altitude controller then applies a “hard brake” to decelerate until the aircraft returns to the target altitude. The solution is to engage altitude hold mode only when the aircraft is stable.
Changes in air pressure can cause the aircraft to drift up or down by several meters for an extended period, or result in inaccurate altitude readings on the ground station—including occasional negative altitude values (i.e., altitude lower than the “Home” position).
During high-speed forward flight, the displayed altitude momentarily drops by 1–2 meters after exceeding the target altitude. This is due to aerodynamic effects creating a momentary low-pressure zone around the flight controller; the altitude hold system interprets this as an upward climb and executes a descent command to compensate. There is currently no definitive fix; while increasing the `INAV_TC_Z` parameter to 7 (default is 5) can reduce the impact, it may trigger the common issue described in #1 above.
Altitude hold performance becomes unstable when the aircraft is close to the ground or landing. This may be caused by pressure fluctuations resulting from propeller wash. The solution is to isolate the flight controller from propeller wash or protect it within a properly ventilated enclosure.

Sufficient power margin:

Adequate power is crucial; this depends on factors such as battery discharge capability and the matching of the motor, ESC, and propellers. A poor configuration can result in sluggish flight performance.

Ideally, the aircraft should hover at around 50% throttle; requiring more than 70% throttle indicates insufficient power, which is dangerous.

Warning: Configuring a throttle curve (e.g., to flatten the response in the mid-range) will increase the dead zone for the altitude-hold throttle level.

FlowHold Mode

FlowHold mode uses an optical flow sensor to maintain position without requiring GPS or downward-facing LiDAR.

Note: FlowHold is available in Copter-3.6 (and later versions).

FlowHold mode is similar to PosHold mode; the pilot can directly control the vehicle’s tilt angle using the roll and pitch sticks. When the pilot releases the sticks, the autopilot uses optical flow to maintain a hover.

In this mode, optical flow data is used to estimate the vehicle’s altitude relative to the ground and its flight speed; the flight controller does not use LiDAR data. Shortly after takeoff or following significant changes in altitude, the vehicle may wobble while acquiring new velocity readings.
The following parameters can be used to tune FlowHold performance:

FHLD_BRAKE_RATE: Controls the deceleration rate when the pilot releases the sticks.
FHLD_FILT_HZ: Filter applied to the optical flow sensor data.
FHLD_FLOW_MAX: Maximum speed (in m/s) used when the optical flow sensor is active.
FHLD_QUAL_MIN: Minimum flow quality threshold; if the flow sensor quality drops below this value, FlowHold reverts to AltHold behavior.
FHLD_XY_P, FHLD_XY_I, FHLD_XY_IMAX, and FHLD_XY_FILT_HZ: Parameters used to tune the stopping response.

Loiter Mode

Overview:

When Loiter mode is activated, the aircraft automatically maintains its current position, heading, and altitude.

GPS positioning, compass interference, and vibration all directly affect hovering performance.

How to control:

The operator uses the remote controller’s sticks to control the aircraft’s horizontal position and vertical altitude.

Horizontal position is adjusted using the Roll and Pitch sticks; the default maximum horizontal speed is 5 m/s (see “How to Configure” below). When the pilot releases the sticks, the aircraft gradually decelerates until it comes to a stop.

As with Altitude Hold mode, altitude is controlled via the throttle stick.

Heading is controlled via the Yaw stick.

In AC3.1 (or later versions), the aircraft can be armed in Loiter mode once a 3D GPS lock is achieved and the HDOP drops to 2.0 or lower.

When a 3D lock is achieved, the LED on the Pixhawk turns green.

In Mission Planner, double-click the “Quick Screen” area and select “gpshdop”; the HDOP value will be clearly displayed in the corresponding box on the right.

How to debug:

Loiter mode incorporates the altitude control found in AltHold mode.

In Loiter mode, the maximum horizontal speed of the aircraft can be adjusted via the “Loiter Speed” parameter (also known as `WPNAV_LOIT_SPEED`) found in the **Config/Tuning > APM:Copter Pids** interface. The unit is cm/s; for example, a value of 500 corresponds to 5 m/s. The maximum horizontal acceleration in Loiter mode is always half of the Loiter speed.

The P-term of the Loiter PID controller (located in the top-right corner of the screen) corrects deviations in horizontal velocity (errors between the target position and the actual position). The default settings are usually sufficient.

The Loiter PID proportional gain converts the desired velocity into the acceleration required to reach the target. It first translates the desired acceleration into a tilt angle and then accelerates using the same angle controller found in Stabilize mode. The default settings are usually sufficient.

Analyzing Loiter mode performance from flash logs:

downloading a dataflash log

Examine the NTUN graph data: compare the DesVelX curve with the VelX curve, and the DesVelY curve with the VelY curve. When the aircraft is performing well, the actual velocity and desired velocity curves appear as shown in the figure below. X = Latitude (positive = North, negative = South); Y = Longitude (positive = East, negative = West).

Display HDOP in Mission Planner

You can make the HDOP value clearly visible by double-clicking the Quick Screen in Mission Planner and selecting “gpshdop” from the large grid of checkboxes.

Frequently Asked Questions

1. If the aircraft descends unusually slowly after the pilot releases the control sticks, this can be resolved by increasing the values for `WPNAV_LOIT_MAXA` (try 500), `WPNAV_LOIT_MINA` (try 100), and `WPNAV_LOIT_JERK` (try 4000).

2. If the aircraft circles, the issue is usually caused by the compass—most likely magnetic interference from power cables located beneath the flight controller. Running the `compassmot` command to test the compass (see: http://copter.ardupilot.cn/wiki/ac_compasssetupupadvanced/#Compassmot_8211_compensation_for_interference_from_the_PDB_ESC_motors) or purchasing a GPS+compass module can typically resolve the problem. Other possibilities include incorrect compass offsets resulting from the calibration process or an incorrect compass orientation.

3. The aircraft flies in the wrong direction immediately upon entering Loiter mode. The cause is the same as in point #2, but the compass error exceeds 90 degrees. Please try the suggestions mentioned above to resolve this issue.

4. The aircraft hovers normally but suddenly flies erratically. This is usually caused by GPS glitches (short-duration signal interference). Since it is impossible to guarantee 100% immunity to this, the pilot should always be prepared to take manual control. It is important to ensure an appropriate GPS HDOP value before takeoff; additionally, lowering the `GPSGLITCH_RADIUS` and/or `GPSGLITCH_ACCEL` parameters allows for more frequent detection of such glitches.

Return-to-Home Mode

In Return to Launch (RTL) mode, the aircraft flies from its current position to a point above the home location and hovers. The behavior of RTL mode is controlled by several adjustable parameters.

Overview:

When switching to Return-to-Home (RTH) mode, the aircraft returns to the “home” point. By default, before returning, the aircraft first ascends to an altitude of at least 15 meters; if the current altitude is higher, it maintains that altitude.

Return-to-Launch (RTL) relies on GPS; therefore, a GPS lock must be established before attempting to use this mode. Before arming, ensure the APM’s blue LED is solid (not flashing). For GPS units without a compass, the blue LED turns solid once a GPS lock is acquired. For GPS+compass modules, the blue LED flashes once a GPS lock is acquired.

RTL commands the aircraft to return to the “home” point—specifically, the location where it was armed. Consequently, the “home” point should always be the actual GPS takeoff location, free of obstacles and away from crowds. With APM: Copter, if a GPS lock is acquired before arming, the “home” point is set to the location where the aircraft is armed. This means that if you trigger RTL, the aircraft will return to the spot where it was armed.

Note:

In RTL mode, the flight controller uses a barometer to measure air pressure and determine altitude (“pressure altitude”). If the air pressure in the flying area changes, the aircraft will adjust its altitude based on the pressure (rather than actual altitude)—unless you have installed and enabled a sonar sensor for flight within 6 meters of the ground.

Options (user-adjustable parameters)

RTL_ALT: The minimum altitude the vehicle maintains before returning to the launch point.

Set to zero to return at the current altitude.
The return altitude can be set between 1 and 8,000 cm.
The default return altitude is 15 meters (1,500 cm).

RTL_ALT_FINAL: The altitude the vehicle reaches during the final stage of the return or after completing a mission.

Set to zero to have the vehicle land automatically.
The final return altitude can be adjusted between 0 and 1,000 cm.

RTL_LOIT_TIME: The duration (in milliseconds) the vehicle hovers above the “home” point before the final descent.

The hover time can be adjusted between 0 and 60,000 milliseconds.

WP_YAW_BEHAVIOR: Determines how the autopilot controls yaw during missions and return-to-launch (RTL) operations.

0 = Never change yaw.
1 = Point nose toward the next waypoint, or toward the “home” point during RTL.
2 = Point nose away from the next waypoint, or away from the “home” point during RTL.

LAND_SPEED: The descent speed during the final landing phase, in centimeters per second.

The landing speed is adjustable between 20 and 200 cm/s.

Note:

Other navigation settings also affect RTL mode:

WPNAV_ACCEL
WPNAV_SPEED_DN
WPNAV_SPEED_UP

To use RTL, a GPS lock is required (indicated by solid blue GPS and APM LEDs) to establish the “home” point or takeoff location before arming and taking off.

Note that for UBLOX GPS modules, the LED is off while searching for satellites and flashes once a lock is acquired.

Landing and re-arming the vehicle resets the “home” point—a great feature when flying at a field.

If a GPS lock is acquired for the first time while in flight, the “home” point is set to the location where the lock was obtained.

If RTL_ALT is set to a value other than 0, the vehicle will climb to and maintain this altitude during the return flight.

RTL uses WPNAV_SPEED to determine the return speed.

Once the vehicle reaches the “home” point, it enters Loiter mode, waits for the duration specified by AUTOLAND, and then descends to land.

To abort the automatic landing, simply switch flight modes using your transmitter to clear the landing timer and resume normal flight.

During the return flight or while hovering over the “home” point, the throttle stick controls altitude rather than directly controlling motor speed.

Automatic mode

In automatic mode, the aircraft controls its movements according to an internal mission script; this script can consist of a set of waypoints or involve complex actions such as takeoff, rotating a specified number of times, taking photos, and so on.

Auto mode relies on GPS; since mission scripts depend on GPS for positional data, a GPS lock must be established before arming and takeoff. Ensure the LEDs on the autopilot and GPS module indicate that the GPS has successfully locked:

The blue LED on the APM is solid (constantly lit).
The blue LED on the GPS module is solid (constantly lit).
The LED on the GPS+Compass module is flashing.

Notice:

In Auto mode, the flight controller primarily uses a barometer to measure air pressure and determine altitude (“pressure altitude”). If the air pressure changes in your flying area, the aircraft will adjust its altitude based on air pressure rather than true altitude (unless you have installed and enabled a sonar sensor for flight within 6 meters of the ground).

Using Auto Mode on the Ground and in the Air

There are two ways to enter Auto mode: while airborne or while on the ground. If you wish to take off using Auto mode from the ground, a special safety mechanism prevents the mission script from executing until you arm the aircraft and raise the throttle for the first time. This prevents the aircraft from taking off if the mode switch is accidentally bumped. When taking off in Auto mode from the ground, the throttle value from your last altitude-hold flight serves as the baseline for throttle control. Once airborne, the aircraft will fly to the first target altitude and then begin executing the mission script.

Switching to Auto mode while already airborne causes the aircraft to fly to the first target altitude and then begin executing the current mission script.

Tuning

The `Waypoint_Speed` value sets the flight speed between two waypoints.

The default speed between waypoints is 6 meters per second.

`NAV_PI` is used to maintain the desired flight speed between waypoints.

`NAV_P` controls the rate at which the aircraft tilts to achieve the desired speed—determining how quickly it accelerates or how it responds to speed deviations.

A higher P value results in a greater tilt angle.

`Nav_I` compensates for external forces that prevent the aircraft from reaching the desired speed.

A high I value allows the aircraft to reach the desired speed quickly and decelerate rapidly to avoid overshooting.

Ending the Mission

Once the mission script is complete, the aircraft will not return to the “home” point; instead, it will hover at the location of the final script command until you regain control via the mode switch. If you want the aircraft to return home, you can add an RTL (Return to Launch) command to the end of your mission script. If you prefer to land manually and then disarm the motors (which is often preferable to a pre-programmed automatic landing), you must switch to Stabilize mode. Remember, when using RTL, the aircraft returns to the “home” point (the location where it was armed after acquiring a GPS lock). Therefore, when using Auto mode, it is crucial to arm the aircraft at a location where you want it to return—specifically, a spot free of obstacles and away from crowds.

Warning: It is vital to understand that the “home” point is always the actual location where the aircraft was armed!

An RTL or Auto Land command at the end of a mission script will force the aircraft to land and then stop the motors. You cannot manually land the aircraft while in Auto mode unless one of these two options is configured, because the throttle stick controls altitude rather than directly controlling motor speed.

Guided Mode

Guided mode is a feature of APM: Copter that uses a telemetry radio module and a ground station application to guide the aircraft to a target location.

Notice:

Unlike traditional flight modes, there is no dedicated “Guided Mode” setting on the mode switch. To use Guided Mode, you need a telemetry system (such as a 3DR telemetry kit) and a ground station application (like Mission Planner). On the Mission Planner “Flight Data” map screen, simply click on the location where you want the vehicle to fly. Upon reaching the destination, the vehicle will hover and wait for the next target. The “Follow Me” mode is also based on Guided Mode, causing the vehicle to follow you as you move.

What you need to do:

To use Guided Mode, you need a computer or tablet acting as a ground station running software such as Mission Planner, along with a telemetry kit (e.g., 3DR telemetry kit—915MHz for the US or 433MHz for Europe) to enable communication between your computer and the aircraft during flight.

Instructions

After initializing the aircraft, establish a wireless MAVLink connection between the aircraft and the computer.
Check the telemetry module information in the software to ensure the telemetry link is functioning correctly and that a GPS lock has been acquired.
Take off in Stabilize Mode, ascend to a suitable altitude, and then switch to Loiter Mode.
Right-click on the map display in the Mission Planner “Flight Data” tab and select “Fly to Here.”

Enter the desired altitude in the pop-up window. Specify an altitude higher than the “Home” position (in meters).

The map should display the “Guided” destination, and the orange line (navigation heading) should point toward the target location.

Note:

There is no need to set the flight mode to “Guided”.

Acro Stunt Mode

Acro Mode (Rate Mode) uses the remote controller sticks to control the aircraft’s angular velocity. When the sticks are released, the aircraft maintains its current attitude rather than returning to a level position. Acro Mode allows for aerobatic maneuvers—such as flips and rolls—or FPV flying.

Stunt mode is difficult to operate; please do not use it unless necessary. Be mentally prepared for a potential crash before using this mode.

Acro mode is a mode based solely on rate control.

Acro mode provides the most direct control link between the remote controller sticks and the aircraft’s motors.

Flying in Acro mode is like flying an RC helicopter without a flight controller; it requires constant manual stick input.

Overview:

The throttle is fully manual and does not automatically correct the aircraft’s tilt angle. If the pilot moves the throttle stick all the way down, the motors will spin at their minimum speed; however, this behavior can be altered by enabling AirMode.

AC3.1 and later versions include an “Acro Trainer” feature—which can be toggled on or off—designed to make learning aerobatic flight easier.

Throttle stick inputs are interpreted and executed within the “body frame” (as opposed to the “earth frame” used in Stabilize mode). The distinction between the “body frame” and the “earth frame” becomes most apparent when the aircraft is tilted. For example, when tilted 45 degrees forward, applying left yaw with an “earth frame” controller (i.e., Stabilize mode) causes the aircraft to maintain its pitch and roll angles while changing its heading. In contrast, using a “body frame” controller—such as in Acro mode—causes the aircraft to rotate around its own vertical axis, meaning the pitch angle effectively becomes the roll angle, and the roll angle becomes the pitch angle.

Acro is the most difficult flight mode to master; it may take a few crashes before you get the hang of it. Although Acro mode does not strictly require GPS, you may need to switch to RTL in an emergency. Before arming, ensure you have a reliable position estimate—typically provided by a 3D GPS fix with sufficient HDOP.

Detail:

There are two types of Acro mode: the default mode is rate control based on the ground coordinate system (`AXIS_ENABLE = 1`), and the second is rate control based on the aircraft’s body axes (`AXIS_ENABLE = 0`). Flying in this advanced mode is not recommended if the aircraft’s self-leveling capability is poor.

In Acro mode, the angular rates of the aircraft’s Roll, Pitch, and Yaw axes are controlled by the deflection angle of the control sticks.

Centering the sticks maintains the current attitude; alternatively, centering the sticks can be used to return the aircraft to a level attitude.

Moving the pitch and roll sticks causes the aircraft to tilt in the corresponding direction.

To return the aircraft to a level position, the sticks for each axis must be pushed in the opposite direction.

Continuous stick adjustments are required on each axis to maintain level flight.

The default mode utilizes two parameters, expressed as percentages; these are applied to the current roll and pitch angles to determine the angular rate required to return to a level position.

The yaw stick operates in the same manner as it does in stabilized mode.

The throttle stick directly controls the acceleration or deceleration of the four motors based on stick input.

Continuous throttle adjustment is also required to maintain flight altitude.

Flight Mode

Acro mode can be configured to provide full stability at idle throttle. Please refer to AirMode

Stunt training

The ACRO_TRAINER parameter can be set to:

0 = Disabled. This means the pilot operates with full rate control; since there is no auto-leveling, there are no limits on the autopilot’s attitude angles.

1 = Auto-leveling. When the pilot releases the controls, the vehicle will automatically return to a level position. The aggressiveness of this return to level can be controlled using the ACRO_BAL_ROLL and ACRO_BAL_PITCH parameters. The default value of 1.0 results in a return rate of 30 degrees/second; higher values result in a faster return.

2 (Default) = Auto-leveling and tilt angle limiting. This includes the auto-leveling feature of option 1, but additionally prevents the vehicle from tilting beyond 45 degrees (this angle can be configured using the ANGLE_MAX parameter).

A Ch7/Ch8 switch can be used to enable or disable Acro Trainer. With a 3-position switch, the “off” position (PWM < 1200) disables the trainer, the middle position enables option 1 (auto-leveling), and the top position (PWM > 1800) enables option 2 (leveling and tilt angle limiting). A 2-position switch allows selection only between option 0 (disabled) and option 2 (leveling and limiting).

Debug

ACRO_RP_P controls the roll and pitch rotation rate. The default value is 4.5, which commands a rotation rate of 200 degrees per second; higher values increase the rotation speed.
ACRO_YAW_P controls the rotation rate for the yaw axis. The default value of 4.5 (same as for roll and pitch) commands a rotation rate of 200 degrees per second.
ACRO_RP_EXPO and ACRO_Y_EXPO are exponential factors applied to stick inputs specifically in ACRO mode. Since ACRO mode is inherently more responsive than other modes—even near the center stick position—these parameters allow pilots to fine-tune the stick response to better match other modes (such as Stabilize, AltHold, PosHold, etc.). A default value of 0 applies 30% exponential to the pilot’s roll and pitch inputs.

Advanced Adjustment Parameters

Once you have become highly proficient at flying in ACRO mode, you may wish to make more in-depth adjustments based on the drone’s performance characteristics.

These parameters are global parameters applicable to all flight modes, not just ACRO.

ATC_ACCEL_R_MAX and ATC_ACCEL_P:

ATC_ACCEL_R_MAX and ATC_ACCEL_P_MAX: Maximum acceleration on the roll/pitch axes, in degrees/sec². Suppose you have a highly agile quadcopter and your ACRO_RP_P parameter is set to 9, implying a roll rate request of approximately 400 deg/sec. Physically, the copter cannot instantly jump from 0 deg/sec to 400 deg/sec without a brief period of acceleration. During this transition, an error develops within the controller as it works to reach the target rate of 400 deg/sec. When you release the stick, this residual error can cause an overshoot of the desired attitude, followed by a bounce-back. Adjusting this parameter can help eliminate errors during maneuvers and soften the response, potentially mitigating bounce-back. Note that this is entirely different from tuning the “Rate D” term for pitch and roll; this parameter should only be adjusted after those terms have been properly tuned.
ATC_ACCEL_Y_MAX: Maximum acceleration on the yaw axis, in degrees/sec². The principle is the same as for ATC_ACCEL_R_MAX and ATC_ACCEL_P_MAX, but applied to the yaw axis based on the ACRO_YAW_P parameter value (which is typically lower and easier to achieve).

PosHold (Position Hold) Mode

Position mode (formerly known as “Hybrid”) is a new mode introduced in AC3.2. Similar to Loiter mode, it allows the vehicle to maintain a fixed position, heading, and altitude; however, it is often preferred because pilot stick inputs directly control the vehicle’s tilt angle, providing a more “natural” or “fluid” feel.

Overview

When activated, Position Hold mode automatically attempts to maintain the current location, heading, and altitude. Good GPS positioning, low electromagnetic interference affecting the compass, and minimal vibration are all crucial for achieving stable hovering performance.

Control

The pilot can control the aircraft’s horizontal or vertical position using the control sticks.
Horizontal position is adjusted via the Roll and Pitch sticks; the default maximum tilt angle is 45 degrees (this angle can be adjusted using the `ANGLE_MAX` parameter). When the pilot releases the sticks, the aircraft tilts backward to bring the vehicle to a stop.
Altitude is controlled via the throttle stick, similar to Altitude Hold mode.
Heading (yaw) is set using the Yaw stick.
Arming in Loiter mode is possible, but requires a 3D GPS lock and an HDOP of 2.0 or lower.
When a 3D lock is achieved, the blue LED on the APM2 board will remain solid. On the Pixhawk, the LED will turn green (see here for more details on LED modes).
GPS status, satellite count, and positioning accuracy (GPS HDOP) can be clearly viewed in the Mission Planner interface shown below.

The “2/3” values indicate GPS positioning accuracy and the number of satellites (in Position Hold mode, the HDOP must be below 0.8 to unlock/arm).
“4” indicates the GPS status. No GPS: The flight controller does not detect a GPS unit. No Fix: GPS detected, but no satellites found. 3D Fix: More than five GPS satellites acquired.
The maximum braking angle can be set via the PHLD_BRAKE_ANGLE parameter (e.g., 3000 = the vehicle tilts backward by 30 degrees).
The speed at which the vehicle tilts backward to the maximum angle can be set via the PHLD_BRAKE_RATE parameter (e.g., 8 = rotates backward at 8 degrees per second).

Note:

Before using Position Hold mode, ensure high positioning accuracy and the absence of magnetic interference; otherwise, hazardous situations such as drifting, spinning, or loss of control may occur.

Circle Mode

When the vehicle enters Circle mode, it begins circling with a radius of 10 meters, keeping its nose pointed toward the center.

The circle radius can be controlled by adjusting the `CIRCLE_RADIUS` parameter (in meters). Setting `CIRCLE_RADIUS` to zero causes the vehicle to remain in place while slowly rotating (useful for panoramic photography).

The rotation rate (in degrees per second) can be adjusted via the `CIRCLE_RATE` parameter. A positive value indicates clockwise rotation, while a negative value indicates counter-clockwise rotation. If the centripetal acceleration exceeds the limit set by the `WPNAV_ACCEL` parameter (in cm/s/s), the vehicle may not achieve the desired rotation rate.

The pilot cannot control roll or pitch but can adjust altitude using the throttle stick, just as in AltHold or Loiter modes.

The pilot can control the vehicle’s yaw; the autopilot will not regain control of yaw until Circle mode is re-engaged.

During a mission, Circle mode is invoked using the `LOITER_TURNS` mission command.

Drift Mode

Drift mode allows users to fly a multi-rotor aircraft much like an airplane equipped with “automatic coordinated turn” capabilities.

The user directly controls yaw and pitch, while the autopilot manages roll. When using a transmitter with Mode 2 (American-style) configuration, the aircraft can be conveniently controlled using a single stick.

Drift mode is available in APM: Copter firmware version 3.1 or later.

How drift mode works:

When flying a multi-rotor aircraft, use the right stick (on a Mode 2 controller) to control pitch and yaw.
The left stick is primarily used to control altitude; it does not control yaw.
Pushing the right stick forward or backward causes the aircraft to pitch (and accelerate) in the corresponding direction.
Moving the right stick from side to side causes the aircraft to turn in that direction.
The aircraft turns in that direction simultaneously, performing a coordinated turn.
When turning with the right stick, yaw is applied automatically, accompanied by the appropriate amount of roll to counteract velocity along the roll axis.
This allows you to maintain a coordinated (slip-free) turn.
Simply releasing the stick initiates deceleration on the pitch axis, slowing the aircraft down and bringing it to a stop within two seconds.
In Drift Mode, when the right stick is centered, the aircraft maintains its position and hovers (though it may drift slowly in the wind).
Drift Mode relies on GPS for control.
If the GPS signal is lost while flying in Drift Mode, the aircraft will either land or switch to altitude hold, depending on the `failsafe_gps_enabled` setting.
If necessary, be prepared to switch back to Stabilize Mode to regain manual control.

Who is this for:

FPV pilots who want the ability to fly dynamically like an airplane while also being able to hover in a fixed position.
New pilots looking to try a flight mode that is intuitive and easy to learn.
Anyone seeking a flight mode that is simple, easy to master, and fun.
Photography enthusiasts—and videographers in particular—who want smoother, more coordinated footage.

Setting up Drift Mode:

Select “Drift Mode” under the Flight Modes section of the Mission Planner configuration and assign it to a suitable switch.
Further information on tuning Drift Mode is expected soon, along with enhancements being added to the mode.

Simple and Ultra-Simple Modes

Overview

In “Simple” and “Super Simple” modes, the helicopter’s movement can be controlled from the pilot’s perspective, regardless of the direction the helicopter is facing. When the helicopter is far away, making it difficult to adjust roll and pitch inputs based on the aircraft’s orientation, the aircraft’s response remains intuitive.

“Simple” and “Super Simple” modes can be used in conjunction with almost all flight modes, except for “Acro” and “Drift” (where this setting is ignored).

Simple mode allows you to control the helicopter’s movement relative to its own orientation based solely on compass headings.

Super Simple mode allows you to control the helicopter relative to your own position (i.e., the location where it was armed), though this requires a good GPS lock.

Either mode can be assigned to a specific flight mode switch position or enabled/disabled via a Ch7 or Ch8 switch.

When Simple or Super Simple modes are not enabled, the pilot’s stick inputs correspond to the helicopter’s own orientation. For example, in the diagram above, when the pilot applies a correct Roll input (red), the aircraft rolls to the right.

Controlling the aircraft is relatively easy when it is facing the same direction as the pilot; however, when the aircraft is facing the pilot, an inexperienced operator will feel as though the controls are completely reversed—meaning that if the pilot inputs a right Roll, the aircraft moves to the left from the pilot’s perspective.

Simple Mode:

Similar to the “loose” mode found on other systems, this mode allows you to fly the helicopter based on the orientation it had when unlocked, regardless of its current heading.

So, if you push the pitch stick forward, the helicopter moves away from you; pulling the stick back brings it back toward the “home” position. You can even apply yaw in any direction to rotate the helicopter, yet its movement in response to stick inputs will remain the same as it was at takeoff.

Generally, you should stand behind the aircraft when unlocking it, with its nose pointing directly away from you. While flying, try to keep the aircraft in front of your starting position; if it drifts behind you, the controls will effectively be reversed.
As mentioned above, Simple Mode is also very useful in emergencies where the helicopter is far away, and its heading is difficult to determine.

Ultra-Simple Modes:

Super Simple Mode operates similarly to Simple Mode, except that the aircraft’s orientation is referenced to the “Home” position rather than the heading it had when armed. This means that regardless of the aircraft’s location or actual heading, pulling back on the stick will always cause the aircraft to move toward the “Home” position.

The advantage over Simple Mode is that the aircraft can be controlled from the pilot’s perspective even when it is flying behind the pilot or the “Home” position.

If the pilot applies a constant right roll input, the aircraft will fly a clockwise circle around the pilot (though the radius of the circle may increase slightly with each orbit due to “lag”).
A drawback is that this mode requires a GPS lock; therefore, you should ensure a GPS lock is established before takeoff.
When the aircraft is within 10 meters of the “Home” position, the directional reference does not update; consequently, flying in proximity to the “Home” point should be avoided.
To ensure correct control upon takeoff—just as with Simple Mode—the pilot should stand behind the aircraft, facing the same direction as the aircraft’s nose.

Follow-me Mode

It allows the aircraft to act like a “shadowing robot”—wherever you go, it follows you!

The Follow mode is based on the APM: Copter dynamic waypoint function and MAVLink telemetry commands.

The following section describes how to use the “Follow Me” mode on a PC.

You will need:

A multi-rotor aircraft equipped with a data telemetry system

A laptop

A USB GPS receiver

Or a Bluetooth GPS module.

Operating Instructions

Set one of the flight modes to “Loiter.”
In an open area, set up the APM: Copter and establish a wireless connection via MAVLink.
After connecting the USB GPS or Bluetooth device to your laptop, ensure a serial port is detected. Use the software provided with the module to verify that the GPS is functioning correctly and has acquired a satellite lock.
Take off, and once airborne, switch to Loiter mode. (It is advisable to maintain sufficient altitude to ensure the aircraft does not injure you while following.)
On the “Flight Data” screen in Mission Planner, right-click a nearby location and select “Fly to Here.” If this works correctly, you can proceed to try “Follow Me” mode.
Press Ctrl+F in Mission Planner to open the window shown below, then click “Follow Me.”

The window shown above will pop up. Select the serial port assigned to your GPS device; the baud rate does not matter, but you should select the transmission frequency (typically 0.5 Hz).

Once you click “Connect,” Mission Planner will read GPS data from your device and send a “Fly to Here” command to the APM vehicle every two seconds (assuming a 0.5 Hz setting).

Now, pick up your laptop and start walking around.

The vehicle should follow you!

As previously mentioned, maintaining sufficient altitude is essential to avoid injury.

“Follow Me” is a fantastic feature, but please prioritize safety when using it—especially if the propellers are not equipped with protective guards.

Warning:

Like other modes (such as Loiter or AltHold), the vehicle relies on a barometer to measure altitude. This means that over time, the vehicle may drift, and its reported altitude will fluctuate with changes in atmospheric pressure rather than reflecting its actual altitude.

Sport Mode

Also known as “self-leveling mode” combined with altitude hold mode.

Overview

It is designed for FPV or aerial photography flights, as the aircraft maintains the specific angle at which it is set.

The pilot’s roll, pitch, and yaw sticks control the vehicle’s rotation rate; when the sticks are released, the aircraft maintains its current attitude.

The vehicle will not tilt beyond 45 degrees (this angle is adjustable via the `ANGLE_MAX` parameter).

Altitude hold is managed by an altitude controller, so the aircraft attempts to maintain its current altitude when the throttle stick is positioned within the center 10% of its range. It will climb or descend at speeds of up to 2.5 m/s (this speed is adjustable via the `PILOT_VELZ_MAX` parameter).

Auto-Tune Mode

Overview

Auto-tune attempts to automatically adjust Stabilize P, Rate P and D, as well as maximum rotational acceleration, to provide the highest responsiveness without significant overshoot. Before using Auto-tune mode, the vehicle should be flown “basically” in AltHold mode, as the function requires the ability to “twitch” the vehicle along the roll and pitch axes.

Pre-flight Setup

1. Set the flight mode switch to AltHold.

Note: Firmware version AC3.5 and later supports switching directly to AutoTune from Loiter mode.

2. Assign the AutoTune function to an auxiliary switch to enable or disable AutoTune using that switch.

3. Remove the camera gimbal or any other frame components that might oscillate during flight.

4. Use the AUTOTUNE_AXES parameter to select the combination of axes (Roll, Pitch, Yaw) to be tuned.

5. Set the auto-tune responsiveness using the AUTOTUNE_AGGR parameter (0.1 = aggressive, 0.075 = normal, 0.050 = mild); typically, start with the default value of 0.1.

6. For large copters (at least 13 inches or 33 cm in diameter), set the Roll and Pitch rate filters to 10 Hz (parameters are RATE_RLL_FILT_HZ and RATE_PIT_FILT_HZ in Copter-3.3, and ATC_RAT_RLL_FILT and ATC_RAT_PIT_FILT in Copter-3.4).

7. It is recommended to enable battery voltage scaling for PID gains.

How to Initiate Auto-Tune

1. Choose a day with good weather and go to an open area.

2. Ensure the CH7 or CH8 switch is in the low position.

3. Take off to a suitable altitude and set the helicopter to Altitude Hold mode.

4. Orient the aircraft so that it is positioned 90 degrees relative to the wind direction (i.e., first adjust the Roll to point the aircraft into the wind).

5. Set the ch7/ch8 switch to the HIGH position to initiate AutoTune:

You will see the copter oscillate left and right by approximately 20 degrees for a few minutes, followed by repeated forward and backward movements.

You can use Roll and Pitch inputs to reposition the copter at any time if it drifts (it will use the original PID gains during repositioning and testing). When you release the sticks, it will resume AutoTuning from the new position.

Switch the ch7/ch8 switch to the LOW position at any time to stop AutoTune and revert to the original PID gains.

Ensure there is no trim applied on your transmitter; otherwise, AutoTune may fail to detect the stick-centered signal.

6. Once tuning is complete, the copter will revert to the original PID gains.

7. Toggle the ch7/ch8 switch from LOW to HIGH to test the tuned PID gains.

8. Set the ch7/ch8 switch to the LOW position to fly using the original PID gains.

9. If you are satisfied with the AutoTuned PID gains, set the ch7/ch8 switch to the HIGH position, then land and disarm to permanently save the PIDs.

If you are not satisfied with the new PIDs, switch ch7/ch8 to LOW to revert to the original PIDs; the results will not be saved upon disarming.

If you notice excessive twitching in Stabilize, AltHold, or Loiter modes after AutoTuning (but not in more autonomous modes like PosHold, RTL, or Auto), try reducing the RC_FEEL parameter to 0.25. Alternatively, try reducing the AUTOTUNE_AGGR parameter (which should generally be between 0.05 and 0.10) and run the process again.

If the copter feels sluggish after AutoTuning, try increasing the AUTOTUNE_AGGR parameter to 0.10 and run AutoTune again.

Invoke auto-tuning mode using fixed-point mode.

In Copter-3.5 (and later versions), if AutoTune mode is initiated from a hover or position-hold flight mode (as opposed to altitude-hold), position holding will be relatively weak.

The vehicle will gently tilt (up to 10 degrees) toward the “target point” (initially set to the vehicle’s starting location), at which point the AutoTune mode is engaged.

The pilot can use the Roll, Pitch, Yaw, or throttle sticks to reposition the vehicle. The target location will reset to the vehicle’s current position whenever the pilot releases the Roll and Pitch sticks.

To test response perpendicular to the wind, the vehicle may suddenly rotate 90 degrees in any direction if it drifts 5 meters (or more) away from the target location.

In light or no-wind conditions, making minor position adjustments might cause the vehicle to oscillate back and forth; it may change its yaw orientation around the target point each time it drifts more than 5 meters away. In such cases, reverting to a simpler AltHold-based AutoTune might be more comfortable.

Additional Information

In Copter-3.3 (and later versions), AutoTune can be set as a flight mode. Entering or exiting the AutoTune flight mode produces the same response as toggling the Ch7/Ch8 auxiliary switch assigned to the AutoTune function.
The `AUTOTUNE_AXES` parameter is useful when the battery lacks sufficient capacity to tune all axes, as it lets you select which axes to tune. “1” = tune Roll, “2” = tune Pitch, “4” = tune Yaw. Add these numbers together to tune multiple axes in a single session (e.g., “7” = tune all axes).
`AUTOTUNE_AGGR`: Should be in the range of 0.05 to 0.10. Higher values result in more aggressive tuning but can sometimes lead to excessively high gains. More specifically, this parameter controls the thresholds for D-term bounce-back and P-term overshoot. This affects tuning noise immunity (higher values better handle frame flex or other disturbances that might trigger the tuning algorithm). However, higher values also affect the system’s ability to reject external disturbances, while lower values make tuning more sensitive to pilot inputs.

Complete list of parameters that may be updated by Auto-Tune:

Roll angle P gain: ATC_ANG_RLL_P (in AC3.3: STB_RLL_P)
Roll rate P, I, and D gains: ATC_RAT_RLL_P, ATC_RAT_RLL_I, ATC_RAT_RLL_D (in AC3.3: RATE_RLL_P, RATE_RLL_I, RATE_RLL_D)
Roll maximum acceleration: ATC_ACCEL_R_MAX
Pitch angle P gain: ATC_ANG_PIT_P (in AC3.3: STB_PIT_P)
Pitch rate P, I, and D gains: ATC_RAT_PIT_P, ATC_RAT_PIT_I, ATC_RAT_PIT_D (in AC3.3: RATE_PIT_P, RATE_PIT_I, RATE_PIT_D)
Pitch maximum acceleration: ATC_ACCEL_P_MAX
Yaw angle P gain: ATC_ANG_YAW_P (in AC3.3: STB_YAW_P)
Yaw rate P, I, and D gains: ATC_RAT_YAW_P, ATC_RAT_YAW_I, ATC_RAT_YAW_D (in AC3.3: RATE_YAW_P, RATE_YAW_I, RATE_YAW_D)
Yaw rate filter: ATC_RAT_YAW_FILT (in AC3.3: RATE_YAW_FILT_HZ)
Yaw maximum acceleration: ATC_ACCEL_Y_MAX
Roll and Pitch axis rate feed-forward enabled (ATC_RATE_FF_ENABLE)
After tuning, you may wish to increase ATC_THR_MIX_MAX (or MOT_THR_MIX_MAX in AC3.3) to 0.9 (default is 0.5) to prioritize attitude control over throttle control. If the aircraft decelerates suddenly after rapid forward flight, this can reduce the excessive pitch values sometimes observed in Altitude Hold mode (especially with helicopters using large propellers). In this scenario, wind gets trapped beneath the lift-generating propellers, disrupting the aircraft’s attitude and creating a conflict between throttle and attitude control. The risk of increasing this parameter value is that if the rate gain becomes too high—causing significant vibration—the aircraft may struggle to descend (as it prioritizes correcting attitude oscillations over sufficiently reducing throttle).
Auto-tuning can command large, rapid output changes to the motors, which may lead to motor synchronization issues, particularly when using SimonK firmware or low-KV motors (below 500KV).
Auto-tuning sometimes fails to find suitable settings for flight controllers or arms with very soft vibration damping.
For best results, the aircraft should not build up excessive horizontal speed. You can prevent the vehicle from flying too fast by making quick corrections between the test movements (twitches).
It is recommended to perform auto-tuning starting from Stabilize mode; do not abruptly flip the auto-tune switch before switching to Altitude Hold mode.

Frequently Asked Questions

If the vehicle is in AutoTune mode but does not begin tuning (i.e., it does not oscillate), the most likely reason is that the Roll, Pitch, Yaw, or throttle sticks are not perfectly centered. Increasing the RC input deadzone by setting RC1_DZ, RC2_DZ, RC3_DZ, and RC4_DZ to 50 (or higher) may help.
If AutoTune causes the vehicle to twitch excessively, try reducing the AUTOTUNE_AGGR parameter (do not go below 0.05) and run AutoTune again.
If AutoTune makes the vehicle sluggish, try increasing the AUTOTUNE_AGGR parameter (do not exceed 0.1) and run AutoTune again.

Landing Mode

The Land mode allows the vehicle to descend vertically and features the following characteristics:

During the descent to 10 meters (or until the sonar detects an object beneath the vehicle), the standard altitude hold controller is used, and the descent speed is limited by the `WPNAV_SPEED_DN` parameter; this parameter can be modified in Mission Planner under the **Config/Tuning** > **ArduCopter Pids** (Extended Tuning) tab.

Within a range of 10 meters, the aircraft descends at the rate specified by the LAND_SPEED parameter, which defaults to 50 cm/s.

Upon landing, if the pilot’s throttle is at the lowest position, the aircraft will automatically shut down the motors and lock the system.

Note: If the motor speed is at the minimum and the climb rate is between -20 cm/s and +20 cm/s, APM: Copter will detect a landing after one second. It does not use altitude to determine whether to shut off the motors, unless the aircraft is more than 10 meters below the home altitude.

If the aircraft jumps up or rises like a balloon before landing or shutting down the propellers, try slightly lowering the `LAND_SPEED` parameter.
If the model has a GPS lock, the landing controller will attempt to maintain its horizontal position, though the pilot can still adjust the target horizontal position, just as in Loiter mode.
If the model does not have a GPS lock, horizontal control operates similarly to Stabilize mode, but the pilot retains control over the aircraft’s roll and pitch angles.

Warning!

When operating in any altitude-hold mode—including Altitude Hold, Loiter, Auto, Auto-Land, or Return to Launch (RTL)—if the aircraft becomes unstable as it approaches the ground or lands (e.g., erratic vertical movement during auto-landing or failure to shut down motors correctly after landing), this may be due to pressure fluctuations caused by the interaction between the propeller wash and the ground. These fluctuations can interfere with the flight controller’s barometer (altimeter).

This issue is easily identified by examining the altimeter readings in the flight logs for spikes or oscillations as the aircraft nears the ground.
If this problem occurs, relocate the flight controller away from the area affected by propeller wash or enclose it in a ventilated housing.
Success can be verified through flight testing or by analyzing the flight logs.