Vertical take-off and landing flight

Although flying QuadPlane is actually easier than traditional fixed-wing aircraft, there are still some things to understand. Please read the following sections carefully.

Transition

The QuadPlane transition is where the aircraft transitions between being primarily a vertical take-off and landing vehicle (VTOL) flight and being a traditional fixed-wing aircraft flight. The transition takes place in two directions, either by the pilot or by switching between airspeed and flight mode.

The main method to start the transition is to change the flight mode, either using the flight mode channel on the remote control or using the ground station command mode to change.

If you switch to manual, the rotor motor will stop immediately.
If you switch to any other fixed-wing mode, the rotor motor will continue to provide lift and stability until you reach the ARSPD_FBW_MIN airspeed (if no airspeed sensor is available, the airspeed estimate).
If you switch to any other fixed-wing mode, the rotor motor will continue to provide lift and stability until you reach the ARSPD_FBW_MIN airspeed (if no airspeed sensor is available, the airspeed estimate).
If you switch from fixed wing mode to QuadPlane mode, the forward motor will stop immediately, but the control plane will continue to provide stability while the aircraft is decelerating. This allows switching to QuadPlane mode at high speeds.
If the Q_VFWD_GAIN parameter is set to a non-zero value, there is an exception to the positive motor stop in QuadPlane VTOL mode. In this case, the forward motor will be used to maintain the height of the aircraft in the wind. See the description of Q_VFWD_GAIN.

Auxiliary fixed-wing flight

The QuadPlane code can also be configured to assist the fixed wing in any flight mode other than MANUAL. To enable rotor motor assistance, you should set the Q_ASSIST_SPEED parameter to the airspeed you need to help.

When Q_ASSIST_SPEED is non-zero, the rotor motor will assist stability and boost each time airspeed falls below this threshold. For example, this can be used to allow flying at very low speeds in FBWA mode, or for auxiliary automatic fixed wing takeoffs

From version 3.7.0, additional auxiliary types can be provided based on gesture errors. If Q_ASSIST_ANGLE is non-zero, then this parameter will give an attitude error even if the airspeed is higher than Q_ASSIST_SPEED, above which an assist will be enabled. Pose assist is only used when Q_ASSIST_SPEED is greater than zero.

The assistance provided by the rotor motor depends on the fixed wing flight mode. If you are flying in autonomous or semi-autonomous mode, the rotor motor will attempt to assist in the required climb rate and cornering speed of the autonomous flight mode when assist is enabled (ie airspeed is lower than Q_ASSIST_SPEED or attitude error is higher than Q_ASSIST_ANGLE). In semi-manual mode, the Quartet will try to provide help for the input of the flight crew.

The specific processing is:

In automatic mode, the rotor motor will provide lift to the next waypoint altitude and will help turn the airplane at the speed required by the navigation controller.
In automatic mode, the rotor motor will provide lift to the next waypoint altitude and will help turn the airplane at the speed required by the navigation controller.
In CRUISE or FBWB mode, the rotor motor will provide lift based on the pilot's required climb speed (controlled by the pitch lever). The rotor motor will try to turn to the pilot's required turning speed (combined with aileron and rudder inputs).
In FBWA mode, the rotor motor will assume that the lifter input is proportional to the user's desired climb rate. Therefore, if the user pulls back the push rod, the rotor motor will try to climb, and if the user pushes forward, the rotor motor will try to provide a stable drop.
In AUTOTUNE mode, quad will provide the same help as FBWA, but using AUTOTUNE mode with high Q_ASSIST_SPEED value is not a good idea because the rotor motor assist will interfere with the learning of the fixed wing gain.

In MANUAL, ACRO and TRAINING modes, the rotor motor will be fully closed. In these modes, the aircraft will fly purely as a fixed wing.

In STABILIZE mode, if the auxiliary function is turned on, the rotor motor will attempt to provide lift.

Return flight

When flying QuadPlane, you can choose several ways to handle the return to startup. The choice is:

As a fixed wing, around the return point

As a vertical take-off, landing vertically to the return point

Fly as a fixed-wing aircraft until close to the return point, then switch to vertical landing gear and vertical landing

In each case, a key concept is the return point. This is defined as the nearest return point, or if no return point is defined, the home position.

RTL Fixed wing RTL

The default behavior of the RTL mode is the same as for the fixed wing. It will fly to the nearest meeting point (if you do not define a rendezvous point, go home) and fly around this point. Unless the aircraft is below the airspeed defined in Q_ASSIST_SPEED, no vertical take-off motor will be used. The height at which the aircraft will take off will be the height of the rendezvous point, or ALT_HOLD_RTL if no rendezvous point is used.

VTOL RTL（QRTL）

Mixed RTL

In QuadPlane, the last option for RTL was to fly as a fixed-wing aircraft until it reached the return point, and then switch to the VTOL RTL described above. To enable this type of hybrid RTL mode, you need to set the Q_RTL_MODE parameter to 1.

The initial height to be reached in the fixed wing portion of the hybrid RTL is the same as the initial height for the fixed wing RTL. You should set your rendezvous height and ALT_HOLD_RTL options appropriately to ensure that the aircraft reaches a reasonable height for a vertical landing. A landing altitude of about 15 meters is good for many QuadPlanes. This should be greater than or equal to the Q_RTL_ALT value.

The distance from the airplane to the point of return from the fixed wing to the vertical take-off and landing flight is set using the RTL_RADIUS parameter. If not set, the WP_LOITER_RAD parameter is used. The aircraft decelerates as it approaches the home point. The target is the altitude set by Q_RTL_ALT.

Once the return point is reached, the aircraft begins to descend and land, as described in the VTOL RTL model above.

What will happen?

Understanding hybrid aircraft may be difficult at first, so here are some scenarios and how the ArduPilot code handles them.

Hover in QHOVER and switch to FBWA mode

The aircraft will continue to circle and wait for the pilot to input. If you take the handle from the rocker when you are at zero throttle, the airplane will continue to maintain its current altitude and maintain its own level. It will drift in the wind because it does not hold position.

If the throttle lever is pushed up, the throttle motor will speed up and the airplane will begin to move forward. As the aircraft moves slowly, the rotor motor will continue to provide lift and stability. You can control the attitude of the airplane by scrolling and direction input. When you use a pitch (elevator) that affects the climb rate of a rotor motor. If you pull down the throttle, a four-wheel motor will assist the aircraft in climbing. If you push on the putter, the power of the rotor motor will decrease and the airplane will fall.

The roll and pitch inputs also control the attitude of the aircraft, so a low speed right hand will move the aircraft to the right. This will also cause the airplane to yaw to the right (because the QuadPlane code interprets the right aileron in fixed-wing mode as a commanded turn).

Once the aircraft's airspeed reaches ALSPD_FBW_MIN (or Q_ASSIST_SPEED, if it is set and greater than ALSPPD_FBW_MIN), the auxiliary amount provided by the rotor motor will continue to decrease within 5s. After that, the aircraft will fly as a fixed wing

I fly fast in FBWA mode and switch to QHOVER mode

Four-wheel motors will immediately participate and will begin to hold aircraft at the current height. The climb/fall speed is now set by the throttle lever. The higher the throttle lever is, the lower the throttle lever is. In the middle, insist that the aircraft will maintain altitude.

The forward motor will stop, but due to its power, the aircraft will continue to move forward. The resistance of the air will slowly stop. The aircraft's attitude can be controlled by roll and pitch joysticks (ailerons and elevators). You can use the rudder to fly the plane.

Switch to RTL mode when hovering

The aircraft will transition to fixed-wing flight. The four motors will provide assistance with the elevator and attitude, while the forward motor will start to pull the aircraft forward.

A normal aircraft RTL flight plan will then be run, which defaults to hovering above the RTL altitude above the arming position or the nearest pull point. If you have the RTL_AUTOLAND setting, the airplane will have a fixed wing landing.

If Q_RTL_MODE is set to 1, the aircraft will switch to VTOL landing near the return point.

Flight