Guided Course Mode (Fixed-Wing)

Guided Course mode maintains a constant ground track (course), altitude, and airspeed without any manual stick input. The operator controls the vehicle entirely via GCS commands, making it the guided equivalent of Position mode.

TIP

This mode is suited to situations where an operator wants to guide a fixed-wing vehicle from a GCS without manual control.

INFO

• Requires a horizontal velocity estimate (e.g. GPS/dead-reckoning). Course commands will be rejected if the velocity estimate is unavailable.
• Manual control input is ignored.

Overview

On activation, the vehicle captures its current velocity over ground vector as the initial course bearing and holds altitude and airspeed from the moment of activation. The vehicle then flies that course indefinitely until the operator issues a new command.

There is no waypoint sequencing or autonomous path planning: the GCS guides the vehicle in real time by sending individual commands.

Supported Commands

The following commands are accepted while in Guided Course mode:

Command	Effect
MAV_CMD_GUIDED_CHANGE_HEADING	Set a new course bearing (degrees, 0 = north) with HEADING_TYPE = 0. Rejected if horizontal velocity estimate is unavailable.
MAV_CMD_DO_CHANGE_ALTITUDE	Set a new target altitude (AMSL, metres).
MAV_CMD_DO_CHANGE_SPEED	Set a new equivalent airspeed via param2 (m/s). If param2 ≤ 0, the default cruise speed is restored.

Technical Description

The navigator mode (course.cpp) sets a position setpoint with course (ground track bearing) and alt fields populated, and yaw = NAN.

The fixed-wing mode manager (FixedWingModeManager) detects the finite course field and bypasses normal waypoint sequencing, calling navigateBearing() from the directional guidance library to compute lateral acceleration and course setpoints. Longitudinal control targets the altitude and airspeed from the setpoint.

Failsafe Behaviour

Guided Course is classified as an AUTO mode for failsafe purposes. The following failsafe exception parameters apply:

Parameter	Bit	Effect when set
COM_RCL_EXCEPT	1 (Auto modes)	RC loss does not trigger a failsafe in this mode.
COM_DLL_EXCEPT	1 (Auto modes)	GCS connection loss does not trigger a failsafe.

WARNING

Since Guided Course is driven entirely by GCS commands, operators should carefully consider the datalink loss failsafe setting (COM_DLL_EXCEPT bit 1). If the GCS link drops, the vehicle will continue on its last commanded course indefinitely. It is strongly recommended to either leave the datalink failsafe active or ensure a secondary safety mechanism (e.g. geofence, battery failsafe) is in place.

Parameters

Parameter	Description
FW_AIRSPD_TRIM	Default cruise airspeed used on activation and when MAV_CMD_DO_CHANGE_SPEED is sent with value ≤ 0.
FW_AIRSPD_MIN	Minimum airspeed. Commanded airspeed is clamped to this value.
FW_AIRSPD_MAX	Maximum airspeed. Commanded airspeed is clamped to this value.
COM_RCL_EXCEPT	RC loss failsafe exceptions bitmask. Bit 1 covers all auto modes including Guided Course.
COM_DLL_EXCEPT	Datalink loss failsafe exceptions bitmask. Bit 1 covers all auto modes including Guided Course.