> For the complete documentation index, see [llms.txt](https://docs.auterion.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.auterion.com/vehicle-operation/dragon-setup/dragon-mr-lr/catapult-launch.md).

# Catapult launch

The launch detector is enabled and tuned with the `FW_LAUN_*` parameters. It uses the vehicle's acceleration to trigger a launch. 

| Parameter          | Default   | Unit | Meaning                                                                                                     |
| ------------------ | --------- | ---- | ----------------------------------------------------------------------------------------------------------- |
| `FW_LAUN_DETCN_ON` | `0` (off) | bool | Master enable. **Set to 1 for catapult/hand launch.** Not compatible with runway takeoff.                   |
| `FW_LAUN_AC_THLD`  | `30.0`    | m/s² | Acceleration norm that must be exceeded to call it a launch.                                                |
| `FW_LAUN_AC_T`     | `0.05`    | s    | How long acceleration must stay above the threshold before launch is declared.                              |
| `FW_LAUN_MOT_DEL`  | `0.0`     | s    | Delay from launch detection until full throttle. `0` = motor enabled immediately on detection.              |
| `FW_LAUN_CS_LK_DY` | `0.0`     | s    | Locks the selected control surfaces while armed and until this time after launch. `0` = no surface locking. |

How it behaves: while armed and waiting, throttle is held down. When acceleration exceeds `FW_LAUN_AC_THLD` for `FW_LAUN_AC_T` seconds, launch is detected. If `FW_LAUN_MOT_DEL > 0` the aircraft controls attitude at idle throttle for that delay (useful to clear the catapult before thrust), then goes to full throttle; otherwise the motor is enabled immediately.

### Launch procedure

#### Preparation

1. Power up the vehicle in Position mode.
2. Complete the pre-flight checklist in the treeline. This includes a control surface check (using manual mode, keyboard control, or the actuator tab) to confirm that the motor spins and turns in the correct direction.
3. Assemble the catapult.
4. Place the vehicle onto the catapult without powering it off.

#### Takeoff

The launch can be performed either as a mission takeoff or as a manual takeoff.

**Mission takeoff**

1. Plan a mission that includes a takeoff.
2. Upload the mission to the vehicle.
3. Arm the vehicle.
4. Start the mission.
5. Trigger the catapult. The motor starts spinning automatically at full throttle once launch is detected.

**Manual takeoff**

1. Arm the vehicle.
2. Throttle up.
3. Trigger the catapult.

#### Before launch

Remove the safety pin from the payload, then launch.

Upon placing the vehicle on the catapult, you might see the heading changing to a wrong value. This must be compensated by a manual heading reset. Compass calibrations should only ever be performed with the vehicle away from any metallic objects. Make sure to use a compass to determine the vehicle's real heading and set the heading in AMC accordingly before launch.

If performing a tube launch, the control surfaces need to be locked. To achieve this, use `FW_LAUN_CS_LK_DY`

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