How Return to Home (RTH) or Return to Launch (RTL) works
Return to Home (RTH), also commonly referred to as Return to Launch (RTL), is one of the most important safety features of our autopilot systems. This safeguard is designed to get the aircraft back to you in the event of an emergency or potential emergency.
> some features vary by autopilot; this guide focuses on the Agriculture E6 Autopilot system.
> see your Ground Station Application settings to determine exact RTL height and low battery voltages.
> The pilot in command is ultimately responsible for the safety and operation of the aircraft.
> In cases of a critical low-battery emergency, the autopilot is not accounting for distance to the home point; always observe your battery level and do not rely solely on this feature
Let's first start with WHEN and HOW the RTH feature is activated:
By the default setting, RTH will activate in any of the following situations
- Critical Low Battery: at the second-level low-battery alarm (also called 'critical low battery'; see your battery alert settings on your Ground Control Station software - GCS)
- Lost Communications: If the UAV loses connection to the Remote Controller (RC), the aircraft will stop it's activity*
- User Activated: there is a switch on your RC and a button on your GCS app where you can manually activate the RTH
- Pre-Programmed in Flight Plan: you can add RTH as a command during your plan. For example, the E6 agriculture spraying autopilot can be set to automatically RTH when the spray tank is emptied. Or you could add the command at the end of a mapping mission or inspection flight.
Let's now look at WHAT happens when RTH is activated:
Regardless of the reason the RTH is activated, the aircraft will take these steps in the order listed below:
- Interrupts the current flight plan and hovers in place (regardless whether being flown by the RC or on an automatic flight plan*)
- The UAV climbs to the predetermined default height (usually 30M, see GCS settings)
- Once at height, the drone flies in a direct path straight back to the place where you armed the motors or launched the aircraft on that flight. Note: some GCS have the option to set a new 'home' point during the flight. If you did this, the aircraft will return to the new established home.
- Once above the home position, the aircraft will slowly descend to the ground; during this final stage, the operator can move the aircraft from side-to-side allowing you to fine-tune the landing place, avoid an uneven landing spot, etc.
- Once all the way on the ground, the aircraft will stop the propellers and disarm.
* this feature may be deactivated on long-range fixed-wing drones which use the GCS for communications - in this case, your GCS might be setup to allow losing RC communications but must maintain the GCS link - or it can be setup to allow both to disconnect as the flight plan is saved on board the aircraft. Discuss this with your Sales Associate or Training Instructor.
How do you interrupt or cancel RTH mode?
At any time during the RTH, you can interrupt the program by switching the flight mode on the RC to Manual Mode (also known as Loiter, Att/Attitude mode) and then quickly back to Autohover Mode (also known as GPS or whatever allows you to hover in place and fly by RC).
Note: critical low battery situations will not allow you to interrupt the RTL process!
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