RTH Fail-safes Explained (and how to test safely)

Introduction

Return-to-Home (RTH) is your drone's emergency autopilot. When things go wrong—signal loss, low battery, or pilot panic—RTH is supposed to save your drone by flying it back to you. But RTH is not foolproof. Incorrect settings, GPS errors, or obstacles can turn RTH into a disaster.

This guide explains how RTH works, the different types of RTH, how to configure it correctly, and how to test it safely before you need it. Don't skip the testing step—it's the difference between a successful recovery and a lost drone. For official safety guidelines, see FAA UAS Resources. Explore our Pre-Flight Checklist or visit the Compare tool for RTH-capable drones.

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1. How RTH Works

When RTH is triggered, the drone follows this sequence:

1. Ascends to the preset RTH altitude (if current altitude is lower)
2. Flies in a straight line back to the home point (GPS coordinates)
3. Descends and attempts to land at the home point
4. Lands (some drones use Precision Landing with downward cameras)

Home Point: The Starting Location

The home point is the GPS location recorded when:

• The drone achieves GPS lock after power-on (automatic)
• You manually update home point in the app

Common mistake: Taking off before GPS lock. The drone may use a cached location (from a previous flight, possibly miles away) as home point. Always verify home point on the map before takeoff.

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2. Types of RTH

Most drones have three types of RTH, each triggered by different conditions:

A) Low Battery RTH

Trigger: Battery voltage drops below a preset threshold (typically 30–15%).

Behavior:

1. Drone displays "Low Battery, Returning to Home" warning
2. Ascends to RTH altitude (if needed)
3. Flies back to home point
4. Lands automatically

Can you cancel? Yes, within the first 10 seconds (varies by model). After that, RTH is forced.

Risk: If you're flying far away and battery is critically low, the drone may not have enough power to return—it will auto-land wherever it is (potentially in water, traffic, or trees).

B) Lost Signal RTH (Failsafe RTH)

Trigger: Controller loses connection with the drone for >3–6 seconds (varies by model).

Behavior:

1. Drone hovers for a few seconds (waiting for signal)
2. If signal doesn't return, triggers RTH
3. Ascends to RTH altitude, flies back, lands

Can you cancel? Yes, once signal is reestablished, you regain control (but RTH may continue unless you actively cancel).

Risk: Signal loss can be caused by:

• Flying too far (beyond range)
• Obstacles blocking signal (buildings, hills)
• Interference (Wi-Fi, power lines, other drones)

C) Manual RTH (Smart RTH)

Trigger: You press the RTH button on the controller or in the app.

Behavior:

• Same as other RTH types: ascend, fly back, land
• You can cancel anytime by pressing RTH button again or moving the joysticks

Use cases:

• You're lost or disoriented (can't see the drone, don't know which way is home)
• Emergency (e.g., people walking into the area, unexpected hazard)
• Testing RTH functionality

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3. Configuring RTH: Altitude and Home Point

RTH Altitude (Critical!)

What it is: The height the drone climbs to before flying back.

Why it matters: If RTH altitude is too low, the drone will hit obstacles (trees, buildings, power lines) during the return flight.

How to set it:

1. Open your drone app (e.g., DJI Fly, Autel Sky)
2. Go to Settings → Safety → RTH Altitude
3. Set it to at least 20–30m higher than the tallest obstacle within 500m of your home point

Examples:

• Open field: 50m is safe
• Suburban area with houses: 80–100m
• Near tall buildings/trees: 120m (max allowed in many regions)

Home Point Update

When to update:

• You move your takeoff location (e.g., landing pad on a moving vehicle)
• GPS lock was weak at takeoff, and you want to refresh it

How to update:

1. Hover the drone at current location
2. Open app → Safety → Update Home Point
3. Choose "Current Aircraft Location" or "Current Controller Location"

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4. How to Test RTH Safely

Never assume RTH works. Test it before every new location (or at least once per drone if you're confident in its reliability).

Test RTH: Step-by-Step

1. Choose a safe location:

   • Wide-open area (field, park, empty lot)
   • No obstacles within 100m (no trees, buildings, power lines)
   • No people, animals, or vehicles nearby

2. Verify home point:

   • Check the map in your app—home point marker should be at your feet

3. Take off to 5–10m altitude:

   • Hover and stabilize

4. Fly 20–30m away:

   • Keep drone in sight, fly slowly

5. Trigger RTH:

   • Press RTH button on controller or app
   • Watch the drone's behavior:
     • It should ascend to RTH altitude (if set higher than current altitude)
     • It should fly back in a straight line toward you
     • It should descend and land near the takeoff point

6. Cancel RTH (optional):

   • Once you confirm it's working, you can cancel RTH and land manually
   • Or let it complete the full sequence

7. Repeat in different scenarios (optional):

   • Test with higher altitude (50m+)
   • Test with longer distance (100m+)
   • Test Lost Signal RTH (turn off controller briefly—only if confident!)

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5. Common Mistakes and How to Avoid Them

Mistake #1: RTH Altitude Too Low

Problem: RTH altitude is 30m, but there's a 40m tree between you and the drone.
Result: Drone flies into tree during RTH.
Fix: Always set RTH altitude higher than the tallest obstacle within 500m.

Mistake #2: Wrong Home Point

Problem: You took off before GPS lock. Home point is cached from last flight (2 km away).
Result: RTH flies the drone to the wrong location (often into traffic, buildings, or out of sight).
Fix: Always wait for GPS lock before takeoff. Verify home point on map.

Mistake #3: Ignoring Low Battery Warning

Problem: Battery hits 20%, you keep flying. Forced RTH triggers at 15%, but drone doesn't have enough power to return.
Result: Drone auto-lands in water, trees, or a road.
Fix: Return manually as soon as you see 30% battery. Don't wait for forced RTH.

Mistake #4: Not Testing RTH

Problem: You fly 500m away, lose signal, assume RTH will work—but it doesn't (wrong home point, obstacle in path, etc.).
Result: Lost drone.
Fix: Test RTH in a safe area before flying far or high.

Mistake #5: Relying on RTH in Wind

Problem: Strong wind. Drone triggers RTH, but wind pushes it sideways—it drifts into a building or out of range.
Result: Crash or flyaway.
Fix: In strong wind, fly manually back. Don't rely on RTH—it flies in a straight line and doesn't account for wind drift.

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6. Advanced RTH Features

Some drones have enhanced RTH capabilities:

Precision Landing

What it is: The drone takes a photo of the ground at takeoff. During RTH, it matches the image to land precisely at the same spot.

Pros: Accurate landing (within 1–2m)
Cons: Only works in good light and textured surfaces (not featureless grass or water)

Obstacle Avoidance During RTH

What it is: Forward/upward sensors detect obstacles and automatically avoid them during RTH.

Pros: Safer—less likely to hit trees or buildings
Cons: Sensors may not work in low light, heavy rain, or with thin obstacles (wires, branches)

Dynamic RTH Altitude

What it is: The drone records its flight path and uses that path (instead of a straight line) to return home.

Pros: Avoids obstacles it flew around on the way out
Cons: Uses more battery, only available on high-end drones (DJI Mavic 3, Autel EVO II)

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7. Scenarios: What to Do When…

Scenario A: Lost Signal

1. Don't panic. Drone will hover or RTH automatically.
2. Move to higher ground or away from obstacles.
3. Wait 10–20 seconds for signal to reconnect.
4. If signal returns, cancel RTH and fly manually back.
5. If signal doesn't return, let RTH complete—the drone will come back to home point.

Scenario B: Low Battery

1. Start returning immediately (don't wait for forced RTH).
2. Fly direct route at medium speed (not full speed—wastes battery).
3. If forced RTH triggers, let it continue (canceling wastes time).
4. If drone auto-lands mid-flight, note the location and retrieve it ASAP.

Scenario C: Wind Too Strong

1. Fly back manually—don't rely on RTH (it flies in a straight line, ignoring wind drift).
2. Fly low (wind is stronger at higher altitudes).
3. If battery is low, land safely in the nearest safe spot (field, parking lot)—don't force it to return home.

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Conclusion

RTH is a lifesaver—when configured correctly. But it's not magic. Wrong home point, low RTH altitude, or strong wind can turn RTH into a disaster. The solution is simple:

1. Verify home point before every flight
2. Set RTH altitude higher than all obstacles
3. Test RTH in a safe area
4. Fly conservatively—return manually at 30% battery, don't wait for forced RTH

Master these basics, and you'll never lose a drone to a preventable RTH failure.

Next steps: Review our Pre-Flight Checklist, understand Weather Limits, and maintain Battery Health. Ready to compare drones? Visit our Compare tool.

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Frequently Asked Questions

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Continue reading → Pre-Flight Checklist · Weather & Drones · Battery Health

Last updated: 2025-10-12