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Betaflight GPS Rescue

Summary

GPS Rescue is Betaflight's automatic return-to-home failsafe. When the RC link is lost for longer than the configured timeout, the FC switches to GPS-guided navigation: it climbs to a safe altitude, heads toward the arm point, and descends when it arrives. GPS Rescue requires a GPS fix of at least 8 satellites acquired before arming. The home point is recorded at arm time — if the pilot moves after arming, GPS Rescue returns the drone to where the pilot was standing when they armed. All parameters in the base configuration are conservative defaults; the return altitude must be adjusted for local terrain and obstacles before each deployment.

Concept

What GPS Rescue does

When RC link loss is detected for longer than failsafe_delay (default 1s), Betaflight transitions through its failsafe stages:

  1. Stage 1 (link loss detected): holds last known stick positions briefly
  2. Stage 2 (failsafe activated): GPS Rescue takes over
  3. Climbs to gps_rescue_angle (configured as approach angle, not altitude directly — see below) while heading toward home
  4. Navigates home using GPS position
  5. Descends and lands when over the home point
  6. Disarms on landing

If GPS link is lost during Rescue (insufficient satellites), the FC falls back to angle mode with disarm on impact.

Home point and why it matters

The home point is recorded at the moment of arming — the GPS position at that exact instant. This has two important implications:

  1. Walk then arm: if the pilot arms the drone and then walks away to fly it remotely, GPS Rescue will return the drone to the arm location, not to the pilot's current position. Arm from the intended landing/recovery area.

  2. Re-arm after moving: if a flight involves landing at a different location and re-arming, the new home point is the new arm location. No manual home-point update is needed — it always records automatically.

Return altitude

gps_rescue_throttle_hover and gps_rescue_angle together determine the return flight profile. The return altitude must clear all obstacles between the drone's position and the home point. There is no obstacle awareness in GPS Rescue — it flies a straight line at the configured approach.

For each deployment: estimate the maximum obstacle height along the return path, add at least 10 m clearance, and set the return altitude accordingly. The default configured in the base diff (return profile conservative for open terrain) must be reviewed before flying near structures, trees, or antennas.

Minimum satellite requirement

gps_rescue_min_sats = 8 means GPS Rescue will not activate unless at least 8 satellites were visible when the drone was armed. If fewer than 8 satellites are available at arm time, GPS Rescue is silently disabled — link loss will cause the drone to enter angle-mode failsafe instead of returning home.

The OSD should display satellite count at all times. Do not arm with fewer than 8 satellites visible if GPS Rescue is operationally required.

Reference

GPS Rescue configuration parameters (base diff values)

Parameter Value Notes
failsafe_procedure GPS-RESCUE Activates GPS Rescue on link loss
gps_rescue_min_sats 8 Minimum satellites at arm time
gps_rescue_angle 32 Approach tilt angle (degrees)
gps_rescue_throttle_min 1150 Minimum throttle during rescue
gps_rescue_throttle_max 1700 Maximum throttle during rescue
gps_rescue_throttle_hover 1400 Hover throttle estimate for rescue
gps_rescue_sanity_checks RESCUE_SANITY_ON Abort rescue if behaviour is unsafe

GPS Rescue pre-flight checklist

  • Satellite count ≥ 8 before arming (check OSD)
  • Arm from intended recovery area
  • Return altitude configured for local terrain and obstacles
  • GPS Rescue manually tested at low altitude on first deployment at new site
  • Battery sufficient for full return distance plus descent

Testing GPS Rescue

On first deployment at any new location, test GPS Rescue manually:

  1. Arm and fly to 15–20 m altitude and 30–50 m from arm point.
  2. Activate GPS Rescue via SE switch (manual trigger).
  3. Observe: drone should orientate toward home, maintain altitude, and approach the arm point.
  4. Regain control via SE switch (releasing manual trigger restores RC control).
  5. If rescue behaviour is incorrect (wrong direction, wrong altitude): land immediately and review GPS Rescue parameters and home point.

Procedure

Adjusting return altitude for a new site

  1. Identify the highest obstacle along the likely return path (trees, buildings, powerlines, terrain).
  2. Estimate its height above the arm point.
  3. Set gps_rescue_throttle_hover to a value that produces altitude approximately 10–15 m above that obstacle.
  4. Calibrate gps_rescue_throttle_hover by flying to the target altitude and reading the OSD throttle value in hover. Set the parameter to this value.
  5. Document the site-specific value. Reset to the conservative default when moving to a new site.

Rationale

Why RESCUE_SANITY_ON is mandatory

Sanity checks abort GPS Rescue if the drone is not moving toward home or is descending outside the home zone. Without sanity checks, a GPS Rescue activated near the edge of available satellite visibility could cause the drone to fly in an incorrect direction indefinitely. Sanity checks are a safety backstop — they cause GPS Rescue to abort and disarm rather than fly the drone further from home if something is clearly wrong.

Connections

requires: - betaflight-setup - gnss-gps related: - betaflight-profiles - closed-loop-control - ardupilot-failsafe leads_to: - pid-tuning-rate-profile