Uncrew C2 Loss

Andi Lamprecht ·2026-05-11· 3 min read· Draft

INDICATIONS

1. Uncrew announces “C2 Lost”, Red aircraft indicator
2. Uncrew GCS unresponsive for greater than 6 seconds

POSSIBLE CAUSES

1. Server failure
2. Hardware failure

FAILSAFE BEHAVIOR

If communication with the Uncrew server is lost, the onboard Uncrew application uses built-in logic to safely return the aircraft to the home point. When the application detects a loss of comms with the Uncrew server, it waits 45 seconds for communication to be regained.

After 45 seconds of lost comms, the onboard application checks the winch status. If the winch is locked, the system commands a Return to Home. If the winch is not locked, the onboard application waits an additional 30 seconds to allow the winch delivery to complete. After 75 seconds total, if the winch remains unlocked, the system sends a retract command to the winch. The onboard application then waits another 30 seconds to allow the winch to fully retract and lock. If the winch still is not locked after a total of 105 seconds from the initial loss of comms, the system sends an unspool command and initiates Return to Home.

When the FMU loses communication with the Skynode while in Mission or Hold flight mode, the PX4 autopilot engages a Return to Launch (RTL) failsafe using the previously planned mission path, after a loss timeout period of five (5) seconds. If the FMU maintains communication with the Skynode but the Skynode loses connection with the Uncrew server, refer to the Uncrew Loss of Comms failsafe.

PROCEDURE