Detects when a rotary-wing vehicle drops more than FD_ALT_LOSS metres
below a NED-z reference while altitude control is active,
and immediately triggers flight termination (parachute deployment).
Detection (FailureDetector):
- FD_ALT_LOSS: drop threshold in metres (0 = disabled, default)
- FD_ALT_LOSS_T: hysteresis time
- Guards: rotary-wing only, altitude control active, z_valid, setpoint
fresh (<1 s). Manual, Acro and FW/VTOL-FW modes are excluded.
- Ratcheting reference: initialises to lpos.z on first sample below
setpoint, preventing false triggers on new waypoints
Failsafe action (commander):
- New fd_alt_loss flag in FailsafeFlags.msg
- COM_ALT_LOSS_ACT: -1=Disabled (default), 0=Terminate
- Terminate fires immediately, cannot be overridden, and never clears
until disarm (parachute deployment is irreversible)
gguidone
68e47df055