Overview

The CRASH parameter group configures the automatic Crash Detection logic. This safety feature is designed to rapidly identify when the vehicle has impacted the ground or an obstacle and is no longer under control.

Upon detection, the system immediately Disarms the Motors to:

1. Prevent fire (stalled motors overheat ESCs).
2. Prevent injury to bystanders.
3. Minimize damage to the airframe and props.

Key Concepts

1. Detection Logic

Different vehicles use different logic:

• Plane: Looks for sudden X-axis deceleration (impact) while flying (CRASH_ACC_THRESH).
• Copter: Looks for a sustained error between Target Angle and Actual Angle (loss of control) combined with low throttle usage.

2. Check Logic (CRASH_DETECT)

(Note: Often CRASH_ACC_THRESH or FS_CRASH_CHECK).

• If enabled, the code runs in the fast loop to monitor IMU spikes.

Parameter Breakdown

• CRASH_ACC_THRESH: (Plane) Impact force threshold (m/s/s). 0 to disable.
• CRASH_DETECT: (Some firmwares) Bitmask options.

Integration Guide

• False Positives: If you hand-launch or use a bungee, ensure CRASH_ACC_THRESH is high enough not to trigger on release.
• Rough Landings: If the plane disarms the moment it touches down (but bounces), you might need to relax the threshold or improve the landing flare logic.

Developer Notes

• Library: Vehicle specific (ArduPlane/crash_check.cpp).
• Safety: This is a critical safety feature for large/heavy drones.