Answer
Surveyors frequently ask candidates to differentiate between these two deceleration tests, as they test entirely different limits:
| Feature | The Inertia Test (Coast-Down) | The Crash Stop Test |
|---|---|---|
| Propulsion Action | Zero Propulsion. Engine stopped/declutched. Propeller is passive or windmilling. | Maximum Astern Propulsion. Engine run full astern to actively brake the ship. |
| Forces Evaluated | Pure passive hydrodynamic drag and hull resistance. | Maximum structural, thermal, and mechanical stress on the engine and shafting. |
| Primary Metric | Ultimate dead-ship stopping distance and directional drift. | Absolute minimum emergency stopping distance (Head Reach) using maximum power. |