What is a propeller curve?
Short answer
| Aspect | Relation | Use |
|---|---|---|
| Power vs RPM | P ∝ N³ | Engine load setting |
| Torque vs RPM | Q ∝ N² | Governor droop matching |
- Definition: a plot of the torque (or power) a fixed‑pitch propeller demands versus its rotational speed for a fixed propeller pitch, as the ship’s speed rises and falls with the propeller speed
- Shape: power ∝ N³ (cubic), torque ∝ N² (quadratic)
- Basis: propeller hydrodynamics via advance coefficient J and coefficients Kt, Kq
- Use: engine–propeller matching; intersection with engine torque curve gives the operating point
- As Second Engineer: verify the curve is used for load analysis and fuel consumption estimates; ensure the governor and pitch settings keep the engine on the curve
Full answer
The full answer explains each point step by step, with the regulations and figures behind it and the discussion from other candidates. It is in the MEO Class II section of the Marine One forum, open to members enrolled for the MEO Class II exam.