Progressive trial

A progressive speed trial establishes the speed/power curve by running the ship at increasing power steps, conventionally four double runs at 50, 70, 90, and 100% of the main engine’s MCR. Each step is a double run, two consecutive runs on reciprocal headings over a measured mile, so the mean-of-means method removes the tidal current; a modified Williamson turn returns the ship to the baseline between runs. Speed comes from differential GPS and power from the shaft torsionmeter. The corrected results under ISO 15016:2015 give the speed/power/rpm relationship and the contract speed at the guarantee power. It is the core of the speed-and-power acceptance trial.