Tug Usage With Impaired Maneuverability Simulation Experiment

The investigations described in this report represent a second in a series of investigations planned at CAORF to study the effectiveness of tugs in restricted waterways and the variability in pilot operating procedures. One part of the previous study was concerned with the effectiveness of tugs in assisting an 80,000 DWT and a 250,000 DWT tanker following a complete failure with rudder amidships and a loss of engine power simultaneously, and just before entering a 45 degrees turn. Because such a combined failure is extremely severe and has a low probability of occurring, the present study aimed at more realistic failure conditions on a rudder failure (amidships), or no failure at all could occur at any of the four locations prior to the turn, or four locations in the turn. In addition, the failure could be followed by a recovery in a realistic time period, or no recovery at all. Twelve subjects took part in the experiment; six had tugs available and six had no tugs. They performed a total of 12 runs apiece, and experienced engine and rudder failures with and without recovery and at various locations in an order consistent with the statistical experiment design. The data from the experiment were examined qualitatively and selected performance measures were subjected to statistical analyses. Based on these practically useful observations, conclusions were drawn from both the non-failure and failure runs regarding pilot procedures with helm, engine and tug power in relationship to the type and location of the failure. (Author).