MARCHWOOD SIMULATION

　

1) The UK's MAIB are investigation the near miss between Bro Axel and fishing vessel Nordhinder, followed by the subsequent grounding of Bro Axel on the morning of December 5^th, 2002 whilst departing from Milford Haven.

　

 The MAIB approached Warsash Maritime Centre in order to assess, through simulation, the likelihood of avoiding the grounding by taking action different from that taken by Bro Axel in the heat of the moment, having just missed the fishing vessel Nordhinder.

　

 The incident was reconstructed on both ship bridge simulators of Warsash Maritime Centre. The report is concerned with reconstruction on the Full Mission Ship's Bridge Simulator located at Marchwood Southampton.

　

2) The Simulator

 The equipment is a Norcontrol NMS 90 mark 111 utilising the Norview 2000 visual system. There is a projected view from the bridge of 210°with viewing around a full 360° available using a scanning monitor on the bridge.

　

3) The Database Area

 The reconstruction was undertaken in the "Haven" database that has been used for several years by WMC for, amongst other tasks, the training of Milford Haven pilots and also the reconstruction of the "Sea Empress" casualty. It is kept up to date from weekly Notices to Mariners and information from the Harbour Master.

　

4) The Environment

 The relevant tidal times and heights were obtained from the Port Authority which, once entered into the simulator system, would produce the expected tidal directions and rates at the time of the incident together with tidal heights above datum.

 The current was expected to be flooding along the line of the channel where the incident took place, at about 1.5 knots.

 The wind was reported as being NW'ly, force 3. Accordingly a wind direction of 310°at a speed of 5m/s, gusting ±10%, was used for the simulation.

 Time was based on the Nordhinder track plot, since there is no agreed time between Bro Axel, Nordhinder and Milford Haven VTS.

　

5) The Mathematical Model

 The Model used in this reconstruction was the nearest in configuration to the Bro Axel that was available in WMC's portfolio. No mathematical model of Bro Axel suitable for running on the NMS 90 system is known to exist. A model of "Ellen Knutsen" is in the Norcontrol library; this model as similar in size but does not necessarily have the same manoeuvring characteristics as the Bro Axel. This model would have to be purchased and then evaluated and may not produce results different from those obtained with the model used.

　

　

 Although the Bro Axel has a 60° Becker Rudder, only 15°rudder was in fact used in the incident. Where a hard over rudder order has been used to assess possible alternative action, then a maximum of 35°has been used. Bro Axel may well have been able to use more rudders in the event.

　

6) The Reconstruction

 Basic details were provided by the MAIB. These included a copy of the Transas track plotter taken from the Nordhinder showing her position every 10 seconds up the East Channel to past the "Esso" buoy. This was used to reconstruct the track of the Nordhinder as faithfully as possible. It was also used to gain an estimation of track and speed being made good.

　

　

 This track as considered fairly accurate, for example it is known that the Nordhinder hit the "Esso" buoy and this clearly shows on the plot.

 The evidence for the track of the Bro Axel was more anecdotal. Screen shots of the VTS recording of her track show that she was on the northern edge of the channel. The master is reported as saying the speed was about 9 knots, and this has been taken to be the ground or GPS speed. With a 1.5 knot current against her it was assumed that the Bro Axel was making a water speed about 10.5 knots.

　

 For the purposes of this reconstruction, initial action by the Bro Axel, a "Port 15°" rudder order, was taken when Nordhinder was on Bro Axel's starboard side and was showing both sidelights whilst swinging from port to starboard. This event appears to take place at 03:42:13 in the simulator. The distance between the two vessels appears to be about 5 cables at this moment.

 The second action "Full Astern" was taken when the Nordhinder was clearing the starboard side of the Bro Axel. It was reported as missing by "30 metres".

　

7) The Simulator Runs

 Several runs were taken once the reconstruction had been fine-tuned.

　

Run 1 - Reconstruction of events as described

@ 03:42:13 order rudder Port 15°

@ 03:43:33 order full astern, (rudder remains at Port 15°)

　

Run 2 - Ordering 35° starboard rudder in lieu of the Full stern order, engine RPM remaining same

@ 03:42:13 order rudder Port 15°

@ 03:43:33 order rudder Starboard 35, (engine rpm not changed)

　

Run 3 - Ordering 35° starboard rudder in lieu of the full astern order, and increasing engine RPM, once the rudder past the amidships position, to increase rudder effectiveness

@ 03:42:13 order rudder Port 15°

@ 03:43:33 order rudder Starboard 35°, (increase engine rpm)

　

8) Conclusions

 Ii is likely that had the Master of the Bro Axel ordered Stb'd 35°, (or better with the Becker rudder) instead of full astern, then he would have likely kept in the channel or perhaps passed just south of the "Chapel" buoy, where there was sufficient water to stay afloat at the state of the tide.

 Had the Master given this starboard rudder order and increased his Ahead RPM then he would likely have passed safely to the north of the "Chapel" buoy and been able to resume his planned departure track without further incident.

　

 It should be noted that the concept of "hard to stb'd and "Full Ahead" may not be instinctive, nor without hesitation in a critical situation unless the conning officer has had proper ship handling and/or emergency procedure training.