ANALYSIS OF MAJOR MARINE DISASTERS
Case Studies of TITANIC and Cruise-Ship-Grounding
Prof.Haruzo Eda, US Merchant Marine Academy, USA
Masayoshi Numano, National Maritime Research Institute, Japan
Abstract: Computer simulation analysis was applied to examine two major maritime disasters, i.e., the TITANIC collision with an iceberg in 1912 and a recent 700 ft cruise ship grounding in 1994. Between these two incidents, certain similarities existed in circumstances, high-speed hull-form design, and rudder-propeller arrangement. On these two ships, the officers executed collision-avoidance maneuvers, i.e., the full rudder and full astern commands prior to the collision. The TITANIC had unique design configurations at the stern, having three propellers and a single rudder. The cruise ship had a single rudder and twin propellers. Such propeller-rudder arrangements made the ships' rudders inherently ineffective. On the basis of design configurations, computer models of maneuvering characteristics were developed for these ships. In the computer simulation runs, trajectories at the time of incidents were reconstructed. In the subsequent simulation runs, twin Flap-rudders behind propellers were employed to these ships. This rudder-propeller arrangement proved to be very effective in critical maneuvers on these two ships, making collision-avoidance maneuver successful. Determining exact causes and conditions at the time of mishaps is very useful in learning what can prevent similar errors from re-occurring. Furthermore, runs similar to this study could be used in simulator training sessions.
Figure 1 The TITANIC
A ship, the largest man-made moving structure on the earth, is capable of carrying a huge amount of cargo or many passengers on board. When a ship experiences a mishap such as a collision, grounding, capsizing or sinking, the consequences are enormous. Computer simulation analysis was applied to examine two major maritime disasters, namely the TITANIC collision with an iceberg in 1912 and a recent 700 ft cruise ship grounding in 1994. Between these two incidents, certain similarities existed in some circumstances, high-speed hull-form design, and rudder-propeller arrangement.
The TITANIC had unique design configurations at the stern, having three propellers and a single rudder (see Figures 1 and 2). The cruise ship had a single rudder and twin propellers. Such propeller-rudder arrangements made the rudders inherently ineffective. On the basis of design configurations, computer models of maneuvering characteristics were developed for these ships. Then, trajectories at the time of incident were reconstructed in simulation runs.
Current cruise ship designs have been actively employing flap-rudders and rotative-pod-propellers with superior maneuvering performance. Accordingly, these devices were employed in the subsequent simulation analysis for comparison. flap-rudders located behind propellers made successful collision-avoidance maneuver on the TITANIC and a 700 ft cruise ship, i.e., no collision with the iceberg or grounding.
2. TITANIC COLLISION WITH ICEBERG
In the late evening of April 14, 1912 on her maiden voyage from Southampton to New York, TITANIC was proceeding west at a cruising speed of approximately 23 knots in the northern Atlantic Ocean. The ship was 883 ft long and 92.5 ft wide (see Table 1) and was carrying 1,316 passengers and 891 crew members.
Table 1 Major Dimensions of SS TITANIC
Length overall 882'9"
Lp, Length betwn pp 850'0"
Beam extreme 92'6"
Depth to bridge deck 73'3"
Total height to bridge 104'0"
Draft loaded 34'6"
IHP of reciprocating engines 30000
SHP of turbine engine 16000
Side propeller diameter (two) 23'6"
Number of blades 3
Center propeller diameter 16'6"
Number of blades 4
On that day, many iceberg sightings were reported. Accordingly, Reginald Lee and Fredrick Fleet were assigned as lookouts positioned in the crow's nest on the fore main mast. The seas were calm with no wind. The night was clear with no moon. Under such conditions, without the aid of binoculars, (needless to say radars and night-vision binoculars did not exist in 1912), it was difficult to see the presence of icebergs in the distance. When they noticed the iceberg ahead and phoned the navigation bridge, the distance to the iceberg was less than that = 3 ship lengths. First Officer William Murdock ordered full port rudder and full astern to avoid the collision with the iceberg. The ship slowly started to turn towards the port decelerating its speed.
The TITANIC's trajectory prior to the contact to the iceberg was reconstructed in computer simulation runs.
The ship had unique design configurations at the stern. As shown in Figures 1 & 2 and Table 1, the ship had three propellers and a single rudder. The center propeller had a diameter of 16.5 ft powered by a 16,000 HP turbine engine. Twin wing propellers had a greater diameter of 23.5 ft powered by 30,000 HP reciprocating engines. A single rudder was positioned behind the center propeller. This propeller-rudder arrangement provided a relatively small amount of propeller stream flowing into the rudder, making the rudder relatively ineffective compared with more popular stern configurations such as a single propeller-rudder design that provided stronger propeller stream towards the rudder.
The turning performance of the TITANIC was similar to that of high-speed containerships built in more recent years, because a similarity exists in both ships' design configurations (see Figure 3). In 1970, eight 880 ft long and 106 ft wide high-speed containerships called Sea-Land 7 were built. The SL-7 ships had twin-propeller and single-rudder arrangement powered by 120,000 HP with cruising speed of 33 knots. H. Eda had an opportunity to conduct an extensive research on the SL-7 ship's maneuvering performance at that time. Maneuvering characteristics of the SL-7 was determined through model testing in the rotating-arm facility (see Figure 4). Turning trajectory of the TITANIC determined in this paper was similar to that of SL-7.
Figure 2 Stern Configuration of the TITANIC
Figure 3 Similarity of Hull Form(e.g., Length-Beam Ratio) Between TITANIC and SL-7