Titanic’s Evasive Maneuvers

[Samuel Halpern]

This part is even more difficult to understand than the claim that the Titanic was holding-up the iceberg. By the time QM Rowe saw the iceberg from his position on the poop deck, it had long lost contact with the ship. So, how could the Titanic still be "supporting" it?

Arun, you are applying logic to a problem.

 

[Arun Vajpey]

Arun, you are applying logic to a problem

I thought most people did?

 

[Arun Vajpey]

Sam, I requoted the excerpt below from your post on the other ongong thread and posted it here as it was more appropriate.

Lightoller also said at that trial that he thought the ship could have missed striking the berg when first seen at 500 yards if Murdoch would have by whipped the wheel hard over and reversed port side engine.

I do not believe that Lightoller or anyone else could have avoided an impact that night. Apart from the fact that given those conditions (darkness, ship's speed etc) it was already too late when the berg was sighted, there is only so much even the best trained Officer can think and do in an emergency. I believe that Murdoch did the best he....or anyone else, could have done.

But I want to discuss the possible outcomes of that hypothetical scenario outlined by Lightoller in the quote above.

@Samuel Halpern has described various hypothetical "Situations A to F" on pp115-122 of PTAA (Chapter 12) with a related illustration Fig 12-02. They are all related to likely outcomes if Murdoch had given his first helm order - Hard a starboard - earlier or later than he actually did with 'Situation D' being closest to actual events. But I think the outcome of 'Situation B' (which is actually one where the helm order came just 5 seconds after the 3 bells) can be extrapolated into what might have happened if Murdoch had reversed the port engine at the same time as he gave the hard-a-starboard order. If he had done that, the bow might have swung to port quicker and sharper than it actually did but the maneuver would also have swung the stern section more towards the iceberg. In that case, the second helm order to port might not have succeeded in swinging the stern clear of the berg and an outcome similar to or very close to Sam's 'Situation B' might have occurred.

In that situation, the bow swings away from the iceberg in time but with the stern going the opposite way, the iceberg impacts further aft, in the vicinity opposite the 4th funnel near the juncture between the reciprocating and turbine engine rooms. If that had happened, Sam illustrates that the resultant damage would have resulted in a flooding of at least 3 'critical compartments' and loss of the ship. What I want to ask Sam is the change in the flooding and sinking timescale and chain of events with that Situation B scenario.

• With the very likely damage to the dynamo room, would there have been an early power failure, resulting in most of the ship plunged into darkness and wireless failure?
• With those 3 critical compartments flooding, would there have been the risk of the Titanic capsizing?
• Overall, how long would the Titanic have taken to sink completely under that Situation B scenario?

 

[Richard C Elliott]

@Arun Vajpey I, too, would be interested to hear @Samuel Halpern's thoughts on the effects of reversing the port engine. The two questions in my own mind are how much the differential engine power would augment the effect of the rudder and where the new pivot point of the ship would be located.

On the first point I am thinking that the reversed engine would diminish the net rearward flow of water over the rudder, particularly on the more effective side, so how much would it really change the rate of turn. Differential engine orders are very effective at low speed where the rudder is less effective but I am uncertain what would happen at high speed. Do you have any information on this Sam?

The second point is that the rudder acts mainly by producing a lateral force at the stern which pivots the ship about a fulcrum much further forward. The differential engine use creates a turning couple between two opposing longitudinal forces which should actually be at a maximum directly between the two props. To put it more simply the rudder acts by swinging the stern sideways, the differential engine couple acts by twisting the stern around. The pivot point is not likely to be the same. Around what point does the whole ship turn when you combine the two. Again I'm hoping Sam can offer some pointers on how we analyse this.

 

[Arun Vajpey]

On the first point I am thinking that the reversed engine would diminish the net rearward flow of water over the rudder, particularly on the more effective side, so how much would it really change the rate of turn.

Of course, I am only assuming that a hard starboard helm order along with reversal of the port reciprocal engine would have resulted in a scenario very close to "Situation B" described in his book starting from Fig 12-02. Let us wait and see what Sam says.

 

[Richard C Elliott]

Of course, I am only assuming that a hard starboard helm order along with reversal of the port reciprocal engine would have resulted in a scenario very close to "Situation B" described in his book starting from Fig 12-02. Let us wait and see what Sam says.

Sorry if I appeared to be criticising your idea. That wasn't intended. What we both really want to know is, indeed, how the use of the port engine might alter the "Situation B" scenario. I'm just saying that might not be simple to calculate. Over to Sam.

 

[Samuel Halpern]

Haven't had much time to go into this, but for those who do not have my book, Prelude
let me put here a copy of Situation B from Fig 12-02 so everyone can follow what you both were talking about:

Excluding the timing shown above, I think it would be les than 55 sec if the port engine was reversed, the bow would twist faster but the stern would still be somewhat exposed. The pivot point instead of being about 1/3 back from the bow, would be much further back. I'm guessing about amidships if not a little further aft. This type of maneuver was used to negotiate the sharp reverse S curves coming down from Southampton water into the Solent when under pilot command. And yes they would be going at reduced full-ahead speed for restricted waters, around 20 knots in straightaway stretches. I know this from studying transcripts of the Olympic/Hawke trial. There the idea was take sharp turns around navigation buoys in a channel.

For a sharp turn to port, such as turning the West Bramble buoy, they would first give the order for slow on the port engine (turbine was disengaged) and starboard easy on the helm as they came up to the buoy. When the buoy was abeam, they would order stop-port (engine), and hard-astarboard on the helm. Then half astern port, followed by full-astern port as the buoy was being rounded. All the while, the starboard engine was going full ahead. As they approached the end of turn they would order the helmsman to steady on a particular compass course and the order stop-port engine (which had been running in full reverse. This was soon followed by full-ahead port, and the turbine was then connected back up. The entire procedure just described took around 4 to 5 minutes. And of course the engine room was on full standby all along, and they didn't have to worry about the stern swinging out and striking something as dodging an iceberg would have.

My own belief is that a port around attempt such as I showed in Fig. C-01 in App C would have worked, but it required an unrealistic reaction time (like 5 seconds) and perfect judgement of distance from the moment 3 bells were heard.

 

[Arun Vajpey]

I think it would be less than 55 sec if the port engine was reversed, the bow would twist faster but the stern would still be somewhat exposed. The pivot point instead of being about 1/3 back from the bow, would be much further back. I'm guessing about amidships if not a little further aft.

Thanks Sam. OK, since Lightoller did not say anything about Murdoch giving the first helm order earlier during that conjecture of his, we are not talking exactly about your Situation B but a different hypothetical one where the 1/O gave the helm order at exactly the same moment as he actually did but also threw the port engine into reverse at the same time. I assumed that the pattern of the ship's swing would then be closest to what you have depicted n Situation B, albeit for different reasons.

By what you are saying in that quote above, I understood that if it had happend that way, the bow would have turned to port faster but the stern would have swung towards the berg and the iceberg would have impacted amidships or a but further aft (between the 3rd and 4th funnels?). Also, because of the more acute angle of the turning ship during the impact, would the extent of damage have been still over 200 feet along the starboard side? If so, there was still the risk of early flooding of the dynamo room and resultant lower failure?

Also, from what I remember about your situational differences and related outcomes, I think flooding of the amidships area could have resulted in early loss of transverse stability and increase the risk of the ship capsizing.

 

[Richard C Elliott]

Excluding the timing shown above, I think it would be less than 55 sec if the port engine was reversed ...

The next question though is how quickly the port engine could be put into reverse. I think the scenario Arun has in mind is that Murdoch gives the engine telegraph order simultaneously with the helm order. My recollection is that it would take the engineers something like 10-15 seconds just to start backing an engine, even if they were on standby, and possibly a minute or so before it was developing full astern power. So a significant chunk of that original 55 seconds would have passed before the engine reversal was having much effect. I get the feeling that the total time wouldn't be a lot less than 55 seconds.

 

[Richard C Elliott]

By what you are saying in that quote above, I understood that if it had happend that way, the bow would have turned to port faster but the stern would have swung towards the berg and the iceberg would have impacted amidships or a but further aft

I think you may have misunderstood. Sam thinks the pivot point would be amidships or further aft, instead of 1/3 back from the bow. If the pivot point is moved aft the bow turns faster and the stern swings less. Without drawing it to scale I think it is hard to say where a strike would occur in scenario B.

It sounds at first hearing like the 'port around' manoeuvre should be a little more achievable with the ship pivoting further aft, but then you realise that he would be starting the starboard turn from a situation where he had reversed the port engine so in the limited distance and time available it probably just makes it far more difficult.

 

[marina_irc]

This diagram from the 1960s naval deck officers correspondence course in Naval Shiphandling may be useful reference for those following along.

 

[Arun Vajpey]

I think you may have misunderstood. Sam thinks the pivot point would be amidships or further aft, instead of 1/3 back from the bow. If the pivot point is moved aft the bow turns faster and the stern swings less.

Yes, I agree that I misunderstood what Sam said in his post #277, mistaking the 'pivot point' for the point of impact. But I am having trouble understanding the physics behind the highlighted part of your post above; with the Titanic being a longitudinal rigid structure, how can the bow swing more and the stern less? Did you mean the relative to the iceberg less of the aft part of the ship would be exposed to the closing iceberg if the pivot point was further aft than it actually was?

I ask because as I understand it, if the bow swings 20 degrees to the port from the long axis of its original path, then the stern has to swing 20 degrees to starboard in relation to the same direction.

Without drawing it to scale I think it is hard to say where a strike would occur in scenario B.

Well, in Sam's actual 'Situation B' Murdoch yells the "Hard-a-Starboard" order only 5 seconds after the 3 bells in which case Sam has illustrated (in his book and in Post #277 above) how the bow would have missed the berg but the impact would have taken place closer to the stern, perhaps in the vicinity of the 4th funnel. That would have resulted in critical flooding of 3 compartments, almost certain damage to the dynamo room with possible early power failure affecting the lights and wireless among other things. Not sure of the capsize risk with that scenario.

But the hypothetical scenario quoted by Lightoller implied that Murdoch issued the helm order at the same time as he actually did, ie about 15 seconds after the bells, which we now know was because he needed that time to assess the situation and calculate his maneuver. The difference is that Lightoller suggests that he could have thrown the port reciprocating engine into reverse at the same time, which according to the former 2/O, would have avoided impact. But look at your opinion on that:

My recollection is that it would take the engineers something like 10-15 seconds just to start backing an engine, even if they were on standby, and possibly a minute or so before it was developing full astern power. So a significant chunk of that original 55 seconds would have passed before the engine reversal was having much effect.

I would like you to please explain what you meant by a port engine reversal at the same time as the hard starboard helm would not have had much effect before the impact because of the logistics and mechanisms involved. Did you mean that a port engine reversal order given 15 seconds after the bells would not have swung the bow any quicker or further than it actually did OR that there would have been a partial effect, with the bow swinging quicker and a bit further than it actually did. I ask because if it was the latter, it brings us back to the scenario where the bow missed the iceberg (remember, it was a 'just' glancing blow as it was) but impact took place further aft, perhaps around amidships? Then there is the question of how far along the side of the ship the damage from such an impact would have extended; the rearmost limit would certainly have been closer to BR2 and BR1 but I'll leave it to you to work out by how much.

 

[Richard C Elliott]

I ask because as I understand it, if the bow swings 20 degrees to the port from the long axis of its original path, then the stern has to swing 20 degrees to starboard in relation to the same direction.

Sorry, I could have made myself clearer. The angle of swing is obviously the same for both bow and stern but I was thinking of the lateral distance relative to the line from ship to iceberg (or original course, whichever way you like to think about it). The result of the stern not moving so far starboard in the initial phase of the turn would be that the impact (if it occurred) would be even further aft than you suggest. It might even miss altogether which, I think, is what Lightoller had in mind. Thinking about that scenario you would imagine that a 'port around' manoeuvre just before the stern impact should easily clear the stern, but it would be much harder to do at a point when both the rudder and engines are configured for a turn to port.

there would have been a partial effect, with the bow swinging quicker and a bit further than it actually did. I ask because if it was the latter, it brings us back to the scenario where the bow missed the iceberg (remember, it was a 'just' glancing blow as it was) but impact took place further aft, perhaps around amidships?

Yes, I am thinking of a partial effect but as explained above my mental image is of an impact much further aft than you are thinking about. My concern, though, is how much effect the engine order could have in the short available time. If it was only very slight the impact might be further forward, in line with your own thinking.

The worst case scenario of getting the timings of the whole sequence wrong would, I suspect, have been a damaging strike in the machinery spaces as you suggest. Lightoller's suggestion seems rather dubious.

 

[Arun Vajpey]

Lightoller's suggestion seems rather dubious.

It certainly does.

The angle of swing is obviously the same for both bow and stern but I was thinking of the lateral distance relative to the line from ship to iceberg (or original course, whichever way you like to think about it). The result of the stern not moving so far starboard in the initial phase of the turn would be that the impact (if it occurred) would be even further aft than you suggest. It might even miss altogether which, I think, is what Lightoller had in mind.

Thanks for clarifying that point Richard; I like the way you think. But I am not convinced that reversal of the port reciprocating engine could have avoided an impact with the iceberg, all other conditions being the same. I think it would have been the "worst case scenario" that you descrive below.

The worst case scenario of getting the timings of the whole sequence wrong would, I suspect, have been a damaging strike in the machinery spaces as you suggest.

Sam said that he was working on this scenario and I have a feeling that there will be an input from him soon.

 

[Samuel Halpern]

But the hypothetical scenario quoted by Lightoller implied that Murdoch issued the helm order at the same time as he actually did, ie about 15 seconds after the bells,

Nobody knows what Lightoller was thinking. He and other ship handlers knew that a ship will twist faster if one engine is reversed. But I don't think he thought everything out. Of course the engine room was not ready for any emergency maneuvering actions when the accident occurred, so this is purely of academic interest. To analyze something like this requires knowledge of the maneuvering characteristics of the ship which the conditions of one prop reverse with the other ahead. I haven't seen data on that. I did, however, have data on the turning of Olympic with helm hard over at full ahead, and documented that in: http://www.titanicology.com/Titanica/Two-Points-in-Thirty-Seven-Seconds.pdf
from which I was able to to derive the drawings shown in post #277 above.