Deborah,
These are very good questions you ask. But to answer your primary question, what was the ship doing at 11:40 when she collided with the iceberg? The answer is that it looks like she was doing the same as she was at 10 p.m., 22 1/2 knots through the water. The fastest speed of her short voyage.
It seems that other than
Boxhall, Titanic's other surviving officers tried to downplay the speed that Titanic was going at when she collided with the iceberg. Going through the testimonies, it seems
Lightoller put it at 21 1/2 knots along with Pitman. Lowe downplayed it further to 21 knots.
Boxhall was the one who said he used 22 knots in calculating his distress coordinates. He also said that he didn't have the latest engine revolutions that watch, meaning the 8 to 12 watch, when he worked the position out. But he was also on duty during the first 'dog watch' from 4 to 6 p.m., and we know the ship was then doing 76 rpm at 4 p.m. from leading firemen Hendrickson who was told that by the 2nd engineer when he came on duty at that time. It is likely that Boxhall had that information when he went off watch at 6. That told him the ship's engines were still doing 75 to 76 rpm as they were since Saturday. Between noon Saturday and noon Sunday the ship traveled 546 miles in 24 hours 45 minutes for an average speed made good over ground of 22.1 knots. That is why he used 22 knots in his work, especially since he noticed the sea was smooth as he said.
By the way, in 1935
Lightoller wrote in his book '
Titanic and Other Ships' that Titanic was making an easy 22 knots that night.
Between 8 and 10 p.m. the taffrail log showed the ship ran 45 nautical miles according to QM Hichens who got the log reading at a half minute to 10 just before taking his trick at the wheel. That is a measured speed through the water of 22 1/2 knots for that two hour period. We also have evidence that two additional boilers were hooked up at 7 p.m. which would have resulted in increased engine revolutions. And it has been documented that many passengers noticed an increase in engine vibrations that night before the accident took place.
When the accident happened, QM Rowe took the reading on the taffrail log that showed that ship ran 260 nautical miles since noon when the log was reset. Now 260 miles in 11 hours and 40 minutes is an average speed through the water of 22.3 knots. That is exactly what you would expect to see if the ship was doing about 22 knots before 7 p.m. and then did 22 1/2 knots after 7 p.m. up to the time of the accident.
As far as who sets the speed, it is the Captain in consultation with the Chief Engineer. According to Lightoller the officer of the watch did not necessarily know the exact number of revolutions carried unless he chose to inquire. As OOW he of course knew that the engines were being run at full ahead as indicated on the engine-order telegraphs, but the average number of revolutions was something that was recorded at the end of each watch, and the OOW can get that information if they cared to. Since the task of working out the ship’s dead reckoning position was usually left to one of the junior officers, it should not come as a surprise if the OOW was not too concerned about knowing such details.
