Queen Mary 2 - Service Speed

[Rob Lightbody]

As I understand it, a ship's service speed, is the speed its designed to do a lot of the time.  It is always lower than the top speed, because if the service speed was the same as the maximum speed, the ship would be late arriving all the time in case of any snag, even a late departure.

QE2's service speed, like her 2 predecessors, was designed to be 28.5 knots exactly.  She could go 30 knots+ to allow for contingencies.  This remained the same after re-enginging because the crossing time was unchanged in 1986, but with increased redundancy (she could maintain that with at least one engine offline for maintenance).

The new Queen Anne is showing as 18 knot service speed, 22 knots max, which makes sense in the new world of expensive fuel and no rush to get anywhere.

But what is QM2's *real* service speed?  By the time she came along, crossings were already longer, and 28.5 knots wasn't required.  I would contend that her service speed is whatever she can do without the gas turbines running - they are her contingency for when she needs to go faster.

[Thomas Hypher]

She can do up to about 24 knots without her gas turbines as I understand. The 7 night crossings requiring an average speed of around 21 knots if I recall correctly.

She was designed for the 6 night crossing with it's average crossing speeds of 25 to 26 knots, the gas turbines giving her the headroom to make up delays by allowing her to get up to 28/29 knots if needed (not as an average speed or service speed mind) under normal sailing loads - also not the 29.63 knots knots she achieved on sea trials, with light loading and unfinished, after correcting for sea and weather conditions according to Stephen Payne at the time. Furthermore, one of her former deck officers (Holynougat here on the forum) I think stated a while ago that her 4 main diesels have had load limits placed on them in the years since she entered service - with the impacts on top speed that would have.

If I had to guess I'd say her service speed if the bean counters (accountants) had no say, would still be her old 6 night crossing speed of 25/26 knots where one gas turbine would be online (as I remember hearing when putting my ear to the funnel deckhouse during those 6 night crossings) and then the second gas turbine would provide the electricity for making up delays up to about 28/29 knots but not more given a load of passengers, fuel, etc etc unlike on her sea trials.

If I ever serve on her as a deck officer I will probably find out the reality as part of the job - without the above approximations and guesswork, and if not I'd find out - out of curiosity and would share what I learn here if I'm allowed to do so.

[Rob Lightbody]

Thanks Thomas.  I think your thinking is aligned to mine.

You said you heard a turbine running when you were aboard, however you can't be sure of the reason - they must also have to run them if they are doing maintenance on a diesel?

It would be nice, while aboard, to be able to get more technical information - e.g. what engines are running and why, what is the current power output etc.  Would be great to have this in the viewing room behind the bridge, and on the in-cabin telly.

[Thomas Hypher]

We were going over the speed at which I am pretty sure they kick in (24 knots), as we were on a 6 night crossing at the time, so I think it was most likely supplementing the 4 main diesels to maintain the 25/26 knot average crossing speed. However, as you mention it could've also been filling in for a diesel, although I gather the 4 main diesels don't get that much downtime (which might explain why the load limits were put in place on them if they are in use most of the time except downtime where needed in port). Her 4 main diesels really don't get a break these days either, with the very sparing use of her gas turbines as I understand it due to fuel costs for them.

That would be very cool if this information was displayed in the bridge viewing gallery and on the TVs. Imagine if that had been done on QE2 - one could've anticipated particularly high speed passages!