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David Steeper

Clear and concise. Navy Lookout at it’s best. Thanks.


Yes. Very good. I do hope they can salvage testing for Ship Bourne Vertical Landing, maybe move equipment over to QE2. Hopefully doesn’t require months of fine tuning and callibration.

Salty Dog

SVRL, Shipborne Vertical Rolling Landing has been proven and certified already from what I can tell so probably not too great a problem, HMS Queen Elizabeth would be able to perform all else I guess.


SVRL Was done once on QE but not certified none of the necessary data was collected or training protocols developed.


They trialled it, on Westlant 19 with a test pilot. That is an awfully long way from doing it routinely – and more importantly on an operational deck (ie one that isn’t covered in parked aircraft for a kick-off……)

I doubt it will ever become an operational capability.


We are scheduled to receive another 24 F35b between 2023-2026, bringing us up to 47/48 depending on whether the crashed one is replaced.
Post 2026, SoS Def has stated that he has a funding line in place to purchase another 24 aircraft taking us up to 72. Believe this is largely dependent on when/how Blk 4 upgrades progress. After that, who knows, as it’s all linked with future procurement of Tempest!

Andrew Deacon

You usually factor losses into the number you order. Whether it be “accidents” like this or engineering write off.


Fairly sure that QNLZ on CSG 21 had a deck full – even if half were USMC. Routinely had 15+ parked on the roof.

As Deep points our below, the slow force build up (largely driven by a combination of MFTS issues and the continued failure to move from LRIP into FRP for the aircraft contracts) is not helping.

But it will come. As – allegedly – will uncrewed aircraft.


Having done numerous spot analyses over the years you need to distinguish between total capacity (which is around 40 and includes a full hangar) and deck spots which is a lot less.

CSG21 had QNLZ with 15 or so F35 routinely on the roof. Which is a good fraction of the intended deck spot – and plenty to make SRVL a lot more tricky than Wizzer’s couple of days flying trials. No – it wasn’t the full capacity, but that’s not the point I was trying to make. When the SRVL trials were conducted on WestLant 19, there were only 3 or 4 aircraft from the development and test force on the ship. That’s a big empty deck to play with. CSG 21 had most of the portside and bow spots occupied, most of the time.

There are no “trainers” based in the US. What there are are the first 3 UK aircraft, which are used to develop procedures and in clearing new weapons and capabilities.

We will end up (on current plans) with a total force of around 70-75 operational frames with a proportion of that number not in the forward fleet. What is vastly more important is the final number of squadrons in the force, which is currently constrained by the two factors I outlined above and amplified by the fact that the tasking authority (Air Command) has multiple competing priorities, not all of which align with Navy Commands priorities and is trying to serve them with a (currently) small force.

I’m reasonably sure that the UK is the only country outside the US and potentially the Red Sea Pedestrians to have deployed the F35 operationally. Not ideal, but then only a national scandal if you read – and believe – the Daily Mail or (these days) the Daily Telegraph.

Last edited 1 year ago by N-a-B

In what way are the aircraft in the US trainers?
They are test aircraft specially instrumented for weapons data gathering.
By claiming they are trainers you make yourself look very unaware of the true situation.


It could be worse. Imagine if we went down the EMALS catobar and F35C route. We would have a carrier that cannot operate the fixed wing strike aircraft we purchased!

At least with the F35B and STOVL route, we are not in the same position as the USS Ford. Which has still yet to clear F35Cs from using its EMALS.

Allan Desmond

what a Joke comparing the QE to a real aircraft carrier Like the USS Ford.. the British ships are just stupid cheap built to Commercial standards, an still couldn’t get right. The sloth an Cultural Cheapness of the British worker strikes (what 10 years to build type 26 , another simple basic ship that’s state of the art in 2005 )


They have proven SVRL’s can be done at low weight in very benign conditions. In reality just a proof of concept. From what I have read the planned trials were to look at the practicality/safety of turning the concept into an operationally useful technique.

Bob M

agree excellent analysis


Still not satisfied with explanation in face of 24h delay in departure, issues with motors. Seems there might be more.


Second your compliment! In addition, quite impressed w/ the erudition of some who chose to comment: believe there are shipyard execs, marine and design engineers, maintenance supervisors and almost innumerable operators w/ in depth experience lurking on this site. Well advised not to attempt to blow smoke on any naval issue.


Hopefully a very thorough root cause analysis will be done to determine if this is just bad luck, a bad part or if there is something unforeseen in the actual operation on the system V’s the design assumptions that needs to be fixed across all the shafts of the class.

C H James

I suspect it will be the length of shaft too long. should have gone for the pod system


You suspect wrongly. Not least because the stbd shaft is the shorter of the two……

Any other insights? Care to detail the numerous failures of podded propulsion on cruise ships over the years?

Thought not.

ship fixer

Well suspected. And well wrong. Show me the positives of pod systems on a ship this big with it’s mission profile


Not my post. Some dipsh1t trolling.

Just Me

Carry on Cruising

Jack Jacksen

A pure vanity political project that has gone horribly wrong. Britain should be concentrating on the defense of its immediate North Atlantic and GIUK Gap maritime environment and not cruising the world. Money and resources could of been spent far better on something far more useful.


Westlant exercise is in the North Atlantic


I’m afraid history has taught us that problems do not always originate in our own back yard. We are still a big economic power and more reliant on world trade than most, added to which the threats to our way of life are coming from far afield. A strong global navy is and always will be our best defence.

Sailor Bob

But we can’t afford to build a new drydock at Pompey!


It’s not so much we can’t afford to as what you would have to not do to fund it. Defence like all organisations has to make choices and set priorities.

Supportive Bloke

Why spend huge amounts Rd if money building one when two exist that work and a third exists that can be made to work?

The Pompey solution might look good on paper but I suspect the costs would spiral due to ancient dock walls (unstable under that sort of pressure differential) and listed structures.

What we do needed is a dedicated ship building facility with an adjoining ship repair facility built in a large site with room for expansion and built for optimal ship building efficiency.

Mike B

I do believe D lock was being looked at.
Don’t forget the huge investment already made in support facilities and dredging.
The costs could be offset by allowing foreign navies and commercial shipping to use the dry dock.


No. Never in a million years.

Mike B

The Russian’s made the same mistake by not putting in place proper support facilities for their “carriers”.
Now their a laughing stock.


The Russ have support facilities for their single carrier. It’s just they don’t look after either very well.

Fantasies about getting revenue from commercial dockings or even more fancifully foreign navies are just that. You may want to research what became of Fleet Support Ltd and how many dockings and types of ship they managed…..



ship fixer

Yeah. Except these vessels are build for ‘reach’ rather than ‘reaction’. They can be deployed to do exactly what you state, but can also operate in strike, littoral and humanitarian ops modes


Britain needs to be able to influence and keep open the sea lanes that are and always have been the life blood of this nation.

For that you need navel air power.

Every existential threat to this nation has always moved in some way to threaten trade routs and shipping lanes.

Also one of the best defences we could have is a carrier at sea.Every bit of our air defence infrastructure is know and at risk. One of our carriers hiding in the Atlantic is not known or easy to destroy.

We also has one of the largest EEZs in the world, spread from the Antarctic to the north seas, Atlantic to Pacific. So we are by nature a nation that has interests across the globe.

Last edited 1 year ago by Jonathan

No nation has EEZ in Antarctic. All territorial rights extinguished by the Treaty signatories. Anyway you don’t need a carrier or even a frigate to have supervision of your EEZ , a patrol vessel will do ……but wait

Dave Wolfy

Quite right, just as we had no business being in Iraq and Afghanistan.


The terrorists that killed 67 UK citizens on 9/11 were in part trained and coordinated from Afghanistan. We had business in Afghanistan, which you seem to have forgotten . That we stayed too long or invaded Iraq has no relevance to the usefulness of these carriers whatsoever.
As for Jack’s comments these vessels take some of the strain from the USN carriers in providing a genuine strike capability for NATO in the North Atlantic area. This was not so important when the USN was running up to 15 strike carriers but has that number has fallen to 10 and with the rise of China these ships have become very important to the alliance.
As they become fully operational in the next few years they will become ever more important and look like a good investment.


Somebody please send this article to every newspaper in Britain so their articles are not so inaccurate, sensationalist, and just downright wrong!


in the media ‘being wrong pays better and gets more clicks’.

Good to see Navy Lookout and a few others not going down that path

Andrew Deacon

It was worth it for a classic front page out of the Daily Star!

Supportive Bloke

“ Apart from the PR and repetitional damage”

Maybe reputational damage?

The repetitional damage was done by the press repeating garbage ‘from those onboard’ !!

Salty Dog

When it mentions problems with the “GE Motors”, are these the same motors that cause the problems on the Type 45’s or am I just entirely wrong ?

Paul T

Very wrong, the Type 45 issue’s are to do with the Intercooler / Recuperator system fitted to its Gas Turbines, not its Electric Motors.

Salty Dog

OK thanks, I’m no expert on these things, just saw the name GE and Motors which from memory were also fitted to the T45’s and wondered if there was a theme.

Prop chief

The motors never had a fault, they are very similar to the T45 motors (minor differences) , but again its hardly ever the motors that have an issue. The T45 had quite a few issues with the converters that run the motors in the early days, but most of this was just development work.
The motor and drive combination we have on QEC is really excellent and has helped us to remain available and operating despite some failures in tha past.

Salty Dog

Again, thanks for your reply, I read in the Article above that there were reports of problems with the motors before she set sail so I just wondered.


Not that either ,

 is that an external SKF coupling that connects the outer propellor shaft to the drive shaft from the propulsion motors failed.” 

The GE electric motors/ integrated electrical system fault are a separate issue

Its a worry in thats its again an integrated system which supposedly controls the different types of generators – GT or diesel for whole of ship electric supply ( I think thats what it is )
 Integrated Full Electric Propulsion (IFEP) systems for the new Queen Elizabeth class (QEC) carriers. The IFEP comprises all shipboard electrical power generation and propulsion systems and features GE’s Advanced Induction Motor (AIM) technology’

Salty Dog

It does mention the Motors in the Article above “she was experiencing significant problems with her starboard motors” (second paragraph under the heading “Broken Coupling”) together with the coupling that’s why I asked, it’s a question based on the words in the article.

Prop chief

While integrated, it is entirely controllable. The IEP concept really does work well in ships the size of QEC…… Far better than on T45 where it is more compromised by only having 1 motor per shaft and until the PIP (propulsion improvement project) is complete, only having 2 engines that can provide enough power to push the ship. QEC has 6 engines capable of providing power at levels required to push the ship through the water, and these are distributed well, so a far superior version of IEP.
The reported problems with the motors were in fact a symptom of the fault with the coupling. During basin trial the ship demanded 30AH,yet the STBD shaft drove to 60AH before the crew tripped it…. It happened very quickly. This is extremely unusual behaviour as a shaft over achieving when I knows the demand reference is damn right wierd, hence getting GE in to look at it. Although the crew can carry out a level of diagnostic, GE are the experts. They established that there was no load on the motors, hence why they over achieved…. The motors and drives are tuned to respond to the know load of the propeller….
So although the shaft was spinning at 60AH, the propeller was not!

It seems odd that they were allowed to sail like this, but I suspect the cause of this (the broken coupling) was not diagnosed prior to them sailing, hence going to sea….. Being at sea can also aid diagnosis!

Salty Dog

Your reply should be more widely reported as you have explained everything so well. Thanks again.


Could you explain what at AH unit is pleas.


Ahead. The numbers are shaft RPM.


Thank you.


Thanks, that makes more sense- like @Salty Dog I was thinking in Amp hours and wondering what mental gymnastics were needed to make that work easily!


Haha, as long as Jim isn’t involved in any fixing..!
Yeah, I know where you’re coming from with the electric motors- I was thinking similar. Was just trying to work out why they’d use that as a measurement- it’d be a bit like measuring your car RPM via the emount of energy produced by the burning fuel. That’s the gymnastics I was trying to do, and unfortunately neither brain nor body is in good enough shape!

ship fixer

Yeah, but picture yourself in the prop office with WOP, SnrE, SnrW and MEO saying ‘you know what? Maybe the SKF is busted’. It would have never crossed your mind because of the previous reliability of the coupling

Supportive Bloke

I don’t know about that.

I was thinking about it while I was eating my lunch in the sun. And a memory came back…

When you are down in the bowels of a ship you can hear the props in a static test.

I remember a static test on one ship where a prop blade was damaged and the difference in sound between the shafts was obvious as was the vibration.

Here you would have heard cavitation on the working shaft and the rhythmic da-ba-da-ba of the blades passing the hull/rudder. On the shaft free rotating you would hear none of that.

I’m mean this is actually 101 power boat stuff. Has the sheer pin broken if the engine revs and there is no prop noise or prop wake…..

So I’m not sure we quite have the full story yet.

Why would you risk moving a ship which might cause it to drop the shaft and shear off the A bracket in the process.

Something doesn’t add up here as RN guys are not silly.


You won’t be hearing any cavitation – simply because for a low-power, low rpm basin trial, you’re not turning the prop quickly enough to generate such.

Secondly – if you’re in the SCC (which is above the waterline) and your indicated shaft rpm are double that demanded, you’re going to be flapping that the ship is going to break her lines and start hitting things (large expensive things like QNLZ, moored ahead of you). You won’t be listening to props, you’ll be shutting the motor down as quickly as possible, because you really don’t want to do that sort of damage.

Your first suspect will be the MCAS system, because the likelihood of the actual shaftline failure occurring is so low, it simply won’t be on your top 10 suspects list.


Hmm shades of 1941.


The seminal John Belushi comedy?


A very useful comment by a marine engineer at the bottom of the comments wonders if the coupling was disconnected for testing the motors and might not have been reconnected properly ?

Prop chief

Ship fixer is absolutely right, a failed coupling is such a long shot….. Its not common….. If I had the fact that the shaft torque was very low at the same time as the over achieving, I might have gone down the route of ‘is the propeller actually spinning’. But to be honest we’d all be worrying about the fact that the shaft was doing 60 or more when it should have been doing 30, and the fact that if it was doing that there is a very real chance of breaking mooring lines and crashing into other ships (QE)….. So I can understand the desire to test it out at sea rather than alongside.

Also, as others have said, AH is for Ahead…. AS is used for astern…. The problem definitely happened astern as well, but it would have been different because going astern the QEC uses a higher ramo rate than going ahead.
Amp Hours would have been fun, but given we work in mega Watts, it’s more like megawatt-hours!

On the question of disconnecting the coupling for testing, that wouldn’t happen. The shaft can be de-coupled if needed from both motors together and the motors can also be de-coupled from each other too (although only useful if the FWD motor is the defective unit due to the fact that the shaft passes through the AFT motor on QEC), but this is all done internally within the ship, since its far easier than messing around in the water with divers.
Also, it’s not something that is done routinely, it may be done during very specific testing by ship builders and OEMs only!
My final parting thought would be that these couplings don’t really wear out, therefore it has failed for a reason. Some thoughts are….. They have hit something under water during the last stint at sea…. It has broken the coupling, but it has kept turning the shaft due to friction, marine growth and some corrosion….. After a period alongside with the shafts stationary it has sagged slightly and freed up enough that when first turned it broke free.
It may never have been installed right and have chosen this time to fail (properly not that likely).
Similar to bad installation, but there could be a galvanic issue with the shaft that has caused parts to corrode or error faster than they should.
Or maybe just bad luck.
My money would be on hitting something with that prop shaft…… Whether it was noticed at the time or not. (probably but maybe not as hitting something).
Anyway, this is only (academically informed) speculation!

ship fixer

I doubt she’s hit anything Prop. More like a unique defect caused by progressive degradation of components within the coupling. Given it is coated anyway it will be difficult to ascertain condition in the water (and for the remaining three couplings in service, in class) but this is taken on risk. Poor installation is also not probable as shipbuild and other repair providers have removed and installed hundreds of these on platforms in the past. As said, mean time between failure for this bit of kit is vanishingly small. It’s a bad luck even rather than a swiss cheese cock up.

Last edited 1 year ago by ship fixer
Supportive Bloke

What I’m amazed by is that, if as you say, the coupling was slipping and allowing the motors to free rotate under no load the torsional measurement of torque on the prop shaft didn’t pick up the no load condition?

A quick look over the stern might have been quite diagnostic too? Tiny amount of prop wash means little or no power in the water…….?

Strikes me as a failure of common sense?

ship fixer

The last thing you would expect – believe me – in that scenario is that a component of previous top reliability having failed in situ. Besides, a glance over the back end wouldn’t tell you much – the prop was possibly turning slowly anyway and only and the inertial of the coupling providing enough rotational momentum through the two parts of the coupling. If the shaft was turning quicker than the demanded lever the last thing on my mind would be the coupling moreover the myriad of pickoffs and algorithms within the quite complex propulsion management system. The final failure only possibly occurred when forward momentum took place on the affected propeller and pulled it free of the coupling. Like I say, mean time between failures on these couplings is vanishingly minute, as low as your car falling entirely in two whilst driving down the motorway. This is a freak, bad luck event and not a swiss cheese cock up.

Supportive Bloke

I accept what you say about the general reliability of the couplings without question.

I also agree it wouldn’t have taken much to slowly turn the rear part of the shaft only a tiny bit of residual interference fit.

The inner research scientist in me always questions the instrumentation first when I’m looking at an anomalous result. I suppose it is a mindset and training.

Commonwealth Loyalist

Well sorry to hear about that, rather amusing that POW would not even exist if it wasnt for the clever contract. But I don’t think the main fault lies with industry but the govt for not funding the defene forces anywhere near what is needed.

Salty Dog

It’s a broken coupling ! things break,


They do indeed. Now let’s get her docked and fixed asap


Its a shame the old King George V dry dock in Southampton is no longer operational. I am led to believe she would fit in there.


The dry dock isn’t the main problem in Southampton. The problem is the lack of a full ship repair yard and all that brings in terms of facilities.


Bravo Zulu, a very good write up, good reporting.
WRT dry dock & repair facilities: I’m currently reading “Under the Red Sea Sun” by USN CDR Edward Ellsberg–the story of his salvage & restoration of the [Italian] naval repair base in Massawa during WWII, to support critical repairs to RN cruisers in the Med (when it looked like Rommel might well capture Alexandria). Strongly recommend it for anyone with a historical interest in wartime salvage ops.


That doesn’t seem a good enough excuse but what about the advantages? Excellent rail connection and power grid. Looking for a Rolls Royce solution when you need a JCB. The docks are full of heavy lift gear and recently we had a repair ship.
Navy needs a mover and shaker to get this sorted.


Great comment. Yeah shame there is no need for ship repair and refurbishment in Southampton. Its very rare we see large ships in port. In fact they never repaired or bulit any ships in Southampton according to Goggle earth.


Vosper Thorneycroft shipyard on Itchen river Southhampton. The T42 HMS Gloucester was built there

Margaret Biwen

What happens to the crew whirl the repairs are undertaken

Andrew Deacon

They were in portacabins at Rosyth while HMS PoW was being built so little accommodation available there. Most will be back to Pompey or things like leave or training.


The repairs are for the propeller shaft area The rest of the ship is fine. Crew should stay on board for what is a short stay. But I imagine the senior officers will go on leave. Maybe the aircraft and aircrew return to home airfield


If it’s a short stay. If new shaft and prop parts are needed it could take a number of months to get them manufactured.


To construct such a facility in Pompey has been estimated to cost around £500M, funding the RN simply does not have.”
How much would it cost to recommission the King George V graving dock 20 miles’ sailing away at Southampton? On the face of it, seems obtuse to have a single compatible UK dry dock that’s c.700 miles from home port – and with weeks-long waits to pass under the bridges too.
(For wider UK fiscal perspective, NHS England will spend £500m every 32 hours in 2021/22, not including Covid-specific additional expenditure which is another £500m every 129 hours this financial year. Source: The King’s Fund.)


Have a look at the dock on Google Earth. It’s surrounded by other users of the dockyard. To make space to both built the workshop facilities needed to actually use the dry dock and secure the site would mean disrupting one of the biggest and most important commercial ports in the U.K. That’s just not a sensible thing to do for a dock you only need for a few weeks every couple of years plus emergencies.


Clear open land for container parking surrounds the dock, so not much disruption on other activities apart from a reduction of their space:
King George V Graving Dock – Google Maps
Zoom out and see how big the port is; absolute no need to take up anything like a significant portion of this vast area, which has multiple access points:
King George V Graving Dock – Google Maps
And the QE Class only needs a dock two-thirds that length. You could build facilities over it as well as around. As for security, container ports are already well protected (no-one can just stroll in) and the dock is well-within the boundary. So I don’t believe it’s insoluble.
Even if Southampton needed a small reduction in capacity, I’m sure it could be found by ABP elsewhere in the UK:
Associated British Ports – Wikipedia


You could do it but I doubt ABP would let you with giving them a lot of money. They just don’t need the hassle/any disruption of their main business.
The other question is why do it. If you want to keep the dock available for carriers where do you find the workers just for the few weeks every so often when a carrier needs service.
Rosyth has a number of docks so keeping the biggest open for the carriers still leaves others on site doing RN repair/refit/scrapping work plus the ship building operation. This gives the yard all the support and facilities needed to support the carriers.
In summary ship repair is far more than having a big dry dock.


The KGV dock in Southampton was for many years leased by A&P ship repairers who are still in business with their other UK docks
Of course once the owners sold the site off the dock caisson was removed and just used as a low value cargo wharf


What Ho, What a struggle to commute 20 miles to work.The real reason is because they have decreed there will be no more ship repair or ship building activity in the South of England. Full Stop.


Who, pray, are “they” and have you tried the M27 recently?

There is plenty of naval ship repair work in the South of England. The only thing that isn’t there is a QEC-sized dock. Other than dockings, ALL the QEC support work is done from Pompey – and is actually a struggle to man up. ALL the T45 work is done in Portsmouth (standfast the PIP, which I suspect will migrate south). ALL the T23 repair work is done in Devonport – as is ALL the LPD work.

Shipbuilding won’t be coming back to the South, because all the core build workforce have retired or gone elsewhere. That was a BAES decision, albeit endorsed by HMG because no-one had the nuts to end shipbuilding on the Clyde.

That leaves commercial ship repair and shipbuild. Lets take repair first. Other than things like coastal ferries, there is a vanishingly small amount of work out there. A&P struggle to support Falmouth, Hebburn and Teeside, Lairds get some Irish Sea Ferry work. H&W are trying to get a slice of a small pie. Beyond that I’m struggling to think of ANY viable ship repair yards in the UK.

Commercial build is a pipe dream.


Give me a break.


You are right of course. ABP are selling off 20 acres on the far West of the dock so they aren’t short of land.
Besides replacing shafts and propellors is relatively simple work and doesn’t need vaste workshops and gazzilions of riveters, sailmakers and welders.
Things come made off site this century.
Besides we need a new repair ship.
Failure to reactivate KGV dock is our typical British failure to invest and have a go.

The Ginge

Whilst I can see the points you make, the simple fact is as far as I can remember we never had this problem with the Invincible Class ships. In fact since 2000 you have to ask what has gone wrong with RN Naval Propulsion since we have now had the well documented T45 problems, the T23 problems since their upgrades with the latest being a dead ship at one point and now Carrier problems.
The reality is both QE & PoW have had numerous problems throughout their short lives. Secondly we were incredibly lucky that at the start of their careers QE was available as it will be rare that both will be available and in view of the limited number of F35B’s we will have it makes even more of an argument that we should have built 3 40,000t ships. With 1 in deep maintenance, 1 in light maintenance able to deploy if required with some notice and 1 active as they permanently rotate, rather than putting all our eggs in one available ship at a time. I suppose hindsight is a wonderful thing, but apart from 1 deployment by QE using American Marine Planes to make up the numbers it has not been an illustrious start to these ships lives. I always thought that PoW was an unlucky name anyway to start with.
I am sure all are doing their best, but the impression is given that these two spend an inordinate amount of time alongside shrouded in scaffolding.

Andrew Deacon

Social Media! That is problem now – it’s all in public gaze. Previously you had to rely on Navy News and whatever came out of the yards. Unless you had a very public problem like HMS Nottingham, most of the world is unaware.
As for more ships I do agree. That could mean 1 more would have LPH capability to replace HMS Ocean. Invincibles were too small and could carry a Commando and put ashore by helicopter but no way of landing the equipment.


Invincibles were bigger inside than their displacement showed. More volume than a 27,000 ton Hermes type.
It was the thing in post war period to cram a lot of people and capability into what would be seen now as small ships


The closest I can think of is Invincible swapping out an Oly on the way to the Falklands.

But things have always broken down.


Marine GT like the aviation engines they are derived from are ‘designed’ to be overhauled off the wing/out of engine room. It may have been its ‘hours’ were up and time for its major service but the circumstances meant no time to sit in port to do this


I said the closet thing. I know a bit about taking GT’s up uptakes.


“as far as I can remember we never had this problem with the Invincible Class ships”

No. We never had this problem. We had lots of other problems. Invincible herself had numerous Gearbox problems. Lusty had a major GB casualty when about to deploy, which resulted in months in dockyard hands.

“it will be rare that both will be available”.

Justify that statement. In your own time, go.

“the limited number of F35B’s we will have it makes even more of an argument that we should have built 3 40,000t ships”

We’re buying fewer aircraft, so that makes more sense to have more ships? Would never have got past the IAC – and would have cost more to build and more to operate.

Last edited 1 year ago by N-a-B
Andrew Deacon

Take a look at this previous article justifying size of the carriers
Are the Royal Navy’s aircraft carriers too big? | Navy Lookout.


Having been somewhat involved from the mid-90s on the carrier programme, I think I might just understand without that, thanks.


Are you Tom Bradby’s researcher then?


It’s nice for you to own up to it. 🙂

We still like you. 😉

ship fixer

Mean time between failures on SKF/Voith couplings: all T21, T42, T22, T23, T45 and foreign navies and commercial vessels, x 2 the x hours run. Vanishingly small attrition rate.


it will be rare that both will be available”.
Justify that statement. In your own time, go.

No you justify it. A decade from now one will be at sea and one will be in refit. You know it.


Which is hardly what I’d define as “rare that both will be available”.


Rubbish. 😉

Last edited 1 year ago by X
Defence thoughts

At what point does a ship in refit become unavailable until that refit is completed?


Depends on the scope of work. Which is why we have Fleet Time and none-Fleet time support periods.


But the RN never ever really operated the Invincibles on 3 for 1 basis. It was more 2(+1) for 1. The third ship was often alongside in bits (those bits in the other two hulls) and then eventually went for refit. It was very drawn out. So losing one of the hulls doesn’t matter really. We don’t operate escorts on that basis now. The days of a ship being relieved on station are long gone. And we don’t have enough ‘escorts’ for all the ‘stations’ now. Never mind the rapidly shifting international situation with the West as odd as it may sound becoming “isolated” in the worst case or just one of another power blocs at best.

Aviation ships are best built big. A lot of the big costs for a surface ship are systems not hull. And to use hackneyed phrase, air is free and steel is cheap. We ended up with big aviation ships mostly because Blair saw himself as President of Europe and saw himself sending European carrier battle groups about the globe with “British carriers” at their centre. I think it is a mistake that there weren’t CTOL ships. There are good arguments for VSTOL but it does cut us off for the USN carrier mainstream. Especially as HMG doesn’t want to invest in systems to support VSTOL. Would we not have been better off with E2x than the lucklustre and cheap Crowsnest? There is a lot of talk of drones. The USN has an active program with fullsize aircraft, we are playing about with oversized RC planes. It is all very well saying F35b is a super stealth aircraft but the bomb truck is only part of a complex machine. Would we not better off with say Rafale-M? Probably. If the balloon does go up the QE’s will be with the USN / USMC ARG’s carrying USMC Bravo’s freeing LHx deck and hangar space for Osprey.

Wearing the hindsight goggles we should have built a pair of 40k tonnes LHA’s to support what we did well in terms of ‘surface warfare’, ASW and (light) amphibious warfare. Two hulls to support the Fleet and not be the centre of the Fleet. We should have let the RAF have fast air in terms of operating Bravos. And we should have thrown money at Crowsnest to make it a world class system. A couple of cruises each year say one for the RM and one for ‘surface warfare’ all in the Atlantic or Med. All achievable.


Dont think the President of Europe thing really matched the existing and proposed EU members naval aviation
France had a nuclear CTOL carrier, Italy was upgrading its VTOL ship and the same with Spain.
If anything Blair wanted to be seen as the senior partner with US on a global arena not ‘herding cats’ with an EU navy


I think he wanted a bigger job than being PM of the UK. As for not matching the aviation that is one of the reasons why QE was given the green light. He watched Top Bun too many times. Like most politicians he knows nothing of military matters. Then again much the same can be said about a good number of our admirals and generals and air marshals…….. 🙂

William Pellas

The Ginge, I think you’re dead on it. To have legitimate carrier aviation, you need a minimum of three (3) hulls, not two. Of course if three 40,000 ton ships had been built, the spotlight would have shone even more brightly on the RN’s overall shortage of ships in the escort fleet. Absent a massive upgrade in spending and naval construction, it appears unlikely that the RN will exceed 24 vessels in terms of major surface combatants any time in the foreseeable future, and so one could reasonably ask how so few escorts would fare with 3 carriers to protect rather than two. Even so, if you’re going to be short all the way around, it would at least be better from a deployability standpoint to have three flattops rather than two. Here’s hoping that next time around, this or a similar course will be what the RN does.

Rose Compass

Never having served I had to look up the meaning of ‘threaders’ to determine that it’s forces slang for being angry or fed up. Apologies for my ignorance.

Rose Compass

Just for reference, mind:

These things happen, best that they happen early in a ship’s career.

ship fixer

Its a hydraulically locked sleeve coupling that has been used for decades by numerous maritime entities.


Threaders can also mean absolutely fecked. It depends on the context of when its being used.

ship fixer

‘Threaders’ in this cased means ‘pissed off’


Personally I think through have created an enormous circus for nothing. PR matters, especially when the newspapers are read by the pillicks who make the funding decisions at Westminster.

David McCullagh

As a marine engineer, I specialised in Propeller shafts, stern tubes and thrust bearings on commercial ships using CP Propellers. The SKF muff type coupling is a reliable method of connecting propeller shafts to propulsion prime mover. It is a simple tapered split sleeve, outside of which is a solid heavy steel tube which is forced axially by hydraulic pressure to close the inner sleeve to give a friction fit on each of the two shaft ends. This hydraulic pressure is provided by either a hydraulic power pack or a hand pump which looks like a grease gun! There are witness lines on the coupling to show if the coupling has been installed correctly. The whole unlocked coupling can be moved
axially along the shaft joint to allow seperate rotation of either the prime mover or the propeller shaft. If this coupling becomes unlocked when under way using only one propeller, this shaft will move aft and only stop when the propeller blades collide with
the rudder. Pretty extensive damage will occur.  Is it possible the coupling was disconnected to carry out tests on the prop motor ?


That conclusion sort of fits with the known issues with the GE integrated drive system.
Could it be like the F35B accident , a simple cause of human error?

ship fixer

Nope. Bad luck incident.

ship fixer

It wasn’t disconnected for any such trials

Drew murrY

She could be sailed straight into inchgreen drydock in greenock .with far easier access than Rosyth. 43 cdo are based across the clyde at faslane, and could provide a temp security until a permanent solution is put in place.


Inchgreen is just a big empty dry dock with negligible facilities or workforce. Why go there when you can go to Rosyth with its working shipyard facilities? Yes it’s a bit inconvenient to get in and out of but for a job that’s likely to take till we’ll into next year it’s not an issue.

ship fixer

Rosyth has ‘the’ dock where the platforms were assembled and facilities are permanently kept there (such as the vast overhead crane) and other dockside facilities to enable docking and a fast turnround. Much of the workforce which built this platform are available and HMS Caledonia is nearby to accommodate ship staff whilst repairs are taking place. And it sits within a secure semi-military site with a comprehensive and competent shipbuild safety environment already embodied in Babcock


I would think the crew ( except aviation)would remain on board if its only a week or 2. US navy base crew stay on board


I’ll be very surprised if this job only takes a week or two. If new shaft sections are needed it could be a very slow job.




Plus significant shaft and prop damage together with minor ruder damage. I don’t think this will be quick unless all the parts are in stock.

Doug McCrae

HMS Caledonia is due to close imminently


Its a training base .
latest reports to House of Commons give a 2026 closing date

Jack Jacksen

Bad decision to sail the carrier, when she wasn’t fit to be at sea. It looks like that decision caused very serious further damage. It seems it’s going to be a costly and long repair.


Why does a class of ship of this displacement, beam & draught not have 4 shafts/props One may liken it to Nelson & Rodney with their pair of oversized props.


Thats related to the power output able to be used by the propellers. Liners and such go for smoothness that 4 shafts gives – if they wanted the carriers a much higher top speed 4 shafts would have been necessary
This happened in WW2 when Illustrious class were built and had 3 main turbines and shafts ( like the earlier Ark Royal) but the last 2 , Implacable and Indefatigable were improved with a slightly higher top speed from more boilers and 4 turbines/shafts. The higher speed could have been achieved with larger diameter propellers on the existing 3 shaft design

Last edited 1 year ago by Duker
Iain Sanders

How EXACTLY did the coupling fail – metal fatigue in a component would surely be the only acceptable explanation. Otherwise, what? When were these last checked: was everything tightened-up, stresses equally distributed.. Was this due to a loose bolt or other fixture..
From the SKF website: ‘Coupling systems are critical components that connect vital applications such as propeller shafts, propellers and rudder assemblies. If couplings are off by just a fraction, they can be prone to premature wear and shortened life cycles. SKF coupling systems are designed to resist high torques to provide maximum strength – reducing downtime while keeping your operations running.’

Last edited 1 year ago by Iain Sanders

It’s unlikely much progress will be made on the investigation until the ship is in dry dock and the parts can be properly examined.

ship fixer

Likely the hydraulic lock failed due to a number of reasons – surface condition, angular deflection, seal breakdown or other component failure

Very Concerned

Need more than two carriers, need to build two more.

ship fixer

Yeah. There’s another £6Bn down the back of the sofa. And a spare 1500 matelots to man them



Defence thoughts

QE’s replacement might be more in number. You never know how things might go!

Jack Jacksen

If you go for electric propulsion, surely it would make more sense to go for ‘pods’ to power the ship. I know people criticise this and say it’s not applicable, but isn’t it easier to swap a new pod in, if you have a failure, rather than all this complication of shafts and couplings. Better to have something at sea that works, than sitting useless in a dry dock.

Prop chief

But if you loose the pod, you also loose steering!
Also, and I’m not 100% on this as pods are not my background, but when QEC was drawn up, pods of the power required didn’t exist.
Also, the GE Aim (motors) were proven tech in other warships at the time, so better corporate knowledge and simpler spares holdings.
Just a few thoughts, although I’m sure pods will prove their worth in many applications!


Pods were looked at during the design studies. There were question as to how well they would hold up to explosive shock.
Pods like all systems are not perfect. As a for instance the Australians had big issues with their assault ships pod drives a few years ago.


They were minor problems , such as you expect with a new ship

ship fixer

By the way – I was a Prop Chief once


“but isn’t it easier to swap a new pod in, if you have a failure, rather than all this complication of shafts and couplings”

If you define “easy” as manoeuvring a unit that weighs several hundred tonnes or so under a ship where cranes can’t plumb, and then offering it up to a bearing face/watertight seal, checking tolerances, potentially machining to fit, plus sorting out HV cabling etc etc, then maybe.

Most of us engineers wouldn’t describe that as “easy” or quick.


Taking off a very large propeller and withdrawing the shaft ‘under the ship’ cant be easy either. ( QEC propellers are said to be 33 tonne each) But they do it
I would imagine a pod is a modular repair basis


Imagine being the operative word.


Do try to keep up
‘Boskalis is to repair two Azipod engines on a Carnival Cruise Line ship using floating dry dock, a process requiring one of its vessels to be half-submerged.’
Floating dry dock , who would have guessed such new fangled things could be used for a 115,000 ton vessel

Last edited 1 year ago by Duker

keeping up , part II and Part III
“The latest design, the Azipod X, incorporates these improvements, with a view to a service interval of five years, and features bearings that can be taken apart and repaired from inside the pod while the ship is harbored normally.”

In June 2016, the QM2 docked for planned maintenance at the Blohm & Voss Shipyard in Hamburg, Germany. The maintenance included replacing the drive-end CARB bearing and the non-drive-end spherical roller thrust bearings on all four pods. “
These are 250 ton units

Last edited 1 year ago by Duker

You’ve never actually done any of this have you?

I’ve supervised shaft changes in a dock. It’s largely down to having the correct rigging and lifting points in place. Ditto change of props.

Bit of staging, couple of cherry pickers, can be done in a week.


So now it’s easy to do ….by people who know what they are doing of course.
And as I’ve found out , a complete amatuer, that modular is available as well.
It’s moot here as the Wales doesn’t have any


“Modular” if you’re prepared to have a unit (or two) that costs £10M plus each sitting round in a store next to a particular dock.

If you’re not prepared to fund that – or if you want it moved from the factory to wherever your dock is, it’ll be the equivalent of a trip to the stores for the Long Stand…….


Theres dozens of cruise ships that have these pods and theres even a mobile floating dock that can lift and repair some of the largest liners… even in Bermuda
Im sure you remember the days of the hammerhead cranes, when they had to lower very large weights into the floating hull during fit out.
Like I said when I ‘imagined’ certain things – because I dont have direct experience but understand those that do have amazing ingenuity- and easily found online these types of repair while in dry dock.


Indeed. Dozens of cruise ships do have pods – for very specific reasons which pertain to them. How many of those cruise ships do you think have spare pods sitting around for “modular” swap-out repairs as you and the OP suggested?

There’s a reason there’s a big mobile floating dock in Bermuda and the Caribbean. Could it possibly be that the area has no suitable existing infrastructure, is a very popular destination with cruise ships which are unfortunately prone to having propulsion casualties?

Not entirely sure what relevance your hammerhead crane has in this scenario. I assume you realise that such pods have to be offered up to the hull from below, because cranes can’t plumb their location? This tends to require KAMAGs or similar that can carry such a load, manoeuvre it to the correct position and then lift it.

Again – “modular” repairs as suggested would require spare pods lying around, waiting for something to go wrong. At £10+ a pop and well over 200 te, they’re expensive and very difficult to shift.

The internet does not equal knowledge. Off to the stores to pick up the Long Stand for you……

Last edited 1 year ago by N-a-B

Sorry to bang on about KGV dock but that shows how convenient it would be to have it working again, just 20 miles from Portsmouth. Maybe the top brass have been given the runaround. Thanks.

ship fixer

Feller – you can’t magically transform a commercial dock with no inherent military infrastructure into ‘the solution’. The dock plan has to match as does the profile. Docking a ship isn’t a piece of piss – I’ve done it several times.


It was leased by a ship repairer A&P ( connected to the then shipyard Austin and Pickersgill) until ABP sold the site.
I would say the time passed the loss of skilled staff, the dock gate and other pumping equipment means its no longer useable as a dry dock. The RN made the right choice in choosing a working shipyard at Rosyth


So now you are saying you dont need much specialised equipment. I think whatever you say there is a case for KGV Southampton that can be done if there is a Will.
Frankly I’m amazed it isnt even being considered.

Phillip Johnson

POW sailing with civilian workmen aboard………, where have I heard that before!

Seriously, let’s have some care for the poor sod that was convinced to sign off on the waiver paperwork for the ship to sail at all,
Said sod now occupies the position of scapegoat number ONE.
Two points

  1. A coupling failure is very, very unusual;
  2. Rudder damage? That suggests that the coupling broke and the shaft aft of the coupling slid back and the prop boss hit the rudder!!!! The electric motor may have over speeded if that was the case. The stern tube seal will also be in question. In each case we are talking about class specific components that weren’t expected to fail
Bob Young

QE wasn’t going to the Med and Diamond was not escorting her.



Bob Young

In the original article it stated HMS Diamond was QE escort and they were going to the Med…. they were not going to the Med. So unlikely DMND would go to the states.

Bob Young

“QNLZ was due to commence a 4-month deployment to the Baltic and Mediterranean with embarked F-35 jets. Instead, she will sail next week for the east coast of the US, most likely with her escorts HMS Defender, Diamond and Kent. She will perform some of the defence”

Mike B

The cost of a dry dock in Portsmouth would be offset by allowing foreign navies and commercial ships to use it.
Portsmouth also needs the investment in jobs.
The cost of towing or having tugs accompanying her to Scotland will cost millions.
The embarrassment of this incident due to PoW being alongside for weeks has no monitory value.
It should not have happened and something similar will happen again without the proper support in place.

Bob Young

It won’t cost millions to use tugs, we already use them every day.


True. As an aside the MoD(N) are constantly looking to reduce the number of harbour movements because of cost. That is why they built huge carriers to operate in a small harbour without bow and stern thrusters.


And what happens when a commercial ship is using this new ‘mega Portsmouth’ dry dock when the RN suddenly wants it ? Do they say you have got 12 hrs to get out , no matter that its 2 weeks left to complete your work ? The carriers are so big they need the full dock, not just a caisson separating it into 2 halves with the last half free
Other navys have their own docks for precisely the reason they have complete control


It would never be offset by commercial or other naval work.

That is precisely what Fleet Support Ltd was set up to do when the dockyard operation was privatised twenty years or so ago. Their biggest customer was Wightlink ferries (using 9 dock IIRC). Plus looking after the BAS boats.

No-one is going to put a dock of the size required in Portsmouth, largely because no-one wants to find out just what lies beneath C&D locks, not to mention 3 basin.

Here’s another thought. The USN has two carrier bases on the West Coast. See if you can guess how many have CVN-sized docks (it isn’t both). On the East coast, see if you can guess how many USN carrier bases have CVN-capable drydocks.

Last edited 1 year ago by N-a-B
John C

Should probably point out that in the last piece where I’d suggested she might have put to sea aware of there being an issue, I *was* joking. Another fine example of the adage “Can’t take a joke? Shouldn’t have joined.”

Bob Young

True.. but she probably did put to sea knowing the problem was there, just not the extent of it.. fair assessment in my view, although jokingly haha


There’s an unassuming agent opening a very large briefcase of Euros in a European dry dock right now. Hoping to jump the queue…


RN has a dock on standby at its Rosyth base exactly for this sort of scenario

Howard Brisland

Southampton has the dry dock required. It has been let go being used to export scrap metal! If a small percentage of the billions spent unnecessarily dredging Pompey was directed to upgrading and maintaining this strategic facility. Well, right on the door step.
I spent a lifetime sorting bigger problems on bigger ships than this. Political decisions taken by here today gone tomorrow corrupt….I shall stop now, just an old fart.

ship fixer

Yeah. Stop now. This generation will sort this problem out. You do understand that the defence infrastructure and warship repair facilities being in PNB kinda influenced the ‘billions (erm it wasn’t) spent on dredging Pompey’ decision. The Royal Navy is based in Pompey, has been for centuries and will continue to be for the foreseeable. Southampton doesn’t have anything viable for military ship repair on that scale.


Some of his details may have been off the mark , but the thrust of it is correct.
( the Southampton dock was never owned by military)

Due to Treasury’s capital charges every year on every piece of military hardware or base facility they are all ways selling off sites – to be covered by ‘pseudo leases’ from private companies- or ‘taking out of service’ otherwise useful military equipment.


We aren’t finished with this KGV Dock business. Its a set up. Its not being used for anything useful but we’d better hurry before they fill it with concrete and use it to build a block of holiday flats.


Definitely not holiday flats as it’s smack in the middle of a dockyard, but extra container parking wouldn’t shock me. I did read somewhere about the dock or surrounding area being listed, not sure if that’s true or what difference it would make.


The pumphouse is. Quite comical that this was ‘chosen’

Howard Brisland

I have fixed ships in Southampton,Pompey, Newport News, Virginia, Rio, Gib, Rosyth, Belfast, Cardiff, Bremerhaven to name a few so am well aware of the capability or, what’s remaining in this country all be it I am twenty years out of date.

We would flood the fwd tanks on tankers to raise the stern out of the water. Build a cradle and remove rudders, props and pull tailshafts as there was no available dry dock. But as I said I am just an old fart!

No wish to start a comment battle but I really do know a little bit about marine engineering and the facilities required.


I’m an old fart too. Doesn’t mean we don’t understand Strategy and Grand Designs. I agree with you, it has been let go probably because someone somewhere said we aren’t interested in ship repair, ship building and doing things for ourselves.


No Dry Dock in Pompey but one (KGV dock) down the road in Southampton with direct access to a good depth of water. I’ve yet to hear a credible excuse as to why that can’t be requisitioned if necessary and put back into service. Has anyone done any serious homework on this? We know it needs a new gate and removal of the Grade 2 listed pump house.

It was paid for with taxpayers money. If you need workshops and gantries etc, that would be possible to fix.

Is this down to security and because the football team isn’t Pompey? If we were at war, we’d do it wouldn’t we?


It’s because we don’t actually need it.

Interestingly all the people wibbling about KGV seem to be doing so on the basis that somehow access to Rosyth is restricted. Not a one of them has thus far looked at the whether depth of water available in KGV itself is restricted…….


Wiki says RMS Queen Mary 1934 draws 38’9” in old money (11.8m) vs HMS Queen Elizabeth drawing 36.0′ (11.0 m). (Looks like ABP owe the UK a new dock gate at least for letting KGV gate fall into disrepair through neglect and a reminder that the USA wont allow its key docks be foreign owned as they see them as vital national assets. Why should we?) Anyway this is stuff and nonsense having a dry dock on the RN’s doorstep and finding every excuse why its all too difficult to have it on standby for the carriers.


Wiki is rarely a good source of information. Just because it suggests that QM drew more than PWLS does not mean she could get in at all states of the tide. Which appears to be the only reason people are wibbling about a defunct dock – as opposed to the funded and available solution.

I’d start with cill depth of water below chart datum. Then I’d start adding up things like dock block depth, required clearance over the cill and see what that gave me in terms of state of the tide required.

Then I’d probably start asking what impact an explosive safety zone (necessary because the ship may be bombed up) might have on the operation of Southampton Port, let alone the glib statements from some about space “only being required for containers”. Which is the principal determinant of how much cargo a container port can handle.

Compensating ABP for those sort of constraints is likely to require a shedload of money to solve a “problem” that exists only in some fevered minds.

Last edited 1 year ago by N-a-B

I think a big part of the enthusiasm for KGV comes from the anti Scottish sentiment that is quite prevalent here.


I think the Navy have just had a wake up call and it would be surprising in the circumstances if they didnt look at KGV as a worthwhile option. We’ll see.


It was paid for with taxpayers money. “

it was built and owned by Southern Railway, privately owned at the time who owned the surrounding port area
Its purpose was drydocking for the large Atlantic liners who used Southampton at the time


It was subsidized by the Government as were RMS Queen Mary and RMS Queen Elizabeth.


Before we go any further, RN looking to start designing New Type 83, so it way be time for the hindsight engineers to apply for work & save the RN time & money !


I am thinking they should make it inflatable. 🙂

comment image

Last edited 1 year ago by X

I am now waiting for Type 26 to break…. Maybe one of those heavier Australian ones will even tip in a tempest due to heavy top weight.
It will be called the Coral Sea Incident!


Can be guaranteed to happen. Its what new ship classes do. The USN Burkes have had a range of issues
The RAN ships increase in weight is still within design margins…one of the reasons modern frigates/destroyers are so much beamier is the higher amount of top weight and lesser bottom weight ( no boilers and steam turbines- condensers)


As a frenchman, I express all my support to RN, sailors and Britain. Building and operating carriers is not easy. These disappointments are not uncommon with new ships. No doubt PW will have a great service.

William Pellas

The RN really needs three (3) QE’s in order to reliably have two able to deploy at all times, but that’s not going to happen. Perhaps if the UK is still building carriers when the time comes to retire the QE’s, there will be three flattops next time around.

Meanwhile this is now the second major mechanical breakdown for the Prince of Wales in the few short years since its completion. Very embarrassing, but of more concern is the possibility of shoddy workmanship. This is a distinctly disturbing trend when one considers the major problems with the T45’s propulsion systems. The UK is paying far too much money for its ships for them to be pulling up lame as much as they are.

Last edited 1 year ago by William Pellas

PWLS is certainly an unlucky ship thus far. However, the FER casualty was not “shoddy workmanship”, it was actually a consequence of a detailed design issue made nearly fifteen years ago.

The cause of the shaft casualty remains to be determined, but it suggests an unprecedented component failure rather than anything done in build. Particularly given that PWLS had spend nigh-on two months continuously at sea in late spring.

You probably want to see how many sea days the T45s – and indeed the rest of the fleet = are clocking up these days, before suggesting there’s any sort of endemic problem.


One carrier has broken down and the other one has not been fully fitted out. We don’t have a dry dock we can access at any time, but only when the tide is right, so repairs must be delayed.

With the SNP still rampant it seems to me the £500 million needs to be spend in the south to cure the tidal issue, provide a second dry dock and to avoid potential political crises if the SNP gets even more difficult.

Robert Harvey Barnes

KHM Portsmouth’s website stated that Seatec divers had been working on her 24 hours a day, 7 days a week for the past 3 or 4 weeks.

And that POW will be sailing this evening at 18:00, OSB> the NAB>??, plus 2 tugs.

Last edited 1 year ago by Robert Harvey Barnes
J Jacks

Which carrier has not been fully fitted out? I understood both can operate fixed and rotary wing aircraft and each can take over the role of the other.


Oh no, that’s so embarrassing, sailing to Scotland accompanied by a tug!

Graham Carroll

I notice that 3 months on there is still no clear news on how this coupling failed . If it was indeed an SKF muff coupling these are extremely robust and difficult to conceive of one failing . However as. a marine engineer I have been trying to imagine what could cause one to fail and I arrive at 3 alternatives . 1. Incorrect assembly, 2 Catastrophic failure of the outer sleeve due to material defect , 3 Incorrectly dimensioned shaft or inner sleeve of the coupling resulting in inadequate interference fit when assembled . Surely those in charge know by now which it was, so why the secrecy?