Braking issue on Caledonian Sleeper causes train to "run away" at Edinburgh

Bald Rick

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If I'm reading the report correctly when the locomotive went through the neutral section, the pan dropped and the rheostatic brake was longer functional. What should happen normally in this situation?
The friction brakes on the loco take over, which is what happened. However they are not designed to retard 500t of train. The laws of physics took over, they got very hot, and ‘brake fade’ resulted, further reducing their effectiveness.
 
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hexagon789

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I can't speak for the original brakes on a 73 but a while back I had a nosey inside a Caledonian 73/9 in Craigentinny and what I saw was a joystick type brake controller, similar to that of a 92!
Sounds like it's been altered to something like the European PBL90 system.
 

O L Leigh

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If I'm reading the report correctly when the locomotive went through the neutral section, the pan dropped and the rheostatic brake was longer functional. What should happen normally in this situation?
You mean apart from the pan not normally dropping?

My reading of the report was that the problem was more to do with the VCB not closing which lead to a fault state on the loco that lead to the pan automatically dropping. I don't know these locos so I'm unsure if there's a quick simple remedy, but I've driven EMUs of various vintages. If the VCB failed to close after a neutral section you could close it from the cab by pressing the Pan Up button, although on newer units the TCMS would take care of this for you.

As I say, I don't know what Cl92s are like so I don't know what cab indications the driver would have received. However, it would appear that this wasn't noticed by the driver who was already busy trying to slow the train down. I'm not even sure that he was fully aware he was already on friction or that he had no control over the train brakes until things had already got out of hand.
 

hexagon789

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If the rheo brake hadn't dropped out would that have been sufficient to have controlled the trains speed or was the severity of gradient and change in speed required such that at least some braking effort from the coaches would've been needed to control speed?
 

Dave W

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I don't know what the actual position is, but the report did make a couple of references to the effectiveness of the rheostatic brake.

On a related note, it also referred to the fact 92s don't return power to the grid. Would this have any bearing on braking performance, or was it simply to differentiate from modern EMUs which do?
 

O L Leigh

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If the rheo brake hadn't dropped out would that have been sufficient to have controlled the trains speed or was the severity of gradient and change in speed required such that at least some braking effort from the coaches would've been needed to control speed?
Well I touched on this a little earlier. My reading is that it would have depended on the limit of adhesion. Clearly the rheo brake is more effective than the friction brake, but you're still only braking through the same 12 wheels. Plus it was raining at Waverley when it arrived.
 

HSTEd

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Correct. But it's a system that is not replicated on the Cl92. To be clear, I'm not suggesting that a loco cannot have an EP brake, but rather that to have an EP brake the loco would require a fairly extensive electrical refit.
Really the railway needs to deploy ECP braking in place of the traditional air brake system in this case.
This accident occured because a desire not to spend money, and not move on from a supposed "golden age" technology.
 

Llama

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Hard to tell without recreating the situation, or someone with full knowledge of class 92 locos. The rheo brake would be operating outside of its design spec so even if the VCB hadn't failed to close after the neutral section there might be some protection system on the rheo which might've kicked in after it operating at full capacity for so long.
 

Bletchleyite

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Well I touched on this a little earlier. My reading is that it would have depended on the limit of adhesion. Clearly the rheo brake is more effective than the friction brake, but you're still only braking through the same 12 wheels. Plus it was raining at Waverley when it arrived.
Presumably if the traction motors are capable of accelerating the train, they are also capable of decelerating it at the same rate?
 

hexagon789

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On a related note, it also referred to the fact 92s don't return power to the grid. Would this have any bearing on braking performance, or was it simply to differentiate from modern EMUs which do?
Don't think it would as it would still be using the traction motors to brake so the braking performance should be the same I'd think with the only difference being that with rheostatic the energy is dispersed as heat through grids on the roof rather than part returned to the OLE, the problem is more with the rheo dropping out and the reversion to friction braking with thread brakes, disc brakes wouldn't be as susceptible to fading when hot.
 

hexagon789

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Well I touched on this a little earlier. My reading is that it would have depended on the limit of adhesion. Clearly the rheo brake is more effective than the friction brake, but you're still only braking through the same 12 wheels. Plus it was raining at Waverley when it arrived.
And presumably on 92s WSP activity reverts braking to friction only so the same problem might have persisted in that case.
 

O L Leigh

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Really the railway needs to deploy ECP braking in place of the traditional air brake system in this case.
This accident occured because a desire not to spend money, and not move on from a supposed "golden age" technology.
You did read the RAIB report, didn't you? That outlines the causes of the incident perfectly well.
 

HSTEd

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You did read the RAIB report, didn't you? That outlines the causes of the incident perfectly well.
The cause of the incident is that we are still using obsolete air brakes where an isolating valve can be closed without being easily detectable?

An ECP brake would have allowed the locomotive to detect a low reservoir air pressure at the back of the train, and if reservoir air pressure at the end of the train had remained high, then the ECP system would have caused the vehicles at the end of the train to brake even if no air pressure was available to refill the reservoirs afterwards.
 

43096

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Really the railway needs to deploy ECP braking in place of the traditional air brake system in this case.
This accident occured because a desire not to spend money, and not move on from a supposed "golden age" technology.
Read the report before spouting such nonsense. The incident wouldn’t have happened had there still been conventional couplers, brake pipes and robust isolating cocks away from where they can get knocked easily. The two pipe air brake system is inherently safe and reliable: it’s the badly thought out design on the sleepers that is the cause.
 

O L Leigh

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The cause of the incident is that we are still using obsolete air brakes where an isolating valve can be closed without being easily detectable?
Nope. There's nothing obsolete about the two-pipe system. The problem is that the Mk5s have a specific issue with the BPICs used, something that a minor redesign and a tightening up of coupling procedures would fix. That a brand new train has an issue of this sort does not undermine the technology.
 

hexagon789

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I wondered about WSP also and scanned the report for an mention of it, but as there was none I decided that it must have had no bearing. Also, do Cl92s even have WSP and how does it operate?
Given the similar age to Class 90s I assumed that they had WSP for motoring and braking and that they would operate in a similar manner but like yourself I have no idea of the specifics.
 

HSTEd

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Read the report before spouting such nonsense. The incident wouldn’t have happened had there still been conventional couplers, brake pipes and robust isolating cocks away from where they can get knocked easily. The two pipe air brake system is inherently safe and reliable: it’s the badly thought out design on the sleepers that is the cause.
If it's inherently safe and reliable how was closing a single valve able to so completely defeat the system with no apparent way for the train crew to tell this?

The placement of the valve was a problem, but the existance of a single valve that can potentially kill hundreds with very little that can be done to detect something wrong is something of a glaring safety issue.
 

Bletchleyite

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The placement of the valve was a problem, but the existance of a single valve that can potentially kill hundreds with very little that can be done to detect something wrong is something of a glaring safety issue.
Not least because it could be flipped maliciously?

There should not be a "crash this train" lever. It appears there effectively is.
 

37057

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The cause of the incident is that we are still using obsolete air brakes where an isolating valve can be closed without being easily detectable?
EP Brakes can have their issues too... Water ingress and shorting of connectors :)
 

HSTEd

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EP Brakes can have their issues too... Water ingress and shorting of connectors :)
ECP brakes are not EP brakes.

ECP brakes would detect a shorting of connections because suddenly the back of the train would no longer appear on the driver's desk display.
"Apparently the sleeper is running light engine tonight....."

ECP Brakes have two way communicaton down the length of the train.
So you can read status updates from every vehicle in the formation if you want.

The existing standard can even be used to control locomotives elsewhere in the formation, all over the same pair of wires (plus a power wire obviously)
 

43096

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If it's inherently safe and reliable how was closing a single valve able to so completely defeat the system with no apparent way for the train crew to tell this?

The placement of the valve was a problem, but the existance of a single valve that can potentially kill hundreds with very little that can be done to detect something wrong is something of a glaring safety issue.
Glaring? It’s been a fundamentally safe braking system for well over 100 years.

I’d suggest your response is somewhat hysterical.
 

hexagon789

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There should not be a "crash this train" lever. It appears there effectively is
The report notes that had the driver fully applied the train brakes before leaving the cab to assist the shunter with the ETS jumper then the train could not have moved with the BPIC closed as a full service brake application would've been maintained in the coaches.
 

HSTEd

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Glaring? It’s been a fundamentally safe braking system for well over 100 years.
So there has never been an accident or near miss accident in the history of a Westinghouse air brake?

I can think of at least one beyond this one from personal memory.

(Class 66 runaway at East Didsbury, when the hauled locootive was unable to tell the leading locomotive that it had no air pressure because a valve was set improperly)

EDIT:

That is a single piped incident, but the fact remains that a twin piped train would not applybrakes if an isolating valve in the non-reservoir pipe is closed. And there is no simple way to determine if this is the case without physically inspecting every isolating valve in the train.
This is a serious safety flaw.

I’d suggest your response is somewhat hysterical.
We nearly had hundreds of dead.
We could have been discussing a Class 92 led sleeper slamming into a morning commuter train full of hundreds of people.

It was only luck that the signaller was able to avert disaster.
 
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Taunton

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Not least because it could be flipped maliciously?

There should not be a "crash this train" lever. It appears there effectively is.
Was anyone concerned that the initial design described was to have the brake cock inside the vehicle, in a (presumably lockable) cupboard, where potentially anyone able to open the cupboard door could disable the train brakes. Whoever was doing the design?

Para 98 : In April 2016, the design intent was for the coaches to use a fully automatic coupler, which would avoid the need for operational staff to access the track during coupling and uncoupling. The BPIC was to be located in a cupboard in the end vestibules, so that the shunter could operate it from on board the train.
 

Bletchleyite

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Was anyone concerned that the initial design described was to have the brake cock inside the vehicle, in a (presumably lockable) cupboard, where potentially anyone able to open the cupboard door could disable the train brakes. Whoever was doing the design?
Given how often I see door control panels left open, I'm quite pleased they didn't do that (I know you can't do anything with them without keying in). Is it the norm on UIC coaches? I know you have the handbrake wheel accessible, and there's normally a cable through the gangway you could unplug (the loco->driving trailer remote control I think?). Though fiddling with either of those would result in the train stopping, not being unable to stop.
 

nickswift99

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It’s a super report, and a classic example of the ‘Swiss cheese’ model:

* late changes to design and function of coupling / connection systems
* BPIC not designed to correct standard (as a result of above)
* BPIC positioned in a place where it could be operated inadvertently
* Procedure for timing of brake continuity test had the potential for a different interpretation to the intention of the procedure relating to the coupling / connection procedure for this stock
* VCB opened and did not close, preventing use of Rheo brake
* Train manager didn’t have a functioning radio with him for communication with driver

It is likely that if any of these had been different, the incident would not have happened (or the train would have been brought to a stand at Waverley)

Fortunately, a couple of the swiss cheese holes were not aligned:

* the train had a route set through Slateford / Haymarket to Waverley, ie no conflicting movements set against it
* the driver had the presence of mind not to press the GSMR REC button
* the driver was able to contact the signaller, and the signaller was able to action the setting of a route through Waverley in short order
* the train manager was sufficiently aware of a problem, and pressed the passenger alarm button in the train (albeit it took two attempts).

Had one or more of these been ‘aligned’, then the consequences could have been rather worse.

A lucky escape, but a very unlucky chain of events.
The report appears to state that the first passenger alarm was effective but that the 10s delay in brake application didn't provide confidence to the Train Manager that it had worked so he used a second alarm. This is another design failing - the alarm should have provided some positive indication to the user that it had been effective.

I'm sure there's a reason for the time delay but it's not immediately obvious to me why that would be.
 

Tim_UK

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So I did understand it correctly. Presumably now they'll require a brake continuity test to be the last thing performed before moving and for one to be performed again if any alterations are made to the ETS jumpers.
One of the recommendations already mentioned.

And they also now using the Glasgow loco to split the trains, which makes the order simpler. You only need to go between the Edinburgh Loco and the Coaches once (I think)

It's quite concerning that the train brake system could be defeated so easily after a such a small action accidentally caused the BPIC to be closedm
There is mention in the report that they will change the valve to one with a bigger vent - this should make it more obivous in the cab that there is a problem.

(The compressor could keep up with the vent leak)

I wondered if the vent could be fitted with a whistle - so it goes with a bit more whoosh when opened. So you hear it.
 

TimboM

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The report appears to state that the first passenger alarm was effective but that the 10s delay in brake application didn't provide confidence to the Train Manager that it had worked so he used a second alarm. This is another design failing - the alarm should have provided some positive indication to the user that it had been effective.

I'm sure there's a reason for the time delay but it's not immediately obvious to me why that would be.
It's explained in the report, para 29:

An emergency brake application can also be initiated by operating the passenger alarm buttons in the coaches, although this is delayed by ten seconds to allow the driver the opportunity to override it. This override function is provided so that the train is not brought to a stand in a hazardous location, such as within a tunnel or on a viaduct.
It also mitigates against the use of the passenger alarm by less scrupulous passengers who have been known to activate the alarm on the approach to Euston (or or other terminus) to halt the train and tip a delay over the Delay Repay threshold...!
 

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