Preference for using the rear pantograph over the leading pantograph

[DJ_K666]

Moderator note - split from:

APT-P intermediate vehicle question.

I only ever saw an APT-P on the mainline once and that was at Crewe in the mid 80s. I was a bit put out by not being allowed to “cab it”. Anyway, one thing I’ve always wondered was were the passengers able to walk through the intermediate vehicles with the pantographs? This picture shows the...

www.railforums.co.uk

And by not allowing a 25kV bus cable to run the length of the train you had to put the power cars in the centre as both needed power, naturally.
Having a power car at each end and each one having it's own pantograph was ruled out due to standing waves being generating by the leading pantograph at high speed, which affect the wire contact of the rear pantograph.
Other high speed trains like the TGV have a power bus and so can have a power car at each end with only one of them with it's pantograph raised.

That seems to be how Pendolinos operate. It used to be the leading pan raised but nowadays it's the rear one.

 

[norbitonflyer]

That seems to be how Pendolinos operate. It used to be the leading pan raised but nowadays it's the rear one.

That seems to be standard on any unit with two pans. The idea is that should the panto bring the knitting down the other panto will be clear of the problem rather than risk getting entangled in it as it comes down.

 

[SuspectUsual]

That seems to be standard on any unit with two pans. The idea is that should the panto bring the knitting down the other panto will be clear of the problem rather than risk getting entangled in it as it comes down.

Veering off topic here, but it seems to be a lot less clear cut these days. Certainly with LNER, I’ve seen plenty operating with the front pan up and the rear one down

 

[43096]

That seems to be standard on any unit with two pans. The idea is that should the panto bring the knitting down the other panto will be clear of the problem rather than risk getting entangled in it as it comes down.

It's a nice theory, but reality is - especially in the UK - that you just stop in a dead section with knitting wrapped around the train, job stopped, passengers stuck on board for 4 hours with no aircon and the TOC promises that "lessons will be learned". Which they never are.

 

[185]

Back Pan is considered good practice. An extra few seconds for driver to spot something, hit the whoopsy button and pan down before ripping the knitting down. Known a few incidents where those extra 2 seconds have been crucial.

 

[Bald Rick]

Back Pan is considered good practice. An extra few seconds for driver to spot something, hit the whoopsy button and pan down before ripping the knitting down. Known a few incidents where those extra 2 seconds have been crucial.

It’s that, and (as others have said) if the pan at the front gets whacked, it can cause damage to the rear pan which will disable the train. If the back pan is used, the front pan is unlikely to be damaged and there is a much better chance of the train being able to continue.

 

[Paul AC]

It’s that, and (as others have said) if the pan at the front gets whacked, it can cause damage to the rear pan which will disable the train. If the back pan is used, the front pan is unlikely to be damaged and there is a much better chance of the train being able to continue.

However Hitachi's default is for 'leading pan up', thus throwing away years of operating experience.

 

[norbitonflyer]

However Hitachi's default is for 'leading pan up', thus throwing away years of operating experience.

Could this be because the rear pan's contact with the wire is more affected by turbulence from the train's passing? Is this more of an issue with IEPs than Pendolinos?

 

[Narrowgauge725]

When I asked by an LNER driver (Newcastle based) why they used the the rear one, certainly the norm going through Berwick, he states that it was because if the front is ripped off it is likely to cause far more damage to the train than if the rear one gets ripped off. Also if the front one is ripped off it may well take the rear one off too.

 

[800301]

Could this be because the rear pan's contact with the wire is more affected by turbulence from the train's passing? Is this more of an issue with IEPs than Pendolinos?

No, it makes absolutely no difference as to what Pan is raised on an 800, in a 10 car formation the front and rear most pans are raised,

GWR run on the front pan as per the 1 in 3 rule which would allow you to coast to the next available location to inspect further,

Pantographs are commonly isolated on 80X’s for various reasons so it’s not uncommon to see one running on the ‘wrong’ Pan

Sometimes drivers forget to swap the pans over

I was talking to a GBRf driver who said when they were testing the 805/7’s they had to run on the front pan but if an avanti driver was driving it would have to be on the rear pan.

I’d personally like to see some evidence of it actually making a difference in an incident as to what pan is raised

 

[Bald Rick]

I’d personally like to see some evidence of it actually making a difference in an incident as to what pan is raised

Well, not public, but theres plenty of Incident Learning Reports from OLE damage on the WCML from over a decade ago which recommended running rear pan up. This was because the front pan had been damaged, ripped off, tunbled down the train and taken out the back one.

 

[endofthetunnel]

Again it’s not public (and there’s no need for it to be, or indeed for this forum to be better at making the decision than the train operators) but anecdotally I’m aware of/been involved in numerous incidents where the front pan being raised would have had vastly different consequences to what actually happened using the rear pan. In fact so many don’t become public because a train doesn’t bring he wires down if the driver has the time to pan down before the obstruction, so there’s no incident really to discuss!

 

[800001]

Veering off topic here, but it seems to be a lot less clear cut these days. Certainly with LNER, I’ve seen plenty operating with the front pan up and the rear one down

If it's the front up on a 5 or a 9 it means the other pantograph is defective.
LNER units in a 5 or 9 by default should be the rear pan.

 

[Crithylum]

Another thing I have noticed is that the 345s usually run with both pantographs up, not just one.

 

[stuving]

Another thing I have noticed is that the 345s usually run with both pantographs up, not just one.

They have to, as they are built as two independent half-trains with no power connection between them.

 

[D365]

Another thing I have noticed is that the 345s usually run with both pantographs up, not just one.

They have to, as they are built as two independent half-trains with no power connection between them.

Correct and the same applies to Siemens units of six or more cars.