You are all wrong. They used to always run with the front pantograph raised until around four years ago when during a very cold winter spell it was found that ice was being struck by this front pan as the train passed through tunnels etc. The ice was then damaging the roofs of the following coaches and even smashing windows. It was decided then to minimise risk to run with the rear pantograph raised as any ice would hopefully only hit one or two following coaches. There was an article all about the switch in RAIL magazine at the time.
RAIL magazine has an alarming penchant for making any old rubbish up as they go along.
I was told by an Alstom operative that the main reason for the change was simply carbon wear and it's purely down to the knuckle direction - knuckle forward in the direction of travel maintains a more consistent contact force with the OLE and cuts down on carbon wear. Knuckle back is that little bit less efficient and wear increases. That's basic BR/BW High Speed pantograph behaviour that has been known about since the development work was undertaken.
It made sense to use the rear pantograph rather than swap the pantograph orientation on both vehicles as it was hoped having the rear pantograph in use would allow drivers to spot minor OLE damage, typically debris in the catenary or even dislodged droppers, and they could drop the rear pantograph. It was undoubtedly cheaper and easier too, given the pans on a Pendo have a counter-tilt electric mechanism.
It's slightly unrealistic, at the very extent of their field of vision, it buys them maybe five or ten seconds at most when doing 125mph (and they see significant debris in the catenary). Drivers will never be able to react in time for dislodged droppers or minor debirs at typical line speeds, but around stations and areas of complex pointwork where the catenary is perhaps more likely to be lightly damaged, it gives them a little more time to act.
Ice deflected from the catenary causing damage to the stock is pretty ridiculous, even for RAIL magazine. It's a known quantity on every route and isn't something which particularly affected the old LHCS on the WCML, or indeed, the IC225 sets on the ECML. Windows do get damaged in the winter, particularly when it's snowy and ice forms in tunnels, on parts of the OLE and impacts vehicles doing 125mph, but the ice being dislodged from the catenary itself does little or no damage to the stock.
Alstom's own staff think the Pendolino's propensity for broken windows in winter is down to their aerodynamics which tends to create more turbulence under and around the stock, allowing ice coated ballast to the picked up and thrown around. The tilt mechanism may also add small amounts of twisting force into the coach which weakens the bonded windows and combined with cold weather making them slightly more brittle, makes them more likely to break when hit by ballast during snowy/icy conditions.
