Am i right in thinking the tilt is only for passenger comfort, it's not like a 805 will topple over at the 390 speed
Tilt & speed supervision is mainly for passenger comfort. However. the class 390 & 221 were designed to tilt with calculated tip points & a suitable wheel profile. It has been mentioned that when TASS fails, the 390 or 221 does not fly off the track. This may be true in an instant, but failure of TASS initiates an emergency brake application to bring the speed of the train down to below that of the PS speed at that location. Running with TASS isolated or temporarily defective will result in horrendous ride quality approaching EPS speeds. The question about 80x tipping over on the WCML is answered with a yes. TASS strictly monitors the speed profile to which the driver must conform, including the braking curves. On the WCML the abundance of EPS running at 125 MPH means that there are a few key locations where a drastic speed change is observed, other than at junctions. Thus a class 390 with TASS can happily charge along the WCML at 125 MPH for long stretches. In broad brush stroke terms TASS will " allow" just a 2-3 MPH overspeed before it expresses to the driver its displeasure. If the braking curve is in danger of not being met, an emergency brake application will occur. The class 80x has had to be shoe horned into this method of operation with the MU speed profiles offered as a "fix" to fit in the EPS timings. However, as has been highlighted the WCML 80x series has no speed supervision system. It has no DAS system either. All it does have is a speed limiter on the train Management system, which is set like a cruise control. A whole breed of 390 driver has been taught to accelerate carefully & brake carefully only to be now told that the new trains are to be accelerated hard & have superior brakes. The number of speed increases & decreases with trying to introduce MU speeds is greater since there is a stepped up & down approach. Now back to the tipping over... It would appear that once the MU speed profiles were set & £16m spent on putting the boards up, it became clear that there were indeed locations where a class 80x mistakenly operating at EPS plus the 2 - 3 mph would catastrophically derail owing to its different length/weight/wheel profile/etc. At the very least the risk of significant injuries to persons on board is high during predicted overspeed events. Thus we are now in the situation where the mitigation of such risk is to limit the Avanti 80x fleets to 110MPH & monitor the speed adherence of every single one to build up a bigger picture of the risk. It has been mentioned why not fit the WCML 80x fleet with a TASS? Its all down to money. Balises for 805 APCO have not even been installed. Engine pre heat is done either manually or via GPS fix, which is not always functional (to which the number of door release issues testifies). Whilst the current 805 / 807 fleet monitoring is taking place it is hard to say what the eventual decisions will be. What I can say is that the current 805/807 monitoring is producing some data of concern.
But lower maximum speeds apply when TASS is isolated and drivers are expected to know that already. The issue is 2 new classes of train that are expected to use a newly implemented speed profile that will be introduced in phases. It really is a recipe for mistakes to be made.
If you’re introducing a new train on a line fitted with a safety system, it does seem odd to not also fit that system. We don’t know exactly what they’ve asked Avanti to implement, could be they want TASS to control speeds down to a lower range than it currently does on the 390s.
Avanti have been asked to implement a review of every 805/807 journey in relation to speed profile adherence. This data is then likely to be used to determine a way forward, or backward, as appropriate. I would think that until absolute adherence to the currently imposed restrictions is presented to ORR then the MU boards will remain covered up.
If I remember correctly, TASS already uses eurobalises. Could a software modification to the 805s and 807s allow them to use the existing speed supervision using their existing ETCS equipment?
A lot depends on money. 807s were not ordered with a donkey engine to save money. 807s & 805s have no functioning Driver Advisory System. Re writing the software is going to cost. GPS rather than balises is used for engine pre heat & door release information to save money. Since the 805/807 has no in cab signaling, everything relies on a driver adhering to new extensive speed step up & step down profiles without the back up guidance of speed supervision with some areas presenting a significant tip over risk should it all go wrong.
Hitachi will of built what they were specified to, the blame to me lays with the Avanti procurement team!
There is a (non tilting) train of thought that Avanti backed themselves into a bit of a corner when they waxed lyrical at the select committee meetings about how they were about to recruit loads of new drivers & introduce new trains only to be asked, when? The whole introduction appears to have been a scramble with fragile training plans & lack of forethought regarding how the MU speed profile will work in practice. The fact that major questions only started to get asked at this stage suggests that there was a gap between collective decisions & responsibilities. Thats one opinion anyway.
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