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| Re: Possible cause of Amtrak Derailment (could two earlier incidents have played a role) (1352071) | |||
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Re: Possible cause of Amtrak Derailment (could two earlier incidents have played a role) |
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Posted by Bill West on Fri May 15 02:52:54 2015, in response to Re: Possible cause of Amtrak Derailment (could two earlier incidents have played a role), posted by SelkirkTMO on Fri May 15 01:04:04 2015. Hi Unca Selkirk, I was just going to write that I pulled up Google Earth, turned on the railroad layer and backed the view out so I could see from 30th to Tacony. Two things were interesting:-after you hang a right at Zoo and turn northeast the ROW is at about 100ft elevation (+/-10ft) through North Philadelphia all the way to N 2nd St and the curvature is mild, even the one at N 2nd wouldn't be a problem at 70mph. -from N 2nd to the Frankford curve the elevation drops to about 40ft, the 1943 ICC report says that's a 0.6% downgrade. And of course we know that the curve at the end is a problem. So in line with your NTSB info I have to wonder what speeds would occur if one stepped on the gas leaving Zoo, wound up for 4 miles through N Phila to N 2nd St and then for some reason didn't cut back the throttle entering the downgrade to Frankford? Maybe with the power on, an acceptable 70mph at N 2nd would just naturally reach 100+ entering the curve at Frankford. The NTSB's 70 to 106mph over 65 seconds covers 8400ft, that reaches back to B St, 2000ft east of the N 2nd St curve. The 3 second emergency braking when added to a 1 second reaction time at 106mph is 600+ ft and reaches from the point of derailment back to the start of the curve (or if the event recorder didn't quit until the locomotive stopped sliding then it only fits from there back to the point of derailment). So maybe our acceleration represents inaction rather than conscious action. And the braking started with seeing or feeling the curve. With regard to the windshield I notice that the engineer's right pillar has been smoothly but very thoroughly wacked. To me that excuses the straight cracks and your flying ballast easily covers the star cracks. The other interesting thing in the front pictures is that the dash padding seems to have been tossed about. Did our engineer get strongly thrown into it? Lastly I reread Jersey Mike's Wikipedia article on Pulse Code Cab signals. The PRR version applicable here compares codes to locomotive speed and whistles conflicts but only for the restrictive signals, where there are defined speeds. For a clear track it tells the engineer that he can use MAS but as that doesn't have a single definition and varies with location the system can't check on him and so doesn't whistle. As 188 had a clear track the system only knew that speeds above 45 were okay but didn't know whether 70, 125 or 50 were the applicable MAS. After all the original purpose was to counter accidents occurring because of failure to observe signals regarding junction routes or conflicting traffic, not the then lesser problem of obedience to basic ETT speeds. Road Foremen and Dispatcher's train sheets seemed to have covered that and very few trains regularly reached 90mph let alone 106. So all 188's engineer got was a MAS indication, no system imposed limitations on what that was. Bill |
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