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Re: What is Known So Far
Author: Burr Wilson
Date: 09-18-2013 - 09:43
I've been following this thread with interest toward understanding what could have caused the runaway to occur. There's been speculation about how the train's brakes released an hour after the train was tied down on the main. I've questioned how this train could have remained stationary while the engineer was out of the cab tying the train down.
Will, you're first to publicly posit that locomotive independent brakes were used to hold the train while it was being tied down and then left unattended. Bingo, I think there's the key piece of information that leads to understanding how this runaway occurred ... independent brakes were holding the train, in addition to the reported 11 handbrakes in the consist!While the independent brake system applies straight air against each of six axles, the handbrake operator acts on one cylinder lever.
So, here's a possible explanation as to the sequence of events; The train was stopped on the main track at Nantes using the independent brake, not the train-line air brake system. The independent braking system was applied on five MU'd locomotives of various make and model. All locomotives featured six axles with 6 brake cylinders and pistons (that's one brake cylinder per axle), for a total of 30 operative brakes in locomotive MU set. The engineer left the lead unit cab and walked through the locomotive consist, applying the handbrake on each trailing locomotive unit and shutting down each engine to reduce fuel consumption. This left the lead locomotive unit and its air compressor solely in charge of keeping up the main air reservoirs throughout the MU consist and maintaining the independent brakes of MU'd locomotives. After the engineer left this train, fire department emergency personnel responded to a citizen's report of an engine fire (reported to be caused by a broken piston in the lead unit's engine) and likely performed a standard shutdown protocol, by pressing one of its emergency fuel cutoff switches and perhaps opening the main battery knife switch.
After the departure of emergency responders, the locomotive and train are unattended. There is no competent personnel present to observe that main reservoir air is bleeding off, allowing the eventual release of independent brakes of MU'd locomotives. Consequently, braking force is slowly reducing below the critical threshold for holding the train against a 1.2 % grade, and eventual bleed off of independent brakes on the locomotive MU set overcomes the stationary braking force of locomotives' single axle handbrakes, resulting in this tragic situation now being ascribed to "insufficient handbrakes applied". (It's reported that engineer also applied hand brakes to 5 of the cars in the trailing consist - that's still insufficient handbrakes applied.)
It will be interesting to read the safety officials' final report on this incident, and pick out each of the singular events that accumulated into the full-blown disaster.
Will, you're first to publicly posit that locomotive independent brakes were used to hold the train while it was being tied down and then left unattended. Bingo, I think there's the key piece of information that leads to understanding how this runaway occurred ... independent brakes were holding the train, in addition to the reported 11 handbrakes in the consist!While the independent brake system applies straight air against each of six axles, the handbrake operator acts on one cylinder lever.
So, here's a possible explanation as to the sequence of events; The train was stopped on the main track at Nantes using the independent brake, not the train-line air brake system. The independent braking system was applied on five MU'd locomotives of various make and model. All locomotives featured six axles with 6 brake cylinders and pistons (that's one brake cylinder per axle), for a total of 30 operative brakes in locomotive MU set. The engineer left the lead unit cab and walked through the locomotive consist, applying the handbrake on each trailing locomotive unit and shutting down each engine to reduce fuel consumption. This left the lead locomotive unit and its air compressor solely in charge of keeping up the main air reservoirs throughout the MU consist and maintaining the independent brakes of MU'd locomotives. After the engineer left this train, fire department emergency personnel responded to a citizen's report of an engine fire (reported to be caused by a broken piston in the lead unit's engine) and likely performed a standard shutdown protocol, by pressing one of its emergency fuel cutoff switches and perhaps opening the main battery knife switch.
After the departure of emergency responders, the locomotive and train are unattended. There is no competent personnel present to observe that main reservoir air is bleeding off, allowing the eventual release of independent brakes of MU'd locomotives. Consequently, braking force is slowly reducing below the critical threshold for holding the train against a 1.2 % grade, and eventual bleed off of independent brakes on the locomotive MU set overcomes the stationary braking force of locomotives' single axle handbrakes, resulting in this tragic situation now being ascribed to "insufficient handbrakes applied". (It's reported that engineer also applied hand brakes to 5 of the cars in the trailing consist - that's still insufficient handbrakes applied.)
It will be interesting to read the safety officials' final report on this incident, and pick out each of the singular events that accumulated into the full-blown disaster.
