From: ahk@chinet.com   
      
   John Albert  wrote:   
      
   >I downloaded the pdf format of the Lac Megantic report.   
      
   >It goes on for around 191 pages (in pdf format), but most of   
   >it is irrelevant as to answering the question, "why did the   
   >train move?"   
      
   >That answer can be found on page 23, in Table 1, "Locomotive   
   >event recorder information".   
      
   >Evidently, the engineman made a grave mistake in leaving his train the   
   >way he did. This mistake may not have been an intentional, but if he had   
   >done ONE MORE THING [re-apply the automatic brakes] -- even though the   
   >number of hand brakes was insufficient to hold the train -- the train   
   >would not have moved within the time frame it did, even though there was   
   >no longer  enough (or any) locomotive air pressure to keep the locomotive   
   >independent brakes applied. . . .   
      
   Thanks for the explanation. Given the completely worn brake shoes on   
   several of the locomotives (hand brake application applies just 2 of 12   
   brake shoes), I take it leaving automatic brakes applied would have left   
   all 12 shoes applied on each locomotive, partly making up for some of   
   the bad brake shoes that would worn beyond usefulness.   
      
   I read the whole report yesterday, except for the pages on the fire itself.   
      
   Several questions on what you wrote:   
      
   I take it that the automatic brake application and the independent brake   
   application are controlled separately. Are there two separate brake   
   handles?   
      
   The report went through the actions of the Quick Release Brake (QRB) valve   
   on the GE locotives, 3 of the 5 locomotives in the engine consist. To   
   engage the hand brake, the air must be dumped, which is what the QRB valve   
   does. A brake chain connects the hand brake wheel to the QRB valve; one   
   of the QRB valve because of temporary maintenance performed had to be   
   released manually, but the engineer didn't know to do this. I take it this   
   dumps the air in the automatic brake cylinder without dumping the air   
   in the independent brake cylinder, right? Does this mean that the independent   
   brake was still applied in the GE locomotive with the faulty QRB valve,   
   at least until the air pressure dropped in the independent brake cylider?   
      
   I take it the other two locomotives don't have QRB valves. Cars themselves   
   wouldn't have QRB valves, right? In these situations, is the air still   
   dumped in the cylinder that maintains automatic brakes in order to apply   
   the hand brake?   
      
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