The situation is better explained by the NTSB, rather than ‘Freightwaves’ summary.
https://www.ntsb.gov/investigations/AccidentReports/Reports/RSR1902.pdf
I have alway felt the air hose configurations on long cars (Auto Racks etc.) were Rube Goldberg at best and dangerous when things varied out of their original specifications. Too many feet of hose to account for cushion-frame drawbar configurations.
Thank You for this information.
Many things can happen.
I once had a auxiliary air hose (for operating the bottom doors on a hopper car) reach over and close the angle cock on the next car.
Fortunately this was on a light train, and we were not descending any steep grades.
This accident is really a two fold problem. The kinked trainline prevented the Emergency Application from being propgated from the locomotives and for whatever the reasons the locomotives did not have contact with the EOT so that the Emergency Application could be initiated from the EOT.
I don’t know at what speed the initial attempt was made to put the train in Emergency - I heard 30 MPH mentioned. In prior NTSB investigation of runaways on mountain grades they have documented that at speeds above 12 MPH, coal trains with 286K loads will have their air brakes fade away as the tonnage and speed overpower the brakes by generating more heat than holding power.
Reading the NTSB document, the fact that the airflow to the train line when stretched was about 27 CFM and went to zero when the train bunched raises the following question: did that 27 CFM flow continue, albeit to the rear of the probable kink, and what effect would that have on the eventual brake applications, even if the ETD did manage to dump the air? (Or, was that 27 CFM going out the ETD turbine?)
Too slow a reduction will not apply the brakes, but could leave the brake pipe pressure at zero, meaning that dumping the air from the rear of the train would have no effect, even though the emergency reservoirs on the cars would still be fully charged. This is from practical experience.
This does beg the question of what the EOTD was sending to the head end for a pressure at the rear of the train. The report states that the crew did not see the application at the rear of the train when it was made, but does not mention what pressure was displayed. One might think that if a pressure substantially lower than the expected was seen on the Head End Display, that would have been factored into the investigation.
That it took three tries to dump the EOTD speaks to communications difficulties between the head end and the rear of the train, which may be a factor in what was displayed on the head end as well. Of course, that they were able to dump the train with the EOTD indicates that there was still pressure on the brake pipe.
Air turbine EOTs usually don’t use enough air to show flow on the engine. Changes in air flow aren’t unusual, although usually the flow rises when the slack is bunched. We call it a ‘slip joint’. In this case the leakage was behind where the hose was kinked or pinched.
I had this happen to me coming over the summit at Omaha a few years ago. I had a manifest with about a 115 or so cars. We crested the summit at 15 mph, my usual practice with most trains. I was in dynamics when I made a minimum application on the automatic brake, about a 7 or 8 psi reduction. The EOT didn’t change, which isn’t unusual there due to comm loss. We picked up about 1 mph when I increased the air brake application to a total reduction of 10 psi. Still no change on the EOT, so I hit the comm test button. It showed that we had comm with the EOT, and about that time the EOT dropped by 1 psi. It had been about 88 psi to begin with. I knew then we had a problem, that we had a blockage of some kind, which I told the conductor.
I increased dynamics to full and increased the air brake application to full service. We were running on clear signals, the grade is about 3 miles long. My accelerometer showed we were beginning to slow, never getting over 17 mph, so I told the conductor I intended to ride it out. I said if conditions changed we had the option of dumping the EOT and using emergency braking.</
Thanks for the insight, Jeff. I knew some rail would fill in some of my knowledge gaps (I was guessing or hoping you would chime in). Your narrative of the kinky problem and how you handled it was a nice peek into your “office” as well.
Now I can chew on why flow might go up when slack bunches, but maybe after I get up in the morning.
Interesting thought based on your narrative is how unlikely a software solution would be able to handle the particular situation. We called them “corner case” situations and it was amazing how many revealed their ugly heads when we put the software on the plane and let the monkeys, I mean pilots, use it. Fortunately, we never dumped a plane because of it, but there were moments…
Jeff, your insight is invaluable. Thanks.
You ought to write a book!
[quote user=“jeffhergert”]
Air turbine EOTs usually don’t use enough air to show flow on the engine. Changes in air flow aren’t unusual, although usually the flow rises when the slack is bunched. We call it a ‘slip joint’. In this case the leakage was behind where the hose was kinked or pinched.
I had this happen to me coming over the summit at Omaha a few years ago. I had a manifest with about a 115 or so cars. We crested the summit at 15 mph, my usual practice with most trains. I was in dynamics when I made a minimum application on the automatic brake, about a 7 or 8 psi reduction. The EOT didn’t change, which isn’t unusual there due to comm loss. We picked up about 1 mph when I increased the air brake application to a total reduction of 10 psi. Still no change on the EOT, so I hit the comm test button. It showed that we had comm with the EOT, and about that time the EOT dropped by 1 psi. It had been about 88 psi to begin with. I knew then we had a problem, that we had a blockage of some kind, which I told the conductor.
I increased dynamics to full and increased the air brake application to full service. We were running on clear signals, the grade is about 3 miles long. My accelerometer showed we were beginning to slow, never getting over 17 mph, so I told the conductor I intended to ride it out. I said if conditions changed we had the option of dumping the EOT and using emergency braking.
We stopped by the Amtrak depot in Omaha. I notified the dispatcher we had stopped and why, and that the conductor was starting to walk the train. The dispatcher said he would have a car man come out and assist.
After a few minutes the conductor called on the radio to ask if the brake pistons should be in or out. I said they should be out. He had found some that were in, and back tracked to where the problem was.&nbs
If I had had a DP consist, either in the middle behind the blockage or at the end of the train, the brakes would’ve applied normally if I had comm with it. The blockage wouldn’t be noticable unless in that situation unless we would stop with the slack bunched.
When a DP train stops, it’s required to do a ‘train check’ before departing. A train check cuts out the brake valve on the DP units. When the air brake is released, the DP units need to register a brake pipe pressure rise at a certain rate. If they do, they cut themselves back in and start pumping air, and give a ‘train check-OK’ message. If they don’t see the rise after a set period of time, the DPs remain cut out and a ‘train check-fail’ message is given. That could be an indication that an angle cock is closed or the brake pipe is otherwise blocked. There can be other reasons why it might fail, so usually we’ll retry the test. If it fails multiple times it’s probably time to start walking.
A DP on the train in Wyoming may not have helped. If the EOT was not in communication with the head end, the DP probably also would’ve been in comm-loss. (On another site, guys from that area said comm-loss in that area is normal. There are places where for whatever reason, comm-loss is an almost everyday occurance.)
In comm-loss on a DP, it’s registered immediately, The head end device on an EOT counts down 16 1/2 minutes before registering the loss. After 16 1/2 minutes, trains have to reduce speed to 30 mph until comm is restored. (The issue is actually not the comm-loss. but the ability to initiate an emergency application on the rear end of the train. Comm could come back, but if the EOT disarmed itself you would still be restricted to 30 until it could be rearmed. Heavy grade operations have stricter restrictions than those.)
In the Wyoming situation, a DP behind the blocka
Jeff; thank you for that comprehensive explanation! Very much appreciated!
I know virtually every territory has ‘black holes’ in communications somewhere along their routes - even in ‘flat land’ areas.
I have never fully understood the permissible delay logic in the communications between the Head End and the EOT. On CSX the permissible amount of no-com time was 15 minutes then s
The Government has been emphasizing rural broadband access recently, culminating in a $4.9 billion initiative through the FCC that started only recently. If there is any kind of proven interference – and judging by my experiences with HDSL and similar technologies, there can be several types – with the RF integrity either for DPU or EOT, it needs to be related to the relevant folks at the FCC as quickly as possible, ideally with as complete a description of the circumstances and history as can be provided.
Unlike the situation with imposing high-data-rate modulation on powerlines, I think the RF interference effects of broadband on railroad frequencies should be ‘fixable’ once recognized – and it’s commercially important, verging on critical, that those bugs get ironed out before substantial investment in rural broadband equipment and services is advanced ‘following the new money’.
Propogation can vary, too. As a ham radio operator, I know that sometimes a repeater that I use for a local net will come booming in, and others it barely registers. It can even vary during a net.
The DPU radio frequency could also be subject to interference from public safety, and other, agencies. It’s only a couple mHz off our county trunked radio system here.
There could also be issues with harmonics from broadcast frequencies - I encountered that while I was running a government trunked radio system. In fact, that could help explain certain “black holes.”
And, we have an area in our county where the local geology has an effect on radio signals.
Such areas could be easily investigated, if the RR chose to do so.
Gee, that’s bad. Even a freight running at 40 mph will cover ten miles. Plenty of time and distance for a disaster.
In the broadcast world, I think the FCC has attenuated their monitoring and inspection efforts.
Back “in the day” you would see the regional enforcement unit show up once a year, usually. When they appeared at the station, they had already been monitoring your signal for a few days and if there were problems, you found out about it in the notice of violation. The inspection was mainly to see if your logs were all ship shape, your tower paint was not deteriorated, and if you had the required spares on hand. It’s been many years since I was last involved with a station, a lot of things technicaly have been deregulated and from what I gather the boys from the commission don’t show up nearly so often, though once in a while they smack a low-power broadcaster around a little bit.
With the system displaying the information that the train line flow was fluctuationg with slack action, why would an engineer not stop immdedately upon discovering this displayed information? As I understand it, this flucation was discovered long before the encounter with the grade where the train ran away. Wouldn’t this fluctuation be a major “red flag” that train braking may be unreliable if called on for maximum performance on a long, descending grade?
Not really.