Comments about technological history, system fractures, and human resilience from James R. Chiles, the author of Inviting Disaster: Lessons from the Edge of Technology (HarperBusiness 2001; paperback 2002) and The God Machine: From Boomerangs to Black Hawks, the Story of the Helicopter (Random House, 2007, paperback 2008)

Friday, December 17, 2010

Unstoppable and the Story of CSX 8888

The movie Unstoppable will add another heartwarming holiday movie tradition, the runaway train heading for a tank farm. The opening of the movie says it was inspired by true events. As in: loosely inspired by unmanned, runaway locomotive CSX 8888, dragging 47 cars through central Ohio on the afternoon of May 15, 2001. What railfans call the story of Crazy Eights was due to a combination of errors (most of them made in haste by the engineer) that exposed a loophole in the alerter, aka dead man switch.


This particular engine was an Electromotive SD-40-2. It followed all the basic principles of diesel-electric engines used on the high line:
  • They're powered by big diesel motors;
  • Those diesels turn generators;
  • The generators send power through heavy cables to traction motors in the sets of wheels below the main body of the locomotive;
  • When he wants to slow down, the engineer has a choice of three braking systems: he can (1) apply air-operated brakes on the locomotive itself (called the independent brake); (2) apply air brakes on all the trailing cars but only if the air lines are connected (called the automatic brake); or (3) reverse the operation of the traction motors so they act as generators, which makes each motor act like a brake (called the dynamic).
  • Since the reversed motors now act as generators, the energy has to go somewhere; while in theory it could be used to charge batteries hybrid-fashion, these would have to be very large so instead it's dumped to the air through giant resistance elements on the top of the locomotive. These are called braking grids. If you're standing on a bridge as a train passes under, you can see the big round openings that allow air through the grids. They look like window fans laid on their sides; the fans are to help pull the heat out.
  • Because steel wheels on steel rails have low friction, trains and individual railcars can start running away when unpowered, after mass and gravity have overcome brakes and other obstacles. Runaways under power are quite rare.
  • Guarding against this is the dead man switch or “alerter”, a fail-safe device to shut off engine power and apply brakes if the engineer fails to show any activity. On this model, that time span was 40 seconds … but only if it wasn't deactivated.
The movie had to jazz things up here, and simplify there. There wasn't a man lowered by helicopter; “Crazy Eights” didn't ram railcars or any other vehicles; the only injuries were minor, to the engineer; and it didn't almost fly off on a curve next to a tank farm. And the movie didn't explain the chain of events that set 8888 loose.

But there were many exciting aspects of the real incident that the movie drew upon: an attempt by police to use gunfire to hit the emergency shutoff (failed), an attempt to use a portable derailer (failed), and a chase from behind in which a locomotive latched on and used dynamic braking (which worked well enough, and better than shown in the movie). The train consist did include two cars with molten phenol.

While the chase was exciting, safety-lesson-wise the most interesting events all happened in Toledo's Stanley Yard, where the incident began.

Set aside the full track layout; concentrate only on three relevant tracks. Think of the capital letter “Y,” with a two-armed fork above and a stem below. The time is about 12:30 pm. As the story begins, the train is sitting in one fork of the Y, in the railyard. Because the train isn't complete as a “consist” yet, it needs to pull forward out of one arm of the fork into the stem, then come to a stop while the switch behind it is thrown; and then back up into the other arm of the fork to pick up some more cars. 

This is such a routine operation around railyards, where cars are always being shifted around, that the crews don't fasten the air hoses from the railcars to the locomotive, which would be necessary to operate the brakes on each car. (The movie shows this as an aberration, but it's a routine time-saver.) So the only way to brake this short-lived train will be to use the “independent” air brake on the locomotive. Once it's made up into a consist, the crew will make the train ready by hooking up the air hoses.


To move his train into the stem of the Y so it can be switched, the engineer throttles up. With just a few more cars necessary to clear the switch, a brakeman standing there calls the engineer on his radio and tells him to start slowing down, since the train has to stop and come back once the switch is thrown, to move into another track in the classification yard. No answer! In fact, the train gains speed to 11 mph.


The answer to this odd behavior can be found at the head of the train, a half mile away. The engineer had heard via radio that another switch in front of the engine, further along the stem of the Y, has been left in the improper position. He's moving too fast to stop short of it and he concludes that if the locomotive hits the switch as is, it's going to cause damage and delay. What to do? There's nobody up ahead he can radio to line the switch. 

The engineer decides in a flash that he will reset the controls to slow and then stop the train, but jump off before it stops, and dash ahead to reset the second switch himself. It's an odd decision for an experienced engineer, since engineers aren't permitted to jump off a moving train other than in cases of imminent collision.


His plan is to use all three braking methods to slow the train. He applies the independent brake on the locomotive. Normally the locomotive's brake shoes would be enough to stop the 3,000-ton train … but only if the engine was not producing force.


But he also tries to apply the train's automatic air-brake system and to engage the dynamic brake. These latter two actions are the immediate cause of the problem. I'll get to the reasons in a minute. Without time to check what he did, or tried to do, he jumps off the locomotive and sprints ahead, throwing the second switch with seconds to spare. He hears that the train is under power and sees that it is speeding up. So he tries to get back on board as the engine passes. But it's raining and he slips before getting aboard the engine. He is dragged a few dozen feet, then lets go. He puts out the alarm that a runaway train is heading south on the high line.


Controllers clear the path, police guard the crossings, and CSX tries to use a derailer on a siding to stop it. That fails. In the end, a chase locomotive catches up with it at Kenton, Ohio, and latches on. Using the dynamic brake, the crew slows it enough that an engineer can clamber aboard Engine 8888 and reset the controls.


The first error was that somebody left the second switch ahead of the train in the wrong position. That error forced the engineer into a hasty action that otherwise he wouldn't have taken.

The other errors were by the engineer. He inadvertently set the lever in “Run 8” position, which brought it to full power, instead of setting up the dynamic braking. It wasn't a good idea even to try to use the dynamic, since it's something to use on the high line at speed, rather than while crawling around a trainyard. Proper procedure would have been to bring down the throttle and apply the independent brake, accepting any damage to the switch as the lesser of two evils. It wasn't the engineer's problem to solve.

So why didn't the alerter, the deadman switch, automatically shut down the locomotive after just 40 seconds of inactivity by the engineer, before it even left Stanley Yard? Because the engineer had tried to apply the automatic air brakes along the length of the train. They weren't connected so they didn't work; worse, just the attempt to apply them raised the brake pipe pressure and disabled the alerter. The reason for this loophole is that engineers sometimes have to set the brakes and get off a locomotive after it stops, and they want to leave it running rather than have it shut off automatically.

With power in Run 8, the only force holding back the locomotive was the locomotive's independent brakes. Those brakes were of little effect against a full power setting, and even less effective after they burned off entirely.

3 comments:

  1. Thank you . However the movie Runaway! (1973 has almost the identical plot. Ice forms in an air valve on a excursion train on a steep grade. After several attempts to stop it, heavier locomotive couples on to the rear to apply breaking.
    This movie was made decades before 8888. Is it based on an actual incident ?

    ReplyDelete
  2. There was also an Indian film called the burning train(1980), which was too an excellent movie �� with an interesting story line.....

    ReplyDelete
  3. There was also an Indian film called the burning train(1980), which was too an excellent movie �� with an interesting story line.....

    ReplyDelete