Faulty brakes cited in California Screamin' accident

I've read the report now, too. Based on it, it's not clear to me that maintenance would detect the valve failure----it can only be seen with fully-loaded trains during a block zone test, and even then I don't think the failure is deterministic---it may only happen once in a blue moon.

If fault can be apportioned, it seems to me that it would be either the manufacturer of the valve (mis-reporting its performance characteristics) or the engineer who chose that particular valve for this particular application. As the manufacturer bulletin came from WDW to DLR, I'm guessing that this brake zone is oen added by Disney post-handover from Intamin.

So, not really a maintenance issue, but a subtle design flaw that may or may not have reasonably been forseen.

Since the LA Times has mentioned that Disney has notified the industry about the leaky valves I suppose there is no harm in posting the direct link to the brake valve bulletin here. It's posted on the NAARSO web site.

--Dave Althoff, Jr.

Thanks for the links Dave. The bulletin is very well written where a layman can understand it.

Sucks to be Disney right now.....

I wondered when the bulletin first appeared; I was a bit surprised that a Disney bulletin would make it outside their organization, then I saw the LA Times story. Obviously the bulletin is written for Disneyland, but written to draw attention to the possible problem to anybody in the industry who has that kind of a brake mechanism. This is the way ride safety SHOULD be handled.

--Dave Althoff, Jr.

...should add as well that Kathy Fackler scored some points for *praising* Disney's response in getting the word OUT in the industry. Perhaps Intamin themseleves coulda taken the lead, but that would be akin to admitting there was a problem in design....

Points also to NAARSO..."safety through communication"... :)

Ah, Gator, but if you read through the LA Times story, you will see that Disney changed out the Intamin valves as part of routine maintenance and used Legris valves which were recommended by a parts supplier as offering equivalent performance, probably at a reduced cost. Disney can do that because from a legal standpoint, Disney is the manufacturer (and you will note that it was Disney that issued the maintenance bulletin).

Intamin's logical response would be, "See, this wouldn't happen if you would use only genuine Intamin-supplied replacement parts."

This time, Intamin is off the hook for a change.

--Dave Althoff, Jr.

But Dave, didn't Intamin *design* the coaster so that a faulty valve would result in OPEN brakes?

Proper design, at least in my mind, wouild mean that a *fault* in the circuit anywhere along the system (either electronically OR mechanically) would result in every train "locking up" in the next block?

If that were the result, then a "ghost train" as on BTMRR or a faulty valve as on CS would STOP the train at the next braking section, and no *collisions* would happen....or so it would seem.

Again, Dave is WAYYYYYY more knowledgeable about the actual working of said mechanicals, I'm just a really PIA troubleshooter...or so my programmers tell me... :)

Remember, though, that this is a mechanical failure that was induced by a triggered block stop. The brake was closed because the control system had already ordered the brakes closed (for whatever reason). The train enters the brake, and on entering the closed brake, triggers the mechanical fault. This means reduced braking performance in the block where the train was expected to stop, allowing the train to proceed and to collide with the train already stopped in the next block. A detected ghost train or faulty valve would stop the train at the next braking section, and in fact that is what happened. The controls ordered the brake to close, the calipers closed, and most likely, a prox switch on the caliper reported back to the computer that the brake was closed (which, according to the scenario in the bulletin, it was!). Along comes the train, shoves the caliper open, blowing the dump valve open, allowing the brake to open and the train to proceed right through the block where it was expected to stop.

There is no way to detect this kind of a failure until it happens, and when it happens, it's too late to do anything about it. About the only way to avoid a collision would be to somehow detect that the brake had failed, and then respond by moving everything forward one block. But that would not be a safe response as it would require the safety system to initiate unexpected movement of the vehicles, which is in violation of accepted practice. I'm afraid you have to, as Jeff put it, file this one under, "$#!+ happens." Best laid plans of mice and all that, you know.

--Dave Althoff, Jr.

.....and finally, the light bulb goes on...

Thanks for your patience Dave...LOL!