Amusement Park ride tragedy 9

[Brian Malone]

https://youtu.be/ozhnXp9OWEk

A 14 year old was killed when he slipped out of the restraint harness on this free drop ride. He was a very large teen - more than 6 ft tall and about 340 lbs. From what I have seen in other stories, he exceeded the ride manufacturer's stated weight limit.

This looks like it may be a case of additive errors leading to a bad outcome:
1. It appears the over- shoulder restraint bar/harness did not have an interlock for ensuring proper latching before allowing the ride to function. Or if an interlock system exists, the interock did not work.
2. Ride operators did not check all rider's harnesses status prior to starting the ride.
3. The ride operator appears to have discounted the kid questioning why there was not any 'click'
4. The ride operator(s) either ignored the allowable weight limit for riders or were not trained to enforce the limit. Chances are there may not be a scale in the entry queue and the operators have to use a visual estimation of rider's weight.
5. Apparently the ride does not have seatbelts as a redundant safety measure. There appeared to be some questioning about a seatbelt.
6. The young man may have become anxious as the ride rose and he moved toward the front edge of the seat or pushed up on the restraint/harness in an attempt to ease his anxiety and thus changed his body angle and CG relationship, thus moving out of the cup of the seat. Anxious or not, by the very motion of the ride his body would react against the over- shoulder restraint bar/harness during the drop and if it has a rotation axis to ease entry and it was not locked it would be free to rotate and reorient the young man's body angle in relationship to the seat. Upon deceleration, the kid just slid out under the restraint.

The details are still unckear but this ride is a new construction so it will be interesting to see the failure report.

 

[LionelHutz]

I find it hard to believe they would design the locking systems so it would lock with the shoulder harness so far out there is a big enough gap between it and the seat that someone can submarine out of the seat. I would think the seat and notch in the restraint would have to be together before it would latch. It'd be a very stupid design flaw to latch it with a big opening.

I tend to think it was a false latched indication. I wonder if he had shoved the restraint open on the way up if the ride would have aborted?

 

[Debirlfan]

Park is claiming the restraint was locked. Unless the restraint has more than one position in which it can lock, then I don't buy it. Photos of the boy on the ride clearly show that his shoulder restraint is up higher than anyone else's. I suspect it wasn't latched, but after he fell, the braking and 'impact' of the stop at the end of the ride was enough to settle the restraint into its latch.

 

[LittleInch]

Most have some sort of ratchet and a number of locked positions to account for the different sizes of people.

If you look at the photo of the seats with no one in I posted, you can see in an empty situation the shoulder restraint is locked way behind the upstand such tat anyone in it would need to be about 6" thick.

The question is then did the largest setting on the restraint allow someone to submarine out of it and did it in fact lock them in tight enough to start with.

I'll be looking harder at these seats the next time I go on one.


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[SwinnyGG]

The question is then did the largest setting on the restraint allow someone to submarine out of it and did it in fact lock them in tight enough to start with.

There's an important sub-question that I haven't seen asked yet..

The victim here was well over the published passenger weight limit for the ride. If the restraint is locked on the largest setting but the passenger being restrained is at or under the weight limit, is submarining still possible?

 

[Roga50]

I tend to think it was a false latched indication. I wonder if he had shoved the restraint open on the way up if the ride would have aborted?

Page 115 of the operating manual seems to indicate that a seat that becomes unlocked will trigger a Warning--not an abort. I believe "Z-Stop" would effectively be an "abort" but returning the ride to the unloading position would be performed manually by the operators (in the manual, they detail this as "evacuation mode" in another section).

 

[dik]

...and the 16 year old kid in charge obviously read the manual.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[Cool_Controls]

Is it possible the rider was holding the restrant bar down but it wasn't able to latch but was able to close the limit switch? (Badly positioned proximity switch or proximity switch with a washer taped to it) In my experience PLCs aren't much for logging unless there is a software package or an HMI connected to it, considering the level of complexity (seperate safty PLC) an HMI seem very likely. Hard to imagine you could start a ride cycle with a unlatch signal active.

 

[IRstuff]

There are LOTS of rides with age, height, or other restrictions; I recall an acquaintance that hosted a birthday party for their kid at Disney, but he was too short for a number of rides. There was presumably a weight/size limit on the ride in question. How the victim got through that wicket is a problem, followed by the sequence of events relative to locking the restraints. Nevertheless, had there been a serious safety culture at the park, the victim should have been barred from the ride if there was even a hint of issues with the restraints.

TTFN (ta ta for now)
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[dik]

Nail on the head, IRS...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[LionelHutz]

You would sure hope that the locking indicators checked that the locks were engaged and not that the bar was only down a certain amount. I find it very hard to believe the designers would be that stupid.

 

[Brian Malone]

It's absolutely astonishing that no testing exposed this design flaw. I question whether these over the shoulder systems were even intended for use in this orientation.

It will be surprising to find the Funtime Group engineers did not do sufficient boundary testing to uncover the safety flaw of the potential for an over-sided rider to submarine out of the restraint. The engineering on these type of rides is very complex and the teams that design them are highly skilled. It does appear as others have pointed out maybe the hazard induced by adding the 'tilt outward' feature was not caught or overlooked? With the ride chair sitting at the starting angle an over-sized rider's CG is probably inboard of the point of restraint created by the over-shoulder restraint and the chair cup and upriser. When the 'tilt outward' position is created by an active drive operation at the top of the lift just before the drop the over-sized rider's CG could be inline with or outside the point of restraint created by the shoulder restaint/seat system. Thus allowing a slide condition to be possible with greatly reduced normal force creating less friction to keep the rider in place. A 'normal' size rider's CG or 'under-sized' rider's CG would never move to be coincident or outside the point of retention. I am not familiar with the safety requirements in the amusement ride industry but in the medical world consideration for mitigating normally expected misuse/improper use of a system is common and often debated on how far must mitigation be conducted to protect those who may knowingly or sometimes unknowingly put themselves or others at risk.

 

[Cool_Controls]

The CG of an object does not change with orientation,

 

[Alistair_Heaton]

I believe it can move in the human body.

Mostly due to fluid movement.

 

[Brian Malone]

I should have been more clear - the line of action of the CG in relation to the acceleration. point of retention.

 

[LittleInch]

I think you might be surprised at how few engineers there are in those companies.

Any that can sign off not having a seatbelt attachment which would prevent accidental submarining for what would be incredibly minor additional action should be worried.

It would also act as a go/no go if the belt didn't attach because the shoulder restraint wasn't down far enough. I've seen that in action on rides I've been on and it works.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Brian Malone]

I think you might be surprised at how few engineers there are in those companies.

That is surprising - my impression is formed mainly by stories describing the high level of stress analysis and simulation that goes into theme park ride design. Often the credentials of the teams described are quite impressive.

It would also act as a go/no go if the belt didn't attach because the shoulder restraint wasn't down far enough. I've seen that in action on rides I've been on and it works.

Yes, a simple additional belt mitigates submarining and reduces the risk dramatically.

 

[dik]

From the partial printout of the error codes, it may be a user/operator error. We have to wait and find out...


ditto...


It might be like having a seat belt included with a 'baby carseat', in addition to the restraint. It may be unnecessary... we have to find out. It may be with the accellerations involved, the seat belt may be dangerous. The restraint may be 'foolproof', realising fools can be ingenious.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[IRstuff]

That is surprising - my impression is formed mainly by stories describing the high level of stress analysis and simulation that goes into theme park ride design.

Safety analysis and design often takes the short shrift when it comes to design; it's often applied only after the main structural and functional design takes place.

TTFN (ta ta for now)
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[Cool_Controls]

 

[IRstuff]

I don't see that as a smoking gun; the issue is whether the victim was covered by the requirements. If no, then the design wasn't specifically an issue; it would be no different than if someone followed seismic design requirements, and the "Big One" turned out to be 10x bigger than the requirements. The usage and operator control would still have been an issue, regardless.

TTFN (ta ta for now)
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