# Video screen falls on dancers in Hong Kong



## gafftaper (Jul 28, 2022)

A large section of video screen fell during a concert in Hong Kong. There are multiple videos of the accident online. I link to the one below as it is the least disturbing. Other angles clearly show one dancer getting hit and it's really hard to watch. The wall came down directly on top of one dancer then fell over onto a couple of other dancers.

Rumors are that the one person is critical in the ICU and the dancers who were hit as it fell over only have minor injuries.

I'm guessing we will probably never know exactly what happened. Use quality components, do the math, check your work, use safety design factors, don't rig anything that you do not *KNOW* how to rig properly. Don't rig things in ways that are not manufacturer approved. Stay safe out there people.


----------



## Jay Ashworth (Jul 29, 2022)

NYT: https://www.nytimes.com/2022/07/29/world/asia/mirror-hong-kong.html


----------



## gafftaper (Aug 4, 2022)

The investigation appears to be focusing on the cables. Apparently some analysis of videos shows that this started when one of the cables broke. There are claims that rehearsals were delayed because of mechanical issues with the stage. 








Initial probe into accident at Hong Kong boy band Mirror concert to take 2 weeks; group calls for improving dancers' rights - Hong Kong Free Press HKFP

The initial probe into the accident that left two performers injured after a giant screen fell during a concert by popular Hong Kong boy band Mirror is expected to be completed within two weeks, a top official has said. The screen fell from height during Mirror’s live performance on Thursday and...



hongkongfp.com


----------



## egilson1 (Aug 5, 2022)

I'm also seeing some info that there is a "lost in translation" issue and it was a carabiner and not wire rope that failed.


----------



## gafftaper (Aug 5, 2022)

egilson1 said:


> I'm also seeing some info that there is a "lost in translation" issue and it was a carabiner and not wire rope that failed.


@egilson1 in typical US touring rigging practices, would the design factors call for the screen to be able to be supported by one cable if the other cable fails? 

From my semi-educated point of view, it seems like we are seeing a double failure here of 
a) Something breaks in the first cable system 
b) The second cable system should have been designed to be able to support the weight of the whole screen but it wasn't so it also broke

To me, the end result of this video _should_ have been a screen dangling awkwardly from cable number two. Is that a reality in typical touring things you see, or is that just my educational theater ivory tower ideal image of rigging that we don't actually see in the real world here?


----------



## Van (Aug 5, 2022)

I re-watched a couple times. It looks to me as if the screens were being lifted/ were rising at the time of the failure. It also appeared that the other two monitors were swaying slightly before the collapsed on let loose. the quality of this video makes it difficult to see if the lift line follows the screen down or if the cable separates at the top of the screen or if it snaps some where in the middle. 
I'm wondering if it was on a hoist and the hoist failed rather than just a cable or hardware failure.


----------



## Van (Aug 5, 2022)

Different angle with light and the aftermath. 
Hard to tell it could be that those are all signal and power cables that were wrapped onto the lift lines and the lift lines pulled through the center or, if, the hoist failed and cables still attached. 
I did notice in the other video that all the monitors were in motion and more than just this one were twisting slightly as the went up and down. That dynamic torsional stress on top of just the dead load might have been a factor.


----------



## soundman (Aug 6, 2022)

gafftaper said:


> @egilson1 in typical US touring rigging practices, would the design factors call for the screen to be able to be supported by one cable if the other cable fails?
> 
> From my semi-educated point of view, it seems like we are seeing a double failure here of
> a) Something breaks in the first cable system
> ...


The answer is - it depends. Thinking back to my last few tours where we had two point automated things either of the points would have held the load but the size of the object would have made it possible for it to have hit the ground. We had a flying camera on my last tour set up as a V rig between two winches. If the rope or attachment method would have failed from one line the other half of the system would have been able to support the load but the camera would likely crash into the ground because of the swing and amount of rope out. 

Another tour we had a large video truss that was on three points, if the center point would have failed the truss would have rolled but the outer two points could have held the load. Depending on where it was at the time of failure it could have hit the stage. If one of the outside points failed there would have been a 30' cantilever of 20"X30" truss supporting some video product. maybe it would have held? I don't think the engineering was run on such a failure. 

All the more reason from frequent inspections and choosing appropriately sized gear.


----------



## Ben Stiegler (Aug 8, 2022)

gafftaper said:


> A large section of video screen fell during a concert in Hong Kong. There are multiple videos of the accident online. I link to the one below as it is the least disturbing. Other angles clearly show one dancer getting hit and it's really hard to watch. The wall came down directly on top of one dancer then fell over onto a couple of other dancers.
> 
> Rumors are that the one person is critical in the ICU and the dancers who were hit as it fell over only have minor injuries.
> 
> I'm guessing we will probably never know exactly what happened. Use quality components, do the math, check your work, use safety design factors, don't rig anything that you do not *KNOW* how to rig properly. Don't rig things in ways that are not manufacturer approved. Stay safe out there people.



that is a weird news clip narrated by Robbie the RoboNarrator.


----------



## StradivariusBone (Aug 8, 2022)

Were the LED walls static or mobile? Somewhere I saw people were claiming they moved up or down or were tracked somehow, but I couldn't find anything specific to answer definitively.


----------



## gafftaper (Aug 8, 2022)

StradivariusBone said:


> Were the LED walls static or mobile? Somewhere I saw people were claiming they moved up or down or were tracked somehow, but I couldn't find anything specific to answer definitively.


If you watch the video from the really disturbing angle (not linked above but easy to find) you can see that the screen was in the process of slowly flying out when it fell.


----------



## Van (Aug 9, 2022)

StradivariusBone said:


> Were the LED walls static or mobile? Somewhere I saw people were claiming they moved up or down or were tracked somehow, but I couldn't find anything specific to answer definitively.


All 6 of them were moving up and down at the same time. I watched at least three other angles of the video and I have to say it looks like a couple of them were swaying/rocking around the z axis. I can't help but wonder if something got caught, a cable stacked wrong, something jumped a sheave. It just doesn't look right.


----------



## egilson1 (Oct 15, 2022)

Update







Wire 'fatigue,' installation and load caused screen to fall during Hong Kong boy band Mirror's show, task force finds - Hong Kong Free Press HKFP

The wire that snapped during a concert by Hong Kong boy band Mirror last month – sending a giant screen suspended by it plummeting onto the stage below – showed signs of “fatigue”, had been improperly installed, and its load was understated, a government investigation into the incident has...



hongkongfp.com


----------



## gafftaper (Oct 15, 2022)

egilson1 said:


> Update
> 
> 
> 
> ...


So sad that this was so easily preventable. Pounds are not the same as Kilograms and inspect your gear regularly.


----------



## What Rigger? (Oct 15, 2022)

That whole "claimed weight of the screen" vs "actual weight of the screen" thing took me back to the LA Auto Show in 2003. I had a curtain ring to hang for a reveal, and the motors were geared to the weight that the client told us. There were TONS of issues in getting this thing in the air, but at the 20 hours (in one day) mark we were finally ready to make it move. I flew it out, it got to its high limit and stopped perfectly. Then ten seconds later slipped in 3 feet all at once. 
Long story short, the client lied and right after that the LA Convention Center house riggers walked up with Sawzalls and said "Wanna solve ALL our problems?" and I went "Hell yeah, bruther!" and we did some emergency surgery. I got a lesson that has never, ever left me: KNOW how much something weighs before it flies, because clients lie when their mouths are moving.


----------



## Jay Ashworth (Oct 16, 2022)

Is it ridiculous to think about putting load cells in every hoist?


----------



## RonHebbard (Oct 16, 2022)

Jay Ashworth said:


> Is it ridiculous to think about putting load cells in every hoist?


*@Jay Ashworth* TUV and their buddies had loadcells on every hoist for every lift when I was in Offenbach in 1995. 
Toodleoo! 
Ron Hebbard


----------



## Jay Ashworth (Oct 16, 2022)

TUV the German government standardization organization?


----------



## Jay Ashworth (Oct 17, 2022)

BTW: Why was that screen only hung from two points?

If it had been on 4, it would probably not have fallen, and definitely not *on people*... right?

#IANAR


----------



## PerrierLoL (Oct 18, 2022)

Ben Stiegler said:


> that is a weird news clip narrated by Robbie the RoboNarrator.


there are so many free, less unsettling TTS voices out there smh


----------



## egilson1 (Oct 18, 2022)

Jay Ashworth said:


> BTW: Why was that screen only hung from two points?
> 
> If it had been on 4, it would probably not have fallen, and definitely not *on people*... right?
> 
> #IANAR


There can be a few reasons why the system designer decided on just two points. Without knowing more its hard to try and figure out what they were working with for variables. But a few examples might be:
1) Since they were using wire rope, we assume it was some form of winch system. could have been a drum winch with both lines running to a single groves winch. The more lines, the bigger the drum, the more space and fleet angle. The more "kinks" to work out...pun intended.
2) with only 2 lift lines, the load is "known" on each lift line, or what we call a "Determinate Structure". When you add more lift lines it becomes an "Indeterminate structure" meaning that the load shift between lift lines becomes much more difficult to predict and track. Obviously this is kinda a moot point, as they didn't have the real weight of the LED wall in the first place to determine the right sized hardware.
3) That evil thing called budget. syncing multiple single line winches is more expensive that a single multi line drum winch. But they are smaller and might fit in your truss better. I'm not sure what budget this show had, but I can imagine it wasn't low based on just the size of the rig.

I would also say this. had it been on 3, 4, more points, there is no guarantee that it would have stayed up, as we know they were way off on their loads and hence, their choice of materials and hardware. It's possible that they would have still overloaded the other lines in a chain reaction of failure and the same results would have happened.


----------



## Jay Ashworth (Oct 24, 2022)

Annnnnd.... that's why you're a certified rigger, and I'm not.

Fair enough.


----------

