UPS 744 Tail tips in Seoul while parked

[psolk 3,040]

My first thought was cargo loading incident but looks to be a gear issue.  Center landing gear seems to be retracted while the wings are still clearly down. Looks like the issue actually began in the air and they returned to Seoul.  Apparently it leaked hydraulic fluid onto the tarmac and stripped some tail paint as well.  Thankfully no one injured. Also good photo on a-liners.net I can't link due to copyright.  

https://aviationsourcenews.com/general-news/ups-airlines-boeing-747-400f-tips-its-tail-at-seoul-incheon-airport/?utm_source=rss&utm_medium=rss&utm_campaign=ups-airlines-boeing-747-400f-tips-its-tail-at-seoul-incheon-airport

https://www.aviation24.be/airlines/ups-airlines/boeing-747-400f-tail-tips-at-seoul-incheon-airport/

 

[darrenvox 135]

ooops

[fluffyflops 1,858]

there was another airline with jumbos that did that a couple of years ago with bad loading, down in the middle east.

I forget who it was.

[jon b 2,050]

A number 1 system hydraulic problem then, if it was the hydraulics.

A nose up situation like that on the passenger variant also renders the L&R one door slides unusable 

Just mumbling to myself trying to remember things , amazing how quickly you forget.

[psolk 3,040]

12 hours ago, fluffyflops said:

there was another airline with jumbos that did that a couple of years ago with bad loading, down in the middle east.

I forget who it was.

Yep, I also assumed it was a Cargo load issue.  We just saw the United 737 tail tip due to CG while unloading the plane without it's tail stand.  Any time I've seen a plane sitting like that on the ground it's been cargo load.  This is the first time I've seen one where the hydraulics failed causing the tail tip... 

10 minutes ago, jon b said:

A number 1 system hydraulic problem then, if it was the hydraulics.

A nose up situation like that on the passenger variant also renders the L&R one door slides unusable 

Just mumbling to myself trying to remember things , amazing how quickly you forget.

Thanks @jon b was hoping you'd chime in.  Tough to figure (for me with no knowledge) out how the mains went down just sitting there but the wings remained extended.  Apparently the crew noticed the issue in the air prompting the return to Seoul and they were able to land fine thank goodness!!!  I'd imagine anyone sitting in the cockpit would get quite the shock when the nose went airborne! The picture on the other site shows some paint damage under the rudder from the hydraulic leak as well... 

Edited October 29, 2021 by psolk

[jon b 2,050]

There's obviously a bit more to this story as it says the incident happened during parking. I don’t know how accurate “ during “ parking is though. 
loosing the number 1 hydraulic system will also kill the nose and body gear steering so it would have required a tow in from the runway. Maybe they did tow her in and when the tug disconnected from the nose wheel that’s when it tipped back, but that should have been anticipated so I doubt that was the case.

It is reported as being empty of cargo but having fuel to fly to Germany, so due to the nature of the swept wing the C of G would be quite aft causing the tail to tip.

Again if the number 1 hydraulic was lost in flight they would have done an alternate nose/body gear extension( and deploy the flaps in the slower secondary electric mode)  , this is basically an electric motor powered by the number 4  electric bus which pulls out the up locks allowing the gear to free fall and lock into down. If the body gear didn’t lock down the crew would be aware of this and precautions to prevent a tail tip put in place.

The down locks are held in place by springs I believe so once they’re down even loosing hydraulics shouldn’t allow the gear to retract.

Its interesting to see the GPU cables are long enough to allow for this sort of thing without the GPU being pulled into the air.

On the flight deck when this sort of incident is imminent an early indication is the APU generators drop off line. What happens is as the nose wheel oleo starts to extend as the tail starts going down it triggers the air/ground logic sensor in the nose oleo and the aircraft thinks it’s airborne and trips the APU generators.

It will be interesting to learn what actually happened as more details emerge.

@psolk Paul on a separate subject I may need to PM you at a later date for some advice if you don’t mind. I’m about to buy a new sim rig and my 13 year old is salivating at the thought of getting my old PC for his motorsport simulation hobby, which is currently on the x-box. He’s talking about getting new wheel bases and other things I don’t understand .

[psolk 3,040]

6 minutes ago, jon b said:

There's obviously a bit more to this story as it says the incident happened during parking. I don’t know how accurate “ during “ parking is though. 
loosing the number 1 hydraulic system will also kill the nose and body gear steering so it would have required a tow in from the runway. Maybe they did tow her in and when the tug disconnected from the nose wheel that’s when it tipped back, but that should have been anticipated so I doubt that was the case.

It is reported as being empty of cargo but having fuel to fly to Germany, so due to the nature of the swept wing the C of G would be quite aft causing the tail to tip.

Again if the number 1 hydraulic was lost in flight they would have done an alternate nose/body gear extension( and deploy the flaps in the slower secondary electric mode)  , this is basically an electric motor powered by the number 4  electric bus which pulls out the up locks allowing the gear to free fall and lock into down. If the body gear didn’t lock down the crew would be aware of this and precautions to prevent a tail tip put in place.

The down locks are held in place by springs I believe so once they’re down even loosing hydraulics shouldn’t allow the gear to retract.

Its interesting to see the GPU cables are long enough to allow for this sort of thing without the GPU being pulled into the air.

On the flight deck when this sort of incident is imminent an early indication is the APU generators drop off line. What happens is as the nose wheel oleo starts to extend as the tail starts going down it triggers the air/ground logic sensor in the nose oleo and the aircraft thinks it’s airborne and trips the APU generators.

It will be interesting to learn what actually happened as more details emerge.

@psolk Paul on a separate subject I may need to PM you at a later date for some advice if you don’t mind. I’m about to buy a new sim rig and my 13 year old is salivating at the thought of getting my old PC for his motorsport simulation hobby, which is currently on the x-box. He’s talking about getting new wheel bases and other things I don’t understand .

Fascinating information, thank you as always!  I'd be curious to know how much time passed between landing, parking and the incident happening.  Was it immediate or a ticking time bomb (poor choice of words) type of thing where after sitting it finally lost enough hydraulic fluid and that was it.  They do say it left a significant amount of hydraulic fluid on the tarmac.

Feel free to PM on the racing sim, happy to help!   Just don't let him see any pictures of my setup or you will really be in trouble!   

[Andiroto 37]

Since the aircraft is in its parking position, a "Rear support frame" is usually placed under the tail for loading and unloading to prevent this!

[jon b 2,050]

Looking at the pictures it definitely seems like they ran the alternate gear extension.

How can you tell ?  Well with an alternate extension the gear doors open up as they are attached by mechanical linkages to the gear and the weight of the gear and airflow allows the gear to drop and the doors to open. However as there is no hydraulic power the gear doors are unable to close again like they would under a normal extension to reduce drag , so they remain fully open.

If you look at the pictures you can see the large nose wheel doors remain  open indicating a alternate extension ( I seem to remember PMDG had included this in their modelling if you want to experiment) The nose and body gear both use the same number 1 hydraulic system and use the same alternate gear extension switch, there’s a separate switch for the wing gear alt extension.

Though once again, there’s a sprung loaded down lock  clamp that should hold that body gear down even with no hydraulics so once it’s down it’s down.

If however it wasn’t indicating down the crew would have seen this and it would not have been taxied and as andiroto says a support frame and other precautions would have been put in place.

There’s more to this I feel , maybe something as simple as a language barrier not getting the full situation understood by the ground crew? I don’t know. 
That’s the thing when incidents like this happen and I’ve had a couple in my career, being the captain involved it’s equally annoying and amusing to read the  Internet speculation of what happened and what should have been done differently all speculation by people who haven’t got a clue of the facts of the situation.

It’s not like that here on avsim where we are just interested in understanding these events and how these machines work, unlike on some professional pilot forums , which I don’t actually frequent, which are always very quick to start pointing the finger.