BA A380 Lands With A Square Tire

zkojq · Mon May 09, 2016 7:45 am

From AvHerald:

Quote:
A British Airways Airbus A380-800, registration G-XLEB performing flight BA-32 from Hong Kong (China) to London Heathrow,EN (UK), was climbing out of Hong Kong close to reaching the top of climb when the crew received a tyre pressure indication. The crew decided to continue the flight to London and requested a tow tug to be available for landing in case the aircraft would not be able to taxi on its own. The aircraft landed safely on Heathrow's runway 09L and taxied to the gate.

The aft right outboard body tyre caused a lot of head scratching trying to explain how the stunning square shape of the damaged tyre came together (editorial note: the original of the photo does not exhibit any indication of photoshopping).

http://avherald.com/h?article=498050d8&opt=0

I checked and its not April 1st.

Someone83 · Mon May 09, 2016 8:01 am

There is something odd with the photo. Look at the rim in the square wheel vs the round one. There is another type of rim, which AFAIK should be the same? Or am I wrong?

moo · Mon May 09, 2016 8:18 am

Quoting Someone83 (Reply 2):
There is something odd with the photo. Look at the rim in the square wheel vs the round one. There is another type of rim, which AFAIK should be the same? Or am I wrong?

I have no idea whether this answers your question or not, but on the fuselage main gear, not all wheels are braking and the rear pair are steering, resulting in different rims.

https://www.airliners.net/photo/1237902/M/

Quoting Heavierthanair (Reply 1):
Maybe not a Photoshop, but definitely not an A 380 wheel. The wheel rim and number of bolts/nuts are different on the square wheel, so someone "manufactured" a little joke here

Looking at the above photo, looks like a real photo to me!

FCAFLYBOY · Mon May 09, 2016 8:22 am

Looks legit! Hopefully someone has already tweeted BA to ask the obvious question.

speedbored · Mon May 09, 2016 8:23 am

Quoting Heavierthanair (Reply 1):
Maybe not a Photoshop, but definitely not an A 380 wheel. The wheel rim and number of bolts/nuts are different on the square wheel, so someone "manufactured" a little joke here

I wouldn't be so sure of that - some of the hubs do appear to be different on the A380. Probably due to not every wheel being equipped with brakes:

My guess is that, during the flight, the internal tyre pressure completely equalised with the low cruise altitude atmospheric pressure and, during descent, the increasing external pressure caused the buckling as the sides of the tyre were pushed inwards by the increasing pressure. Odd that it should end up so symmetrical though.

TFFIP · Mon May 09, 2016 8:42 am

VV701 is needed here....

Heavierthanair · Mon May 09, 2016 8:44 am

G'day

Quoting speedbored (Reply 5):
some of the hubs do appear to be different on the A380

I stand corrected!

That pic proofs different wheel designs are being used. Your theory on how that square buckling occurred also makes sense. Learned something new today

Cheers

Peter

N14AZ · Mon May 09, 2016 8:45 am

Quoting zkojq (Thread starter):
I checked and its not April 1st.

Ahh, THAT's what they call British (Airways) humour....

David L · Mon May 09, 2016 9:20 am

Quoting zkojq (Thread starter):
The aft right outboard body tyre caused a lot of head scratching trying to explain how the stunning square shape of the damaged tyre came together

South Park has the answer, eh?

zeke · Mon May 09, 2016 9:41 am

Quoting zkojq (Thread starter):

I would suggest what has happened is the tyre did leak during the climb and in cruise and equalized over the flight to near the cruise altitude pressure. During descent as the outside pressure increased the tyre is being reshaped into its current form by atmospheric pressure.

If I put the lid on an empty 1.5 liter plastic water bottle in cruise, when I get on the ground the higher atmospheric pressure will partially collapse the bottle like this so that the pressure inside is close to equal to the atmosphere.

uta999 · Mon May 09, 2016 10:21 am

Was it a Chinese direct replacement tyre ordered through eBay?

starbucks · Mon May 09, 2016 10:44 am

Quoting zeke (Reply 11):

This indeed, same goes up for your ears during climb and descend...

During climb the outside pressure drops and air from your "middle ear" (area between eardrum and the inner ear/"snailhouse) flows out easily via the pressure equalizing tube (for most of the earparts I do not know the correct English term, so I translated from Dutch, I hope it is clear enough

)

When descending the air has to come back in, this is more difficult and happens at a slower rateresulting in a pressure difference on the eardrum causing a slight discomfort, this is why flying with a cold is usually discouraged, the pressure equalizing tube is blocked resuling in more pressure difference and more discomfort or even pain.

I expect the same happened with the tire, during cruise all the nitrogen leaked out of the tire untill the pressures equalized, when they started descending the increased in outside pressure was greater than the rate air could flow back into the tire causing it to collapse on itsself.

nitepilot79 · Mon May 09, 2016 11:37 am

In my defense, I did type "An-225" not "AN-225" in the 2016 April Fool's thread, though

. I'll digress now.

ba9216c · Mon May 09, 2016 11:51 am

The rear body landing gear wheels on the A380 are certainly different. They use a solid Hub rather than a vented one since no brakes are fitted here.

Is this not a similar incident to the Air India 777 a few weeks ago?

nitepilot79 · Mon May 09, 2016 12:10 pm

Quoting ba9216c (Reply 14):
Is this not a similar incident to the Air India 777 a few weeks ago?

A link, perhaps? I searched google just now, and couldn't find anything ...

nitepilot79 · Mon May 09, 2016 12:11 pm

Not saying you aren't correct

.

Erebus · Mon May 09, 2016 2:47 pm

Quoting ba9216c (Reply 14):
The rear body landing gear wheels on the A380 are certainly different.

The last pair of wheels on the body landing gear also assist in steering.

View Large View Medium
Click here for bigger photo!

Photo © Lars Hentschel

View Large View Medium
Click here for bigger photo!

Photo © Lars Hentschel

D L X · Mon May 09, 2016 4:11 pm

Quoting David L (Reply 9):
South Park has the answer, eh?

Maybe not, but Tom Brady probably does!

PV=nRT is always the answer.

Amiga500 · Mon May 09, 2016 4:14 pm

Not that surprising really.

No-one here ever seen a buckled stiffened panel?

http://aerospaceengineeringblog.com/...ntent/uploads/2012/08/Untitled.png

JohnGalt · Mon May 09, 2016 5:30 pm

Quoting Erebus (Reply 17):
The last pair of wheels on the body landing gear also assist in steering.

Wow! The loads on the right (left as you view the photo) landing gear and tires are impressive! View the large versions of these photos if you haven't already.

jetlag73 · Mon May 09, 2016 5:40 pm

I was on that flight last Friday, landed LHR on May 6th at 5:50AM from HKG.
Once landed, we saw quite a lot of safety and fire trucks around our A380.
Then the captain told us not to be alarmed by the show around us, and informed us about a "deflated" tire. He sid that we shouldn't worry as the A380 has 22 tires.
He then said the taxi to the gate will be very slow for safety reason. We got to the gate fine, but all those trucks followed us all the way, quite funny.
Got a pick on my phone, sorry for the poor quality.
Cheers to the captain and crew.

D L X · Mon May 09, 2016 7:24 pm

Was the deflated tire in contact with the ground when the plane taxied?

How long does it take to inflate a tire to the point that it would roll? Could that have been done with the passengers on board? (Would that have saved any time?)

Quoting jetlag73 (Reply 21):
He then said the taxi to the gate will be very slow for safety reason.

How long did it take you to get to the gate? Was it noticeably longer?

atypical · Mon May 09, 2016 9:06 pm

Quoting D L X (Reply 22):
Was the deflated tire in contact with the ground when the plane taxied?

How long does it take to inflate a tire to the point that it would roll? Could that have been done with the passengers on board? (Would that have saved any time?)

The picture shows it is not making any contact with the ground. Should be good to taxi.

It looks like a significant leak that at cruise normalized to outside pressure. On descent the leak couldn't normalize pressure anywhere near fast enough and collapsed. Unless the ground responders had a good 40-50 bottles of fix-a-flat they will need to replace it anyway. If it does make some incidental contact on the way in it won't break anything or matter very much.

peterinlisbon · Mon May 09, 2016 9:27 pm

I have another theory - maybe Airbus just forgot to make the tyre round.

prebennorholm · Mon May 09, 2016 11:35 pm

Is there something about Heathrow and square wheels?

Fifteen years ago I rented a Toyota at Heathrow. It also had square wheels. Made my own old VW feel like a magic flying carpet.

AWACSooner · Tue May 10, 2016 1:20 am

Who let the South Park Canadians change the tire on that A380?

sturmovik · Tue May 10, 2016 1:23 am

I vote we rename the aircraft as SpongeBob SquareWheels.

ish2dachoppa · Tue May 10, 2016 2:52 am

If I remember correctly from my tech school days, wont the tire across from it on the same axle also have to be replaced due to higher than normal stresses?

gkirk · Tue May 10, 2016 8:51 am

Quoting sturmovik (Reply 27):

Or Planey McSquareWheels

SKAirbus · Tue May 10, 2016 10:05 am

Planey McPlaneFace. Surely an airline has to name one of their aircraft this? WOW Air maybe?

tonystan · Tue May 10, 2016 10:31 am

Quoting SKAirbus (Reply 30):

Suggest you google search Aer Lingus PlaneyMcplaneface

jetlag73 · Tue May 10, 2016 5:27 pm

Quoting D L X (Reply 21):

How long did it take you to get to the gate? Was it noticeably longer?

I would says about twice longer than usual

gatibosgru · Tue May 10, 2016 6:04 pm

Quoting SKAirbus (Reply 29):
Planey McPlaneFace.

http://twitter.com/AerLingus/status/722162956319002625

[Edited 2016-05-10 11:05:02]

ba9216c · Tue May 10, 2016 8:47 pm

Quoting nitepilot79 (Reply 14):

Indeed took me a while to find also. Found it on Twitter.

Quoting Ish2dachoppa (Reply 27):

You are correct. There are certain conditions depending on if the aircraft has been taxied / towed on a deflated tyre and what the deflation pressure was. On this occasion a full deflation will definitely result in a double wheel change on the axle.

SelseyBill · Tue May 10, 2016 10:41 pm

Quoting D L X (Reply 17):
Maybe not, but Tom Brady probably does!

Just reaching for my copy of 'The Wells Report' to read all about the 'ideal gas law', as I read your post.

I think the maintenance crews at LHR, "more probably than not" know they have a problem with that 380 wheelset.......

afriwing · Wed May 11, 2016 1:41 pm

Quoting zeke (Reply 9):
I would suggest what has happened is the tyre did leak during the climb and in cruise and equalized over the flight to near the cruise altitude pressure. During descent as the outside pressure increased the tyre is being reshaped into its current form by atmospheric pressure.

That makes perfect sense. But I still can't get my head around why does it collapse to a square shape, why so symmetrical? I'd expect a randomly shaped deflated tyre.

Like in this example:

Quoting zeke (Reply 9):
If I put the lid on an empty 1.5 liter plastic water bottle in cruise, when I get on the ground the higher atmospheric pressure will partially collapse the bottle like this so that the pressure inside is close to equal to the atmosphere.

One would expect the bottle to collapse and crumble into a random shape, not turn into a smaller rectangular bottle, right? I'm still baffled. Anyone kindly explain why the symmetry?

SKAirbus · Wed May 11, 2016 2:06 pm

Hmm could the square shape be due to the taxi from the runway to the terminal? If it was deflated then it will likely have "morphed" into a square shape when moving towards the gate.

flipdewaf · Wed May 11, 2016 2:29 pm

Quoting afriwing (Reply 35):
That makes perfect sense. But I still can't get my head around why does it collapse to a square shape, why so symmetrical? I'd expect a randomly shaped deflated tyre.

My stab at explaining it. The pressure differential of 75kpa+ makes the forces due to gravity (the weight of the rubber) negligible in comparison to the forces due to the pressure differential. The tyre is a very uniform shape (Taurus) with a very uniform strength/stiffness and it to all intents and purposes being acted on by a uniform force then one would expect to find a very uniform shape. Any uniform shape that is set up is likely to do with the strength of the sidewall and the size of the tyre relative to the rim in that it will set up a series of nodes, in this instance it is 4. I would wager that the A380 tyre will always look like this if there is a leak in flight. I imagine if there was a lower profile tyre (lower sidewall height) there will be a point at which the number of nodes reaches 5.

Quoting afriwing (Reply 35):
One would expect the bottle to collapse and crumble into a random shape, not turn into a smaller rectangular bottle, right? I'm still baffled. Anyone kindly explain why the symmetry?

Bottle has not supporting structure (wheel) is a much less uniform shape so pressure forces act differently in different areas, the bottle has a less uniform strength.

Fred

PW100 · Wed May 11, 2016 3:38 pm

Quoting afriwing (Reply 35):
That makes perfect sense. But I still can't get my head around why does it collapse to a square shape, why so symmetrical? I'd expect a randomly shaped deflated tyre.

Well, it can't go into a perfectly round shape: since all that tyre material is pushed inwards by the higher outside pressure, compression stresses are introduced in the tyre. And rubber can handle compression stresses, so it will buckle at some/several point(s). The round shape (closed circle) will guarantee some sort of symmetrical shape. The question why is is square, rather than triangular, or hexagonal, is more difficult to answer. I guess it is probably related to the dynamic characteristics of the design shape in combination with material properties.

Concorde tyre wanted to go into triangular shape . . . :
[shameless self-plug]

View Large View Medium
Click here for bigger photo!

afriwing · Thu May 12, 2016 1:00 am

Quoting flipdewaf (Reply 37):
The tyre is a very uniform shape (Taurus) with a very uniform strength/stiffness

Agreed, but that's in case of a brand new tyre. But after going through numerous landings the tyre wall thickness changes randomly. I've seen tyres that almost lost their grooves at one location and have perfect grooves in other locations. For these "normal conditions" I'd expect the majority of the deformed walls to be where the tyre is thinnest.

Quoting SKAirbus (Reply 36):
I would wager that the A380 tyre will always look like this if there is a leak in flight

And if the leak was due to some minute defect in the tyre rubber or where the rubber meets the steel rim then that area of weakness should bear the most deformation.

Quoting PW100 (Reply 38):
The round shape (closed circle) will guarantee some sort of symmetrical shape

Agree too

Quoting PW100 (Reply 38):
Concorde tyre wanted to go into triangular shape . . .

A332DTW · Thu May 12, 2016 2:10 am

Quoting Erebus (Reply 16):
The last pair of wheels on the body landing gear also assist in steering.

Interesting, never knew that about the A380. Always neat to learn something new about a particular aircraft. The main gear wheels turn in the opposite direction of the turn. Not your typical steering system.

Erebus · Thu May 12, 2016 2:39 am

Quoting A332DTW (Reply 40):
Interesting, never knew that about the A380.

A similar function also exists on the 777's MLG. Very subtle in the following video.

http://www.youtube.com/watch?v=nCesQyVf-M0

77west · Thu May 12, 2016 4:06 am

Quoting A332DTW (Reply 40):
Quoting Erebus (Reply 16):The last pair of wheels on the body landing gear also assist in steering.
Interesting, never knew that about the A380. Always neat to learn something new about a particular aircraft. The main gear wheels turn in the opposite direction of the turn. Not your typical steering system.

Quoting Erebus (Reply 41):

A similar function also exists on the 777's MLG. Very subtle in the following video.

http://www.youtube.com/watch?v=nCesQyVf-M0

The 747 pioneered this, where both entire body gear assemblies can assist in steering "body gear steering"

The 777-300 -300ER and A380 introduced axle-only steering on the rear axles of the 3-axle assemblies.

Helps to tighten the turn and reduce tire scrubbing.

I believe it is allowed to be deactivated and locked out if need be, with precautions taken, for normal ops.

litz · Thu May 12, 2016 6:05 pm

That picture should be a featured lecture in every secondary school physics class when discussing gasses and pressure.

ish2dachoppa · Fri May 13, 2016 5:29 am

Quoting 77west (Reply 42):
The 747 pioneered this, where both entire body gear assemblies can assist in steering "body gear steering"

For commercial airliners sure, but the C-5 had the same feature and flew 8 months before the 747 did:

Who is online

Popular Searches On Airliners.net