Oasis
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Middle Landing Gear On Airbus 340

Wed Jun 11, 2008 5:36 am

Hi
I was wondering what would happen to an A340-200/300 if the middle gear (the one under in between the wings) would be removed (if that is even possible to just have it be removed?) Would the middle part of the fuselage collapse? Because the only difference between an A330-300 and an A340-200/300 is that one has 4 engines, and the A330 doesn't have any gear in the middle. Is it a weight issue? I think I remember seeing a picture of a CX A340 at Kai Tak without the middle gear.

I hope that made sense :P

-Ben
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wilco737
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RE: Middle Landing Gear On Airbus 340

Wed Jun 11, 2008 5:44 am



Quoting Oasis (Thread starter):

Hi,

I guess this thread should be in Tech/ Ops.

I am not 100% sure for the A340. But for the MD11 you can remove the center landing gear as well. Or let it be retracted. Nothing would collaps but you have a huge reduction in the maximum weights. The MTOW reduces to 220 tons instead of 286 tons. Same for the landing weight. But I don't know the figures there.
So I bet it is possible for the 340 as well. And nothing would collapse.

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vikkyvik
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RE: Middle Landing Gear On Airbus 340

Wed Jun 11, 2008 6:25 am



Quoting WILCO737 (Reply 1):

I am not 100% sure for the A340. But for the MD11 you can remove the center landing gear as well. Or let it be retracted. Nothing would collaps but you have a huge reduction in the maximum weights. The MTOW reduces to 220 tons instead of 286 tons. Same for the landing weight. But I don't know the figures there.
So I bet it is possible for the 340 as well. And nothing would collapse.

Hey WILCO, is it on the MD-11 that the center gear is non-load bearing at lighter weights? As in, it'll actually be off the ground?

I'm pretty sure that's the case for EITHER the MD-11 or the A340....but I don't remember which one.

However, there have been cases when the center gear is inoperable for some reason. The airplane can still fly (I guess the center gear gets MEL'd?), but I'd think the weights are reduced, as Phil said.

Here we go, found one:


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Photo © Mark McWhirter - Contrails Aviation Photography



There used to be a photo with a Cathay Pacific 340 at Kai Tak....but couldn't find that one.
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buckfifty
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RE: Middle Landing Gear On Airbus 340

Wed Jun 11, 2008 6:27 am



Quoting Oasis (Thread starter):
Hi
I was wondering what would happen to an A340-200/300 if the middle gear (the one under in between the wings) would be removed (if that is even possible to just have it be removed?) Would the middle part of the fuselage collapse? Because the only difference between an A330-300 and an A340-200/300 is that one has 4 engines, and the A330 doesn't have any gear in the middle. Is it a weight issue? I think I remember seeing a picture of a CX A340 at Kai Tak without the middle gear.

The middle gear itself can be stowed in the uplocked position, with a reduced Max Ramp Weight / Max Takeoff Weight. Otherwise it has no effect at all on the Max Landing Weight. In effect, without the centre gear, the weights which the A340 operate at are more or less those of a maxed out A330. However, this obviously depends on what configurations / standard either aircraft are built to when you do the comparison.

The centre gear itself is not a landing load bearing gear. Therefore, if we had a main gear stuck in the stowed position, we must land without the centre gear in order not to damage the fuselage. The only way to do that is via a gravity extension.
 
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Starlionblue
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RE: Middle Landing Gear On Airbus 340

Wed Jun 11, 2008 6:27 am

Definitely a weight issue. The 340 is designed for longer haul flights with higher weights.

You can probably retract it for maintenance purposes. As Wilco737 points out the MD11 can have it MELd. I believe it was MD11Engineer who posted the checklist for such an event, ending with "inform the pilots of the coming weight and balance nightmare".  Wink
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WingedMigrator
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RE: Middle Landing Gear On Airbus 340

Wed Jun 11, 2008 6:31 am



Quoting Buckfifty (Reply 3):
The centre gear itself is not a landing load bearing gear.

What else is its function then-- ornamentation?

Or is it something having to do with the bearing capacity of aprons and taxiways?
 
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RE: Middle Landing Gear On Airbus 340

Wed Jun 11, 2008 6:39 am



Quoting WingedMigrator (Reply 5):
Or is it something having to do with the bearing capacity of aprons and taxiways?

As far as I understand it, yes.
 
wilco737
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RE: Middle Landing Gear On Airbus 340

Wed Jun 11, 2008 6:44 am



Quoting Vikkyvik (Reply 2):
Hey WILCO, is it on the MD-11 that the center gear is non-load bearing at lighter weights? As in, it'll actually be off the ground?

As far as I know, it has always contact to the ground. Even at lighter weight. I think it was the 340 where it is "airborne" when empty.

Quoting Starlionblue (Reply 4):
As Wilco737 points out the MD11 can have it MELd. I believe it was MD11Engineer who posted the checklist for such an event, ending with "inform the pilots of the coming weight and balance nightmare". Wink

Oh yeah, the weight and balance nightmare. For us cargo it doesn't make any sense to fly without that gear. You cannot take much load with you then. So, better get a new one first  Wink

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Mir
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RE: Middle Landing Gear On Airbus 340

Wed Jun 11, 2008 9:07 am



Quoting WingedMigrator (Reply 5):
Or is it something having to do with the bearing capacity of aprons and taxiways?

Precisely. Only eight main wheels puts too much load on each for the taxiways to bear. Thus the 340 has ten. The 340NG and 777 have twelve (though the 777 has no center gear). You can go without the center gear on the 340 or MD11, but you're going to be weight restricted so as to not exceed taxiway strength limits.

Until recently, 777-300s and 340-600s couldn't use the taxiway bridges at JFK due to the fact that despite the extra wheels, they still have very high pavement loading, more than what the bridges could withstand. The bridges have since been rebuilt and now there are no restrictions.

-Mir
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BA777
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RE: Middle Landing Gear On Airbus 340

Wed Jun 11, 2008 10:23 am

Yep it has to do with the ACN and PCN numbers as mentioned by Mir  Smile
 
Tristarsteve
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RE: Middle Landing Gear On Airbus 340

Wed Jun 11, 2008 10:23 am

An engineer friend of mine was working in Sanaa on the BA DC10 when it was a scheduled flight there. I think it was the last flight, anyway he had no spare mainwheel, and needed to change a wing gear wheel. So they removed a S wheel from the centre gear and fitted it on the wing posn, then retracted the centre gear and flew the aircraft back to LGW.
 
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HAWK21M
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RE: Middle Landing Gear On Airbus 340

Wed Jun 11, 2008 11:49 am



Quoting Tristarsteve (Reply 10):
An engineer friend of mine was working in Sanaa on the BA DC10 when it was a scheduled flight there. I think it was the last flight, anyway he had no spare mainwheel, and needed to change a wing gear wheel. So they removed a S wheel from the centre gear and fitted it on the wing posn, then retracted the centre gear and flew the aircraft back to LGW.

Interesting.Reminds me of the MEL move on B752 using the serviceable secondary EICAS display on the u/s EHSI position
 Smile
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Oasis
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RE: Middle Landing Gear On Airbus 340

Wed Jun 11, 2008 10:58 pm

thanks for the help guys  Smile and sorry about posting in the wrong forum
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flynavy
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RE: Middle Landing Gear On Airbus 340

Wed Jun 11, 2008 11:16 pm



Quoting Buckfifty (Reply 3):
The centre gear itself is not a landing load bearing gear.

 checkmark  This photo clearly shows this:
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Photo © Tango3 - Team Ninervictor

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SlamClick
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RE: Middle Landing Gear On Airbus 340

Wed Jun 11, 2008 11:54 pm



Quoting WingedMigrator (Reply 5):
is it something having to do with the bearing capacity of aprons and taxiways?



Quoting Buckfifty (Reply 6):
As far as I understand it, yes.

For sure, here in the US, load bearing capacity for airports is driven by wheel configuration.

However, I always assumed, from the placement, that it was specifially increase max zero-fuel weight including weight from centerline tanks which, structurally, behaves like payload.
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askr
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RE: Middle Landing Gear On Airbus 340

Thu Jun 12, 2008 9:07 am

There is a pic in the database of a Varig MD11 or DC-10, cant recall, where the middle landing gear... fell off. Well, at least the bogey.

Maybe MD11 will have a pic of that somewhare  Smile
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buckfifty
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RE: Middle Landing Gear On Airbus 340

Thu Jun 12, 2008 7:47 pm



Quoting SlamClick (Reply 14):
However, I always assumed, from the placement, that it was specifially increase max zero-fuel weight including weight from centerline tanks which, structurally, behaves like payload.

The 333 and 343 both have very similar MZFW's. And without the centre gear down, the 343 is limited to a MTOW which is, again, similar to that of a 333.

With the MLW virtually the same for both aircraft, one would assume that the centreline gear is indeed there to increase the MTOW / MRW, by increasing the footprint for a lower ACN.

The centre tank on the 340, incidentally, is an integral tank in the wingbox, which is different than the pallet loaded ACT. Not sure if anyone uses those anymore...
 
askr
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RE: Middle Landing Gear On Airbus 340

Thu Jun 12, 2008 8:01 pm



Quoting Askr (Reply 15):
There is a pic in the database of a Varig MD11 or DC-10, cant recall, where the middle landing gear... fell off. Well, at least the bogey.

Maybe MD11 will have a pic of that somewhare

Damn, it was supposed to be WILCO737  Wink
Sorry for the mixup  Wink
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vikkyvik
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RE: Middle Landing Gear On Airbus 340

Thu Jun 12, 2008 9:21 pm



Quoting WILCO737 (Reply 7):
As far as I know, it has always contact to the ground. Even at lighter weight. I think it was the 340 where it is "airborne" when empty.

OK, that's what I thought. Thanks.

Quoting Askr (Reply 17):
Damn, it was supposed to be WILCO737

That's his fault for switching aircraft on us  Wink
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wilco737
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RE: Middle Landing Gear On Airbus 340

Fri Jun 13, 2008 4:50 am



Quoting Askr (Reply 17):
Damn, it was supposed to be WILCO737 Wink

 rofl   Wink

No, I don't have a pic of it without the center gear.

Quoting Vikkyvik (Reply 18):
That's his fault for switching aircraft on us Wink

Won't happen for enother 2 more years  Wink hehe

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Airbus_A340
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RE: Middle Landing Gear On Airbus 340

Fri Jun 13, 2008 7:07 pm

Something you might find interesting, when unloaded, the A340 centre landing gear doesn't touch the ground, it hangs a couple of inches off the ground, until loading/refuelling.
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askr
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RE: Middle Landing Gear On Airbus 340

Fri Jun 13, 2008 10:17 pm

Found it


View Large View Medium
Click here for bigger photo!

Photo © Allan K. B. Ramos


Now I wonder what sort of red stuff on the control panel this incident brought...



[Edited 2008-06-13 15:20:56]
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Viscount724
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RE: Middle Landing Gear On Airbus 340

Sun Jun 15, 2008 1:02 am



Quoting WILCO737 (Reply 1):
But for the MD11 you can remove the center landing gear as well. Or let it be retracted. Nothing would collaps but you have a huge reduction in the maximum weights.

Reminds me of the following incident involving a World Airways MD-11F departing ANC on a 2-engine ferry flight with the center landing gear retracted.
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20041020X01664&key=1

Longer version:
http://www.ntsb.gov/ntsb/brief2.asp?...020X01664&ntsbno=ANC05IA002&akey=1
 
wilco737
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RE: Middle Landing Gear On Airbus 340

Sun Jun 15, 2008 6:21 am



Quoting Viscount724 (Reply 22):
Reminds me of the following incident involving a World Airways MD-11F departing ANC on a 2-engine ferry flight with the center landing gear retracted.
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20041020X01664&key=1

Longer version:
http://www.ntsb.gov/ntsb/brief2.asp?...key=1

Oops, something went wrong here  Wink

Thanks for the links, never heard of that incident.

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RE: Middle Landing Gear On Airbus 340

Sun Jun 15, 2008 2:49 pm



Quoting WILCO737 (Reply 23):
Oops, something went wrong here

I'm only imaging the language in the cockpit. Can you imagine? You apply TO thrust and suddenly you're rotating without having moved anywhere?
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