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BALandorLivery
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A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 2:16 am

I would have thought that on such a long aircraft as the A340-600 airbus would have put in body gear steering to help around some of the sharper corners and narrower taxiways around.

A reliable source said that Virgin has/had an issue with this and uses the A340-300 to some destinations for this very reason. I don't know which destinations though.

Any thoughts?
 
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Richard28
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 3:04 am

Quoting BALandorLivery (Thread starter):
A reliable source said that Virgin has/had an issue with this and uses the A340-300 to some destinations for this very reason. I don't know which destinations though.

Could be some of their Caribbean destinations that require a 180 degree turn on the runway...
 
airfoilsguy
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 4:03 am

What is body gear steering? Do the main gear also steer?
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BALandorLivery
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 4:08 am

Ye, body gear steering is when the main wheels turn in the opposite direction to the nose wheel in order for the a/c to turn easier and tighter.

The only commercial aircraft I can think of that has it is the 747.
 
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 4:22 am

Quoting BALandorLivery (Reply 3):

I think the A380 also have it

Tom.
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Leezyjet
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 5:52 am

Quoting Richard28 (Reply 1):
Could be some of their Caribbean destinations that require a 180 degree turn on the runway...

The Airbus' don't fly to the Caribbean at all and don't operate to any destiantions from LGW.

Quoting BALandorLivery (Thread starter):
A reliable source said that Virgin has/had an issue with this and uses the A340-300 to some destinations for this very reason. I don't know which destinations though.

The only one I can think of is BOM, although the a/c has actually been there a few times - usually as a last minute swap with an A343. It is the stands that are the problem at BOM, they arenot big enough so the ac has to use 2 adjacent stands when it goes there.

IIRC the 346 has operated to every destination from LHR at some stage except SFO.

Quoting BALandorLivery (Thread starter):
I would have thought that on such a long aircraft as the A340-600 airbus would have put in body gear steering to help around some of the sharper corners and narrower taxiways around.

It would just add extra weight to the a/c and is another thing to maintain which = £££. If the a/c really needed it, Airbus would have fitted it. There are not that many turns that it can't make, and those are well documented for the flight crew and ATC, they may just have to taxi a little further at some places to another point where they can make the turn, so no big deal really.

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Richard28
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 6:13 am

Quoting Leezyjet (Reply 5):
Quoting Richard28 (Reply 1):
Could be some of their Caribbean destinations that require a 180 degree turn on the runway...

The Airbus' don't fly to the Caribbean at all and don't operate to any destiantions from LGW.

I thought I remembered reading that was one of the reasons why the 340's dont operate from LGW.

Can the A346 turn sharply enough to back track down a runway?
 
Geo772
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 6:24 am

Quoting AirbusA346 (Reply 4):
Quoting BALandorLivery (Reply 3):

I think the A380 also have it

Tom.

The 777 has main gear steering as well.
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aviopic
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 6:38 am

Quoting Airfoilsguy (Reply 2):
What is body gear steering? Do the main gear also steer?

Underneath a 74 the gears attached to the body are called the "body gear", the other set of wheels on the outside and attached to the wing structure is called "wing gear". Easy isn't it. Big grin
Only the body gear will assist the nose gear with steering though, the wing gear is fixed.

An example of steering a gear  Smile



The one in front is the 74 body gear and the taller one is the wing gear.


The A340 is eating it's tyres a bit and also it puts some extra strain on several parts which is why a certain Dutch company was requested to do more investigation and to come up with a solution a few years ago.
For this a special test rig was constructed.


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osiris30
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 6:41 am

Quoting Leezyjet (Reply 5):
The Airbus' don't fly to the Caribbean at all and don't operate to any destiantions from LGW.

I've seen Virgin's 340s in BGI. That would be the Caribbean :P
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PanAm747
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 6:48 am

I remember from an a.net post that South African has had serious issues with the A340-600 at Dakar, Senegal, because of the layout of the taxiways. IIRC, it was because the plane didn't steer well and the taxiways are a bit "tight".

http://gc.kls2.com/airport/DKR

Is this a situation unique to the -600 model?
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LTU932
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 7:02 am

Quoting Richard28 (Reply 6):
Can the A346 turn sharply enough to back track down a runway?

Technically yes. IB's A346 do it all the time here at SJO when they have to perform full runway rollouts or departures from 25.
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Morvious
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 7:35 am

You think that if an airliner buy some planes, they do some research of their caperbillitys. Ground manouvering etc is one of the things you need to know if you want top operate an aircraft to some destinations.

I also don't get it why the A346 (maybe 5 to) doesn't have body gear stearing. Maybe the extra weight was an issue for the plane?

Quoting Geo772 (Reply 7):
The 777 has main gear steering as well.

Yeah, but is it an option on the T7? Because I never noticed it IRL why I see it regular on the 747.

Also, is the whole gear stearing on the T7 or only the last 2 tires of each gear?
have a good day,

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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 8:57 am

Quoting Morvious (Reply 12):
Yeah, but is it an option on the T7? Because I never noticed it IRL why I see it regular on the 747.

Also, is the whole gear stearing on the T7 or only the last 2 tires of each gear?

Its standard and only the last two wheels on the 6 tire gear. The back section of the gear is hinged and the whole aft section of the gear truck turns side to side. It wont actually move unless the A/C is rolling. The actuator doesn't have enough umph to move the tires laterally. Its more to reduce scrubbing of the tires and reduce gear side loads. You can lock it out and fly with it on the MEL if it aint workin.
 
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Starlionblue
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 10:53 am

Quoting Geo772 (Reply 7):

The 777 has main gear steering as well.

As Pygmalion says, only the last axle in the bogies.

Quoting Aviopic (Reply 8):
An example of steering a gear

Priceless.
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jetmech
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 1:16 pm

Quoting Aviopic (Reply 8):
The one in front is the 74 body gear and the taller one is the wing gear.

Erm.... I think both of those landing gears are actually body landing gears. One is taller than the other probably because it has a larger charge of nitrogen in it.

http://i94.photobucket.com/albums/l118/Jet-Mech/IMG_0565.jpg

Main Landing Gear Steering (MLGS) helps to steer the plane as well as reducing torque loads through the Main Landing Gear (MLG) structure and the severity of tyre scrubbing.

It is probably needed for both of these reasons on the B777. The 3 axle MLG is so long that huge torque loads would be generated in the MLG structure along with severe tyre scrubbing if there was no steering facility.

A 2 axle MLG bogie still generates torque loads in the MLG structure as well as tyre scrubbing, but the severity of both is less due to the bogie being much shorter. If you look at the B747 from the side the Body Landing Gear (BLG) is actually located about 2 metres behind the Wing Landing Gear (WLG)*.

Due to this configuration, if the B747 did not have Body Gear Steering (BGS), there would be additional side and torque loads upon the B747 MLG when the plane performed a sharp turn. This is in addition to the torque loads already being imposed due to the bogie configuration. These massive torque and side loads are the critical issue, with a reduction in turn radius and tyre scrubbing as secondary issues.

IIRC, the Centre Landing Gear (CLG) on the A346 is located slightly behind the WLG's, so it may not suffer as much from the additional loads imposed on the B747 MLG. Of course, there will still be torque loads in the MLG structure as well as some tyre scrubbing, but I presume that Airbus was able to make the structure strong enough to accept these loads whilst still maintaining an acceptable turn radius without resorting to MLGS.

* The 2 metres is between the centrelines of the landing gear strut cylinders.

Regards, JetMech
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aviopic
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 4:21 pm

Quoting JetMech (Reply 15):
Erm.... I think both of those landing gears are actually body landing gears.

I am not a Boeing specialist or anything but that how we used to call them.
As said and as visible in your photo, one is underneath the body and the other underneath the wing.

Quoting JetMech (Reply 15):
One is taller than the other probably because it has a larger charge of nitrogen in it.

They are all filled with Nitrogen, at least as far as I know.
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 4:24 pm

Quoting Aviopic (Reply 8):
The one in front is the 74 body gear and the taller one is the wing gear.

Both are pictures of body gear. Why the strut is extended on the far one is beyond me.
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jetmech
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 04, 2006 4:45 pm

Quoting Aviopic (Reply 16):
They are all filled with Nitrogen, at least as far as I know.



Quoting Fr8Mech (Reply 17):
Why the strut is extended on the far one is beyond me.

That's right, the landing gear struts of a 747 are filled with nitrogen (as well as strut oil) but this level of nitrogen can be adjusted. The Body Landing Gear (BLG) in the fore-ground appears to have little or no nitrogen in it, whilst the BLG in the background appears to still contain an appreciable amount of nitrogen.

Quoting Fr8Mech (Reply 17):
Both are pictures of body gear.

Both of them are definitely BLG's. The 747 Wing Landing Gear has a completely different structure and the two are definitely not inter-changeable.
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kaddyuk
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RE: A340-600 Why No Body Gear Steering?

Sun Nov 05, 2006 2:14 am

Quoting JetMech (Reply 15):
Erm.... I think both of those landing gears are actually body landing gears. One is taller than the other probably because it has a larger charge of nitrogen in it.

Definatly body gear...

Quoting JetMech (Reply 18):
Both of them are definitely BLG's. The 747 Wing Landing Gear has a completely different structure and the two are definitely not inter-changeable.

And you can see the body gear steering pistons on both bogies...

Quoting Osiris30 (Reply 9):
I've seen Virgin's 340s in BGI. That would be the Caribbean :P

If you have, then you'd have seen the A343's

Quoting Richard28 (Reply 6):
I thought I remembered reading that was one of the reasons why the 340's dont operate from LGW.

Can the A346 turn sharply enough to back track down a runway?

The runway must be at least 55 meters across for the A346 to turn 180...

At airports such as ANU where the runway is only 45 meters wide, the airplane will clearly not be able to turn 180 and backtrack.
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LTU932
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RE: A340-600 Why No Body Gear Steering?

Sun Nov 05, 2006 7:06 am

Quoting Kaddyuk (Reply 19):
The runway must be at least 55 meters across for the A346 to turn 180...

At airports such as ANU where the runway is only 45 meters wide, the airplane will clearly not be able to turn 180 and backtrack.

Curious. This leads me to the question of why then the A346 is capable of making a 180 after backtracking at SJO. The runway is 3012x46 metres, or 9882x151 feet. Or is it simply possible for it because of the turning bay at the end of Runway 25's Displaced Threshold Area.

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Photo © Mario Villalobos

You can see here the turning bay to the right of the picture. The most curious part is that sometimes, they don't do the 180 counterclockwise, as is usual, but sometimes clockwise, especially after rollout.
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Leezyjet
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RE: A340-600 Why No Body Gear Steering?

Sun Nov 05, 2006 7:23 am

Quoting LTU932 (Reply 20):
Curious. This leads me to the question of why then the A346 is capable of making a 180 after backtracking at SJO. The runway is 3012x46 metres, or 9882x151 feet. Or is it simply possible for it because of the turning bay at the end of Runway 25's Displaced Threshold Area.



Quoting LTU932 (Reply 20):
You can see here the turning bay to the right of the picture. The most curious part is that sometimes, they don't do the 180 counterclockwise, as is usual, but sometimes clockwise, especially after rollout.

You answered your own question - the runway is clearly wider at the turing circle - which is the whole point in having it  Wink.

Quoting Osiris30 (Reply 9):
I've seen Virgin's 340s in BGI. That would be the Caribbean

Not recently you haven't, and as KaddyUK said, that would be an A343 not an A346  Wink

 Smile
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buckfifty
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RE: A340-600 Why No Body Gear Steering?

Sun Nov 05, 2006 3:40 pm

Quoting Kaddyuk (Reply 19):
The runway must be at least 55 meters across for the A346 to turn 180...

A343 Required Pavement Width for 180 turn = 51M / 166' @ 65 degree NWS angle

A346 Required Pavement Width for 180 turn = 59M / 193' @ 76 degree NWS angle
 
kaddyuk
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RE: A340-600 Why No Body Gear Steering?

Sun Nov 05, 2006 11:53 pm

Quoting BuckFifty (Reply 22):
A343 Required Pavement Width for 180 turn = 51M / 166' @ 65 degree NWS angle

A346 Required Pavement Width for 180 turn = 59M / 193' @ 76 degree NWS angle

Many Thanks... I knew it was around 55 Meters... Did try looking for the figure on the airbus website but wasnt really in the mood for scanning through pages of airport planning .pdf files...
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twal1011727
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RE: A340-600 Why No Body Gear Steering?

Mon Nov 06, 2006 2:03 am

Quoting AirbusA346 (Reply 4):
I think the A380 also have it

I have pictures of the A380 main gears tearing a taxiway to hell because they don't have body gear steering.

Airbus tried to save on weight by not installing it.

I'd love to post these pictures...but I'm not that adept at it.

KD
 
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Starlionblue
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RE: A340-600 Why No Body Gear Steering?

Mon Nov 06, 2006 4:53 am

Quoting TWAL1011727 (Reply 24):
I have pictures of the A380 main gears tearing a taxiway to hell because they don't have body gear steering.

Airbus tried to save on weight by not installing it.

Was this a test to see if they could get away without it?
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
RichardPrice
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RE: A340-600 Why No Body Gear Steering?

Mon Nov 06, 2006 5:34 am

Quoting TWAL1011727 (Reply 24):
I have pictures of the A380 main gears tearing a taxiway to hell because they don't have body gear steering.

Airbus tried to save on weight by not installing it.

I'd love to post these pictures...but I'm not that adept at it.

Would those by any chance be these ones:
http://img308.imageshack.us/img308/5465/tire33bn.jpg

Those photos are when they did mishandling tests on the A380 - they turned off main gear steering and deliberately turned the aircraft using a tug at a greater degree of turn than recommended.

Which resulted in the damage the the tarmac you have pictured.
 
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Starlionblue
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RE: A340-600 Why No Body Gear Steering?

Mon Nov 06, 2006 5:43 am

Quoting TWAL1011727 (Reply 24):

I'd love to post these pictures...but I'm not that adept at it.

Are they on the web? In that case simply paste the url between [img] and [/img] (no spaces). If they are not on the web mail me and I will send you details of an ftp to upload them to. I can put them on a website and post.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
twal1011727
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RE: A340-600 Why No Body Gear Steering?

Mon Nov 06, 2006 6:06 am

Quoting RichardPrice (Reply 26):
Would those by any chance be these ones:

Bingo....thx for the pix.....and to Starlionblue..thx..i'll give it a whirl someday..

KD
 
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jetmech
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RE: A340-600 Why No Body Gear Steering?

Mon Nov 06, 2006 8:36 am

Quoting RichardPrice (Reply 26):
Those photos are when they did mishandling tests on the A380 - they turned off main gear steering and deliberately turned the aircraft using a tug at a greater degree of turn than recommended.

Ouch  no ! That reminds me of a similar problem we had at my first employer. Our hangars were situated on the opposite side of the same taxiway used by the terminals.

When 747's were towed out of the hangar, they had to be towed at a maximum angle right hand turn as soon as the tail-fin was clear. That was bad enough on the Main Landing Gear (MLG) when Body Gear Steering (BGS) was available.

But as often is the case, the APU was not be functioning straight out of the "D" check, thus; this tortuous turn had to often be made without BGS. It was a testament to Boeing engineering that the Wing landing Gear (WLG) could absorb such side forces and torque - as evidenced by severe lateral bending of the entire WLG structure and twisting of the bogie beam as the wheels tried to tuck under - and not collapse. It was definitely one of those situations where you wanted to turn away but you kept on looking in sheer morbid fascination  faint .
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kaddyuk
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RE: A340-600 Why No Body Gear Steering?

Mon Nov 06, 2006 8:46 am

Quoting JetMech (Reply 29):
But as often is the case, the APU was not be functioning straight out of the "D" check, thus; this tortuous turn had to often be made without BGS. It was a testament to Boeing engineering that the Wing landing Gear (WLG) could absorb such side forces and torque - as evidenced by severe lateral bending of the entire WLG structure and twisting of the bogie beam as the wheels tried to tuck under - and not collapse. It was definitely one of those situations where you wanted to turn away but you kept on looking in sheer morbid fascination

I've seen the twist you get on the body and wing gear, once whilst attempting to troubleshoot a problem with the BGS system, we had to exceed the towing angle (under boeing approval). You really do see what the gear is made of when you do that...
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tangram
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RE: A340-600 Why No Body Gear Steering?

Tue Nov 07, 2006 7:32 am

I had the good fortune to fly in an SAA A340-600 London to Cape Town this summer. On our return to Heathrow we arrived early in the morning to a very busy airfield. We had to wait our turn in this huge aircraft close to Terminal 1 awaiting a gate to be freed up. I did wonder as we were parked, watching all the activity, how this leviathan would in fact place itself into such a tight spot. The gate now free we made the tightest right hand turn with such precision & ease which slotted us in perfectly. It was quite obvious to me at the time this is a pretty amazing aircraft! Why make the main gear complicated when what you have seems to be just the job.
 
kaddyuk
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RE: A340-600 Why No Body Gear Steering?

Tue Nov 07, 2006 9:57 am

Quoting Tangram (Reply 31):
Why make the main gear complicated when what you have seems to be just the job.

They can charge more money because the gear requires more maintenance if its complicated...!
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CF188A
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RE: A340-600 Why No Body Gear Steering?

Mon Nov 13, 2006 2:45 am

Are there any photos on A.NET which clearly show the 747 body gear in action (slightly pivoted) ... if anyone can find a photo please show .. thanks
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Starlionblue
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RE: A340-600 Why No Body Gear Steering?

Mon Nov 13, 2006 2:49 am

Quoting CF188A (Reply 33):
Are there any photos on A.NET which clearly show the 747 body gear in action (slightly pivoted) ... if anyone can find a photo please show .. thanks


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Photo © Erwin



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Photo © Aaron Liu
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CF188A
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RE: A340-600 Why No Body Gear Steering?

Mon Nov 13, 2006 2:51 am

THANKS ALOT.... quickest response ever lol
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Tristarsteve
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RE: A340-600 Why No Body Gear Steering?

Mon Nov 13, 2006 3:47 am

Quoting Morvious (Reply 12):
Yeah, but is it an option on the T7? Because I never noticed it IRL why I see it regular on the 747.

I dont think you will ever notice it turning. I watch a B777 every day do the 90deg turn out of the bay on pushback, from the pushback tug, and I can't see it. I know it works because you can see it moving on the maint pages in the flight deck as you tow it.
 
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Starlionblue
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RE: A340-600 Why No Body Gear Steering?

Mon Nov 13, 2006 9:40 am

Quoting CF188A (Reply 35):
THANKS ALOT.... quickest response ever lol

We aim to please but mostly it was just lucky timing. Big grin
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SP90
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RE: A340-600 Why No Body Gear Steering?

Sat Nov 18, 2006 11:37 pm

Here is something I came up with a while ago.

Big version: Width: 288 Height: 437 File size: 12kb


Does the MLG on the really big transports (C-5 and AN-224?) steer at all?
 
Curmudgeon
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RE: A340-600 Why No Body Gear Steering?

Sun Nov 19, 2006 7:26 am

Quoting JetMech (Reply 29):


When 747's were towed out of the hangar, they had to be towed at a maximum angle right hand turn as soon as the tail-fin was clear. That was bad enough on the Main Landing Gear (MLG) when Body Gear Steering (BGS) was available.

But as often is the case, the APU was not be functioning straight out of the "D" check, thus; this tortuous turn had to often be made without BGS. It was a testament to Boeing engineering that the Wing landing Gear (WLG) could absorb such side forces and torque - as evidenced by severe lateral bending of the entire WLG structure and twisting of the bogie beam as the wheels tried to tuck under - and not collapse. It was definitely one of those situations where you wanted to turn away but you kept on looking in sheer morbid fascination

Was that ever implicated in the 743 strut failure in Rome a few years ago? I am always impressed by the torque load on those inner struts when a max effort turn is being made, and recall at least one other widebody strut failure as the aircraft (DC-10) was being alligned for take-off.
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jetmech
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RE: A340-600 Why No Body Gear Steering?

Mon Nov 20, 2006 3:56 pm

Quoting Curmudgeon (Reply 39):
Was that ever implicated in the 743 strut failure in Rome a few years ago?

Good question, I couldn't find any information as to the cause of that failure. I'm sure that Boeing calculated for the steepest turn scenario at MTOW with BGS, and that this may have been the limiting load case for torsional stress in the landing gear leg.

I would presume that some pre-existing, undetected defect was the cause of the failure. I presume that this sort of turn could still be made if BGS failed through the turn, but it would be highly likely to be a no go if you knew that the BGS was unavailable beforehand.

The inspection job to detect cracks and pre-existing defects in this area was very tedious. To gain access to the area, you had to lower the flaps and use a high lift platform or stand.

Because of the upper and lower fixed trailing edge panels in the area, you then had to lean your body forward with your arms fully outstretched into a space that was only about a foot high. The rear spherical trunnion of the WLG was about two feet from the end of the fixed trailing edge panels.

From this position, you were expected to be able to clean the inside of the WLG structure of all grease and dirt. Of course, the diameter of the inside of the WLG was just small enough that you couldn't get your hand inside. Thus, you had to use rags on the end of wooden sticks to clean inside the WLG structure.

Provided you managed to get all the grease and dirt out, you were then expected to use a mirror and torch and detect hairline cracks and casting defects the size of a grain of sand from a distance of about three feet in front of your face. You then had to repeat for the other side  faint !
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
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Starlionblue
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RE: A340-600 Why No Body Gear Steering?

Mon Nov 20, 2006 8:57 pm

Quoting JetMech (Reply 40):
From this position, you were expected to be able to clean the inside of the WLG structure of all grease and dirt. Of course, the diameter of the inside of the WLG was just small enough that you couldn't get your hand inside. Thus, you had to use rags on the end of wooden sticks to clean inside the WLG structure.

Provided you managed to get all the grease and dirt out, you were then expected to use a mirror and torch and detect hairline cracks and casting defects the size of a grain of sand from a distance of about three feet in front of your face.

Wow! This is when you wonder when those microrobot designers will make a product for you. Have it crawl in whole you sit comfortably by a monitor.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Mr.BA
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Joined: Sun Sep 24, 2000 12:26 pm

RE: A340-600 Why No Body Gear Steering?

Tue Nov 21, 2006 2:13 pm

I vaguely remember that in the B747 classics one the pilot has to turn off the body gear steering before advancing the throttles for takeoff.. why is this so? Or did I recall wrongly? Thanks!
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