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A320 Nose Gear Retraction  
User currently offlineMeister808 From United States of America, joined Jan 2000, 973 posts, RR: 1
Posted (7 years 6 months 4 days 15 hours ago) and read 6424 times:

Ok folks, I guarantee this has been discussed before, but I can't find it - does the A320 family nosewheel turn 90° on retraction into the nose wheel well, or does it go straight forward? I can't seem to find anything that would suggest that it turns, but the topic came up in discussion and there's more than a few people I know that insist such a design was the reason for the well-publicized Jetblue incident at LAX last year.

Am I missing something?

-Meister

[Edited 2007-04-24 23:19:05]


Twin Cessna 812 Victor, Minneapolis Center, we observe your operation in the immediate vicinity of extreme precipitation
29 replies: All unread, showing first 25:
 
User currently offlineB78710 From United Kingdom, joined Mar 2006, 343 posts, RR: 0
Reply 1, posted (7 years 6 months 4 days 15 hours ago) and read 6421 times:

most nose gear have whats called a centering cam which ensures the nose gear is straight before retraction, if it isn't it will not retract! the gear probably wouldnt even fit into the bay if it was at 90 degree's.....but dont quite me on that!

wasn't the jet blue incident something to do with some kind of nose wheel steering failure causeing it to go full one way?


User currently offlineTristarSteve From Sweden, joined Nov 2005, 4024 posts, RR: 33
Reply 2, posted (7 years 6 months 4 days 15 hours ago) and read 6422 times:

Well wrong twice.
It doesn't turn 90deg, and it goes straight forward, not back.

The only gear I know that turns 90deg is the HS Trident MLG. This MLG had 4 wheels on a single axle, and rotated 90 deg on retraction to fit into the wing.


User currently offlineMeister808 From United States of America, joined Jan 2000, 973 posts, RR: 1
Reply 3, posted (7 years 6 months 4 days 15 hours ago) and read 6411 times:

Thanks - fixed the forward/back thing, brain fart on my part

Good to know I wasn't crazy.

-Meister



Twin Cessna 812 Victor, Minneapolis Center, we observe your operation in the immediate vicinity of extreme precipitation
User currently offlineViscount724 From Switzerland, joined Oct 2006, 25653 posts, RR: 22
Reply 4, posted (7 years 6 months 4 days 10 hours ago) and read 6364 times:

Quoting TristarSteve (Reply 2):
The only gear I know that turns 90deg is the HS Trident MLG. This MLG had 4 wheels on a single axle, and rotated 90 deg on retraction to fit into the wing.

That wasn't the Trident's only unusual landing gear feature. It also had the strange off-center nosegear that retracted sideways. As I recall that was to facilitate the location of the Trident's then state-of-the-art autoland equipment.


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User currently offlineRwy04LGA From United States of America, joined Jul 2005, 3176 posts, RR: 8
Reply 5, posted (7 years 6 months 4 days 9 hours ago) and read 6350 times:

The USAF XB-70 MLG also rotated 90 degrees before retracting rearward.


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Just accept that some days, you're the pigeon, and other days the statue
User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 6, posted (7 years 6 months 4 days 5 hours ago) and read 6309 times:

The centering cams will locate the NLG wheel in a Straight line along the Longitutional axis when the strut extends.
regds
MEL



Think of the brighter side!
User currently offlineTristarSteve From Sweden, joined Nov 2005, 4024 posts, RR: 33
Reply 7, posted (7 years 6 months 4 days 4 hours ago) and read 6296 times:

Quoting Viscount724 (Reply 4):
It also had the strange off-center nosegear that retracted sideways. As I recall that was to facilitate the location of the Trident's then state-of-the-art autoland equipment.

There was a myth around that the NLG retracted sideways so that the nose wheels did not hit the centre line landing lights when doing Cat 3 autoland.


User currently offlinePGNCS From United States of America, joined Apr 2007, 2834 posts, RR: 45
Reply 8, posted (7 years 6 months 2 days 11 hours ago) and read 6159 times:

It centers. In my A-320 AOM under the topic of Brake and Steering Control Unit (BSCU) it says "An internal cam mechanism returns the nose wheel to the centered position after take-off."

Hope this helps!


User currently offlineMir From United States of America, joined Jan 2004, 21684 posts, RR: 55
Reply 9, posted (7 years 6 months 2 days 6 hours ago) and read 6112 times:

Don't the main gear of the Tu-144 do some kind of funky retraction?

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 10, posted (7 years 6 months 2 days 5 hours ago) and read 6111 times:

Quoting Mir (Reply 9):
Don't the main gear of the Tu-144 do some kind of funky retraction?



Watch the Bounce.

regds
MEL



Think of the brighter side!
User currently offlineTristarSteve From Sweden, joined Nov 2005, 4024 posts, RR: 33
Reply 11, posted (7 years 6 months 2 days 3 hours ago) and read 6093 times:

Quoting Viscount724 (Reply 4):
That wasn't the Trident's only unusual landing gear feature

Also the Trident mainwheels were single wheels with two tyres on each wheel. I remember the trouble we had getting them off. They seemed to be an interference fit over the brakes, and more than once we had to remove the whole wheel/brake assy because the wheel would not come off!

Also strange was the emergency lowering of the gear. This used a compressed air bottle which blew high pressure air into the normal retraction jacks. You then had to use a turner adaptor to let the pressure out on the ground.

There was a lot of engineering on the Trident.


User currently offlineMemphis From United States of America, joined Mar 2006, 143 posts, RR: 0
Reply 12, posted (7 years 5 months 1 week 5 days 2 hours ago) and read 5711 times:

hey, isn't that the airwolf soundtrack???


nocturnal
User currently offlineMir From United States of America, joined Jan 2004, 21684 posts, RR: 55
Reply 13, posted (7 years 5 months 1 week 4 days 20 hours ago) and read 5643 times:

Quoting Viscount724 (Reply 4):
It also had the strange off-center nosegear that retracted sideways. As I recall that was to facilitate the location of the Trident's then state-of-the-art autoland equipment.

I heard it was because the autoland system was too good, and was putting the nose gear down right on the runway lights, which created a lot of vibration, so they chose of offset it.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17068 posts, RR: 66
Reply 14, posted (7 years 5 months 1 week 4 days 18 hours ago) and read 5617 times:

Quoting Memphis (Reply 12):
hey, isn't that the airwolf soundtrack???

Hehe. Certainly is.

Man that was loud inside!



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineBAW2198 From United States of America, joined Dec 2003, 637 posts, RR: 4
Reply 15, posted (7 years 5 months 1 week 4 days 13 hours ago) and read 5551 times:

Quoting Meister808 (Thread starter):
does the A320 family nosewheel turn 90° on retraction into the nose wheel well,

some aircraft that do are

The Beechcraft Sierra the nose wheel turns 90 and then retracts backward and the Piper Malibu (the older ones without the gear doors) which retracts in the same manner as the Sierra.



"And remember, Keep your stick on the ice"--->Red Green
User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 16, posted (7 years 5 months 1 week 4 days 6 hours ago) and read 5497 times:

Quoting BAW2198 (Reply 15):
some aircraft that do are

I don't think the A320 Nose Wheel turns 90deg on before retraction.The centering cam ensures its Straight.
regds
MEL



Think of the brighter side!
User currently offlineDH106 From United Kingdom, joined Jun 2005, 626 posts, RR: 1
Reply 17, posted (7 years 5 months 1 week 4 days 2 hours ago) and read 5486 times:

Quoting HAWK21M (Reply 16):
I don't think the A320 Nose Wheel turns 90deg on before retraction.The centering cam ensures its Straight.

Exactly - what would be the point?
Twin wheels are pretty much as wide as long so no real space saving.
Usually when they turn on retraction it's so a single wheel can lie flat and save space.



...I watched c-beams glitter in the dark near the Tanhauser Gate....
User currently offlineBAW2198 From United States of America, joined Dec 2003, 637 posts, RR: 4
Reply 18, posted (7 years 5 months 1 week 3 days 23 hours ago) and read 5448 times:

Quoting HAWK21M (Reply 16):
I don't think the A320 Nose Wheel turns 90deg on before retraction.The centering cam ensures its Straight.
regds

HAWK, I wasn't saying that the 320 did. Everybody above already answered that, I was just giving examples of planes that did use that retraction method.



"And remember, Keep your stick on the ice"--->Red Green
User currently offlineMoo From Falkland Islands, joined May 2007, 4021 posts, RR: 4
Reply 19, posted (7 years 5 months 1 week 3 days 22 hours ago) and read 5413 times:

Quoting Meister808 (Thread starter):
Ok folks, I guarantee this has been discussed before, but I can't find it - does the A320 family nosewheel turn 90° on retraction into the nose wheel well, or does it go straight forward? I can't seem to find anything that would suggest that it turns, but the topic came up in discussion and there's more than a few people I know that insist such a design was the reason for the well-publicized Jetblue incident at LAX last year.



Quoting B78710 (Reply 1):
wasn't the jet blue incident something to do with some kind of nose wheel steering failure causeing it to go full one way?

There was a very good reason for the Jet Blue incident last year, and infact the actions of the nose gear on that occasion was by design.

When the A320 series leaves the ground, a mechanical cam system centres the gear (as Hawk21M said). If this mechanism fails, the gear system does not infact know where the wheel is pointing with any certainty.

In order to provide for a safe landing in this case, the gear is rotated until it locks at the 90 degree point - its safer to land in this way and destroy the front gear and strut than it is to land with the gear facing an unknown direction with the potential for an uncontrolled forward motion off the central axis at speed.

Thats the reason for the 90 degree rotation.


User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 20, posted (7 years 5 months 1 week 2 days 21 hours ago) and read 5317 times:

Quoting BAW2198 (Reply 18):
I was just giving examples of planes that did use that retraction method.

My Apoligies.Guess I read the sentence Differently.

regds
MEL



Think of the brighter side!
User currently offline320tech From Turks and Caicos Islands, joined May 2004, 491 posts, RR: 5
Reply 21, posted (7 years 5 months 1 week 2 days 15 hours ago) and read 5288 times:

Quoting Moo (Reply 19):
There was a very good reason for the Jet Blue incident last year, and infact the actions of the nose gear on that occasion was by design.

When the A320 series leaves the ground, a mechanical cam system centres the gear (as Hawk21M said). If this mechanism fails, the gear system does not infact know where the wheel is pointing with any certainty.

In order to provide for a safe landing in this case, the gear is rotated until it locks at the 90 degree point - its safer to land in this way and destroy the front gear and strut than it is to land with the gear facing an unknown direction with the potential for an uncontrolled forward motion off the central axis at speed.

Thats the reason for the 90 degree rotation.

As far as I can tell, this isn't true. This incident had nothing to do with a failure in the centring cam, and there's hardly anything in there to fail, anyway.

It was actually a failure in the nosewheel steering system. An oring failed, causing hydraulic pressure to turn the wheels over to the mechanical stop, which is at the (approx, I forget) 86 degree position. This has happened several times.

You can read the article on Jet Blue flight 292. http://en.wikipedia.org/wiki/JetBlue_Airways_Flight_292



The primary function of the design engineer is to make things difficult for the manufacturer and impossible for the AME.
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17068 posts, RR: 66
Reply 22, posted (7 years 5 months 1 week 2 days 11 hours ago) and read 5260 times:

Quoting 320tech (Reply 21):

As far as I can tell, this isn't true. This incident had nothing to do with a failure in the centring cam, and there's hardly anything in there to fail, anyway.

It was actually a failure in the nosewheel steering system. An oring failed, causing hydraulic pressure to turn the wheels over to the mechanical stop, which is at the (approx, I forget) 86 degree position. This has happened several times.

If we ignore for a second the cause, didn't the gear go to the mechanical stop at about 90 degrees? That would seem to be the objective right?



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offline320tech From Turks and Caicos Islands, joined May 2004, 491 posts, RR: 5
Reply 23, posted (7 years 5 months 1 week 2 days 8 hours ago) and read 5236 times:

Quoting Starlionblue (Reply 22):
If we ignore for a second the cause, didn't the gear go to the mechanical stop at about 90 degrees? That would seem to be the objective right?

Well, my point is that having the gear rotate isn't a design feature, it's just the way it happens in that particular failure. I think the A320 is a well-designed airplane, but let's not give Airbus more credit than they deserve.  Smile



The primary function of the design engineer is to make things difficult for the manufacturer and impossible for the AME.
User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 24, posted (7 years 5 months 1 week 2 days 3 hours ago) and read 5205 times:

Quoting 320tech (Reply 21):
It was actually a failure in the nosewheel steering system. An oring failed, causing hydraulic pressure to turn the wheels over to the mechanical stop, which is at the (approx, I forget) 86 degree position. This has happened several times

What was the ADs Instructions like.
regds
MEL



Think of the brighter side!
25 Post contains links Troubleshooter : FAA AD 99-23-09 This is the only one I could find in a minute...
26 Starlionblue : From what I have heard it is in fact a design feature. I may be wrong of course.
27 320tech : I may be wrong, too. I'll see what I can find next time I'm at work.
28 HAWK21M : requires modification of the electro-distributor for the nose wheel steering servo-control Thanks. regds MEL
29 David L : I seem to recall from previous discussions that it was considered safer to land with the nose gear stuck 90o off-centre, producing no tendency to vee
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