SAAFNAV
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Landing Gear Aligning With Crosswinds

Thu Jun 13, 2013 4:57 pm

Hi all,

I'm currently in a debate at work. The popular opinion is that the heavy birds like B747, A380 etc has the ability for the landing gear bogeys to turn sideways in preparation for a crosswind landing.

From what I know, the only aircraft that can do it is the B-52 with the x4 Main wheel bogeys, and the B747's wing main gear bogeys can turn while taxiing above a certain speed by arming them. Also, the B777's rear axle can steer as well, but that wouldn't help with crosswind landings.

Lieut's opinions don't count, so I'd appreciate an 'official' answer   

Thanks in advance!
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timz
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RE: Landing Gear Aligning With Crosswinds

Thu Jun 13, 2013 5:29 pm

Quoting saafnav (Thread starter):
The popular opinion

Suspect the popular opinion here is: no such thing.

Offhand guess: no tricycle-gear airliner has had a crosswind gear. They did try it on DC-3s in the 1940s-1950s; dunno if any airliners retained it.
 
vikkyvik
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RE: Landing Gear Aligning With Crosswinds

Thu Jun 13, 2013 6:05 pm

Quoting saafnav (Thread starter):
From what I know, the only aircraft that can do it is the B-52 with the x4 Main wheel bogeys, and the B747's wing main gear bogeys can turn while taxiing above a certain speed by arming them. Also, the B777's rear axle can steer as well, but that wouldn't help with crosswind landings.

B-52 gear can indeed be turned for crosswind takeoffs, and I assume landings, though I don't know.

B747 body gear can turn during taxi for improved turning radius and reduced tire scrubbing. The wing gear stays fixed. I believe A380 body gear can also turn, or maybe it's just the rear axle. B777 rear axle can also turn. C-5 aft main gear bogeys can turn as well, I think. AN-225 (and maybe -124?) has turning bogeys toward the rear of the main gear as well.

In general, with the exception of the B-52, these all only occur during taxi; far as I know, they're generally locked out during takeoff and landing.

Steering The Main Landing Gear (by Tupolev160 Sep 25 2012 in Tech Ops)
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SAAFNAV
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RE: Landing Gear Aligning With Crosswinds

Thu Jun 13, 2013 7:36 pm

Thanks for the replies.

That's what I thought, but I just wanted to make 100% sure before I take my stand.
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Starlionblue
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RE: Landing Gear Aligning With Crosswinds

Thu Jun 13, 2013 7:48 pm

AFAIK they do castor a bit, but after they touch the ground.
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Klaus
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RE: Landing Gear Aligning With Crosswinds

Thu Jun 13, 2013 9:12 pm

Quoting vikkyvik (Reply 2):
I believe A380 body gear can also turn, or maybe it's just the rear axle.

Indeed only the rear axle.
 
Okie
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RE: Landing Gear Aligning With Crosswinds

Thu Jun 13, 2013 11:20 pm

Quoting vikkyvik (Reply 2):
B-52 gear can indeed be turned for crosswind takeoffs, and I assume landings, though I don't know.

Yes for landings that was the main reason.
There was no ability to use standard crosswind landing techniques when your wing tips were inches off the ground.

Basically, the B52's fly the plane at the cross wind heading and offset the landing gear to the runway heading.

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Pihero
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RE: Landing Gear Aligning With Crosswinds

Thu Jun 13, 2013 11:27 pm

Quoting saafnav (Thread starter):
From what I know, the only aircraft that can do it is the B-52 with the x4 Main wheel bogeys,

That's correct, although it was tried on the B-47 first.
An interesting piece of aviation history is that this feature was otiginally on the C-5 prototypes and on the C-5A.
It disappeared on the C-5B and was subsequently removed from all C-5As.
Reasons were maintenace issues, complexity and improved landing techniques.
That swivelling capability was 20° and the system used inertial reference to orient the wheels in the direction of the aircraft heading.
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tb727
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RE: Landing Gear Aligning With Crosswinds

Fri Jun 14, 2013 12:47 am

Quoting Pihero (Reply 7):
It disappeared on the C-5B and was subsequently removed from all C-5As.
Reasons were maintenace issues, complexity and improved landing techniques.

Wow, there is already enough monkey motion going on with that gear, I couldn't imagine all that going on without breaking!
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KPWMSpotter
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RE: Landing Gear Aligning With Crosswinds

Fri Jun 14, 2013 1:11 pm

There were a number of light tail-wheel aircraft in the late '40s and early '50s which featured "crosswind gear". Most of these arrangements were after-market modifications to the main landing gear, allowing the axles to pivot freely 10 to 15 degrees. The most popular crosswind gear was on the Cessna 190/195, but I've seen similar arrangements installed on Cubs, Luscombes, and similar.

I have a book which shows some of the rather elaborate contraptions installed on Piper Cubs, I'll try to scan in some photos this evening.

As for heavy transport aircraft, the B747, A380, etc, cannot adjust their gear to compensate for crosswind landings. The 747 center bogies and the trailing axle of the 777 are steerable (I do not believe any of the main gear on the A380 are steerable), but only on the ground. The B-52, though, is rigged to land in a crab; the low wing tips of the aircraft prevent transitioning to a wing-low approach in a crosswind so the gear are adjustable to compensate.
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Klaus
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RE: Landing Gear Aligning With Crosswinds

Fri Jun 14, 2013 11:39 pm

Quoting tb727 (Reply 8):
Wow, there is already enough monkey motion going on with that gear, I couldn't imagine all that going on without breaking!

They're rotating for extension anyway, so I'd guess the actuation system was already present and only the reference target angle for the extended state needed to be modified.

C-5 Galaxy Landing Gear Extend

Quoting KPWMSpotter (Reply 9):
(I do not believe any of the main gear on the A380 are steerable)
Quoting Klaus (Reply 5):
Quoting vikkyvik (Reply 2):
I believe A380 body gear can also turn, or maybe it's just the rear axle.

Indeed only the rear axle.
 
KPWMSpotter
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RE: Landing Gear Aligning With Crosswinds

Sun Jun 16, 2013 6:06 pm

I found the crosswind gear excerpt that I referenced above. The below image is from "Piper Cubs" by Peter Bowers (the book is a treasure trove of odd modifications that have been made to the Cub).

http://imageshack.us/a/img27/3628/h77i.jpg
Uploaded with ImageShack.us
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