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Landing Gear Aligning With Crosswinds  
User currently offlinesaafnav From South Africa, joined Mar 2010, 285 posts, RR: 1
Posted (1 year 5 months 2 weeks 3 days 4 hours ago) and read 4088 times:

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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11 replies: All unread, jump to last
 
User currently offlinetimz From United States of America, joined Sep 1999, 6896 posts, RR: 7
Reply 1, posted (1 year 5 months 2 weeks 3 days 3 hours ago) and read 4050 times:

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.


User currently offlinevikkyvik From United States of America, joined Jul 2003, 10258 posts, RR: 26
Reply 2, posted (1 year 5 months 2 weeks 3 days 3 hours ago) and read 4043 times:
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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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User currently offlinesaafnav From South Africa, joined Mar 2010, 285 posts, RR: 1
Reply 3, posted (1 year 5 months 2 weeks 3 days 1 hour ago) and read 3997 times:

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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User currently offlineStarlionblue From Greenland, joined Feb 2004, 17118 posts, RR: 66
Reply 4, posted (1 year 5 months 2 weeks 3 days 1 hour ago) and read 3986 times:

AFAIK they do castor a bit, but after they touch the ground.


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineKlaus From Germany, joined Jul 2001, 21495 posts, RR: 53
Reply 5, posted (1 year 5 months 2 weeks 3 days ago) and read 3927 times:

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.


User currently offlineokie From United States of America, joined Jul 2003, 3151 posts, RR: 3
Reply 6, posted (1 year 5 months 2 weeks 2 days 21 hours ago) and read 3808 times:

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.

Okie


User currently offlinePihero From France, joined Jan 2005, 4634 posts, RR: 77
Reply 7, posted (1 year 5 months 2 weeks 2 days 21 hours ago) and read 3802 times:
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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.



Contrail designer
User currently offlinetb727 From United States of America, joined Jun 2005, 1631 posts, RR: 9
Reply 8, posted (1 year 5 months 2 weeks 2 days 20 hours ago) and read 3765 times:

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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User currently offlineKPWMSpotter From United States of America, joined Dec 2006, 457 posts, RR: 2
Reply 9, posted (1 year 5 months 2 weeks 2 days 8 hours ago) and read 3591 times:

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.



I reject your reality and substitute my own...
User currently offlineKlaus From Germany, joined Jul 2001, 21495 posts, RR: 53
Reply 10, posted (1 year 5 months 2 weeks 1 day 21 hours ago) and read 3386 times:

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.


User currently offlineKPWMSpotter From United States of America, joined Dec 2006, 457 posts, RR: 2
Reply 11, posted (1 year 5 months 2 weeks 3 hours ago) and read 3110 times:

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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