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Is it just my imagination, or is it a fact that many large airliners actually touch down "crabbed" on difficult crosswind landings?

Here's what I mean in this video, or as shown in this picture:

enter image description here

Is the main landing gear specifically designed to allow this? Is it recommended or discouraged by the manufacturer?

Farhan
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Philippe Leybaert
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  • Related question about landing techniques & crab-vs-no-crab – voretaq7 Jan 23 '14 at 23:17
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    I enjoy watching crosswind landings way more than a reasonable human being should. – Cameron MacFarland Jan 28 '14 at 05:46
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    As I remember from initial ground school for the 747-100 and -200 in 1990, the recommendation was to simply touch down in a crab. In actual practice we typically used a combination of slipping and a crab at touchdown, how much of each depended on the pilot. In all but the heaviest xwinds you could take out the crab. I forget the max amount of wing down you could go, but I seem to remember that 5 degrees of wing down was fine, and that would get a lot of slip. – Terry Feb 12 '15 at 06:06
  • @Terry: It must take some skill to time the straightening up correctly. – copper.hat Feb 12 '15 at 07:12
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    @copper.hat It's a matter of timing, and it comes with a little practice. It's better to err on the side of not getting it straightened out before touchdown as all that means is you're touching down in a crab. If you get it straightened out too soon, the xwind will drift you sideways with respect to the runway. If that happens, put the crab back in and, possibly, more bank. It's not all that hard to time it well in a 747 or any aircraft that you're getting altitude calls from the radar altimeter or another crew member.. – Terry Feb 12 '15 at 07:49
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    @CameronMacFarland agreed, they are my "kitty videos" as well; well those and Russian Car Crash vids. :D – CGCampbell Feb 12 '15 at 13:40

1 Answers1

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The landing gear is indeed designed to cope with crabbed crosswind landings.

The recommendation is to avoid crab on landing however in severe crosswind conditions it is sometimes impossible to decrab completely without introducing excessive bank. Therefore some residual crab has to be allowed.

Airbus recommends less then 5 degrees of residual crab on landing, but aircraft are designed to cope with more.

An exceptional design is found in the B-52, where the main landing gear can rotated to be aligned with the direction of travel to deal with extreme crab angles.

DeltaLima
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  • Nice. The 747 in the picture above confirms that it can be a lot more than 5 degrees :-) – Philippe Leybaert Jan 23 '14 at 22:34
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    That's an All Nippon 747, as a Japanese Airline, they're into their drifting. – Jon Story Dec 19 '14 at 10:48
  • I was going to mention the B-52's rotating gear; good catch there. I wonder if any other designs have incorporated it. I know the 747's mains will rotate counter to the nosewheel to assist in taxiing on the ground, but if you were applying rudder to straighten out of a crabbed approach at touchdown, that system if active would point the wheels into the wind instead of down the runway. – KeithS Jun 24 '15 at 19:05
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    @PhilippeLeybaert this is not obvious. The aircraft may be going to the left of the runway, the angle of view may emphasize some angle and reduce other, and lots of more perception biais may exist. – Manu H Mar 14 '16 at 11:03
  • All Airbus aircraft have high clearance below the engines, so they can afford recommending lot of slip. Especially B737 has low clearance, so crabbing is recommended for it. – Jan Hudec Jul 04 '16 at 17:54