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I'm particularly thinking about larger aircraft with more than two sets of main landing gear.

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It's pretty obvious you would not want them to rotate while landing and take-off, but while taxiing around or being tugged, the drag caused by fixed axis wheels would be significant on tighter corners, and would leave rubber on the tarmac.

As such one would presumably want the wheels to track the turn.

That effect would be even worse for something like the Antonov 225... which I have no idea how they turn on the ground...

enter image description here

If they do somehow pivot, is there some sort of locking mechanism that is employed prior to take-off and landing.

Note this has nothing to do with crabbing for landing, but for ground maneuvers.

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For the 747 it does exist. It's called body gear steering. The two center bogies/trucks rotate when the nose landing gear exceeds 20° and the speed "decreases through 15 knots."

Both conditions would not exist during takeoff, and thus the system is locked. The 777 also employs body gear steering, as do many large aircraft. Such as the C-5 Galaxy. As for the An-225, someone says the aft 3 axles, but I couldn't corroborate it, but it is likely.

Body gear steering operates when the nose wheel steering angle exceeds 20 degrees. This reduces tire scrubbing and lets the airplane turn in a minimum radius. Body gear steering is activated when ground speed decreases through 15 knots. As speed increases through 20 knots, the body gear is centered and body gear steering is deactivated (747-400 FCOM).

The system reduces the asymmetric thrust needed for tight turns, and reduces tire scrubbing.

Here's the 777's via YouTube:

enter image description here

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  • $\begingroup$ Why only the center bogies? $\endgroup$ – TomMcW Jan 28 '18 at 20:58
  • $\begingroup$ @TomMcW - easier than all 4 and does the job. $\endgroup$ – ymb1 Jan 28 '18 at 22:09

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