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Old 20th Apr 2015, 01:09
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No Fly Zone
 
Join Date: Jun 2013
Location: Or-E-Gun, USA
Posts: 327
B747 Taxi & Turning Operations

Some details and guidance from those who know, please...

Given: Most low speed 747 (1-2-3-4-8?) directional control is provided by tiller orders to the nose gear. Limited nose wheel control is available via the rudder pedals, but I understand that this is limited to about 6-7 degrees and is really intended for brief periods of increasing rudder control while accelerating for TO.
I've just learned that the 747, at least in some editions, provides some degree of BLG steering control, assumed to be similar to the counter steering often seen on extremely long urban fire apparatus, to enable negotiating tight turns in confined spaces. My questions about the 747's BLG steering include:
1. Is this automatic, or under manual control of the taxiing pilot?
2. Do I have it right, in that this is actually a counter-steering function, either holding the wheels straight or turning them 'counter' to the intended direction of the turn?
3. How many degrees of deflection are available?
4. --- In actual practice, how does it really work? Do pilots like it, dislike it, or simply never think about it?
5. Is this feature common to all B747 editions or perhaps an (extra cost) option? Perhaps it is a feature that has changed its stripes over the years?
6. Whatever you know and can share is greatly appreciated. Thank you!


Ah yes... Of course, once more question! Can the 747's BLG offset be used during extreme cross-wind landings(*), or is it limited to ground taxi functions only?
(*) In past generations, a few VLA have had a MLG offset function available for cross-wind landings. The C-5 and B-52 instantly come to mind, but there may be others. As I recall, the feature was quickly disabled on the C-5 and then eliminated from the design of future generations. For the apparently everlasting B-52, now flown by the grand and great-grand children of its designers, I have no clue. (It sort of sounds like a crazy idea, but for an airframe with floppy wing spread of the B-52, perhaps it is necessary. Again, I have no clue. If you know, beyond the B747, do any other Very Large civil aircraft offer this feature?
Thanks, boys and girls. Any details, leads/links or insight are greatly appreciated.
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