744 body gear

[The Rage]

I was wondering if anyone would know anything on how the body gear on the 744, work as in to aline itself with the runway/track being made good on a cross wind landing. :O

[jtr]

BGS plays no part in x-wind landings. It only works when the tiller commands more than 20 deg nose wheel angle, and the speed is either blw 15kts on decel, or 20kts on accel. You can usually hear it when it kicks in <ggrrroooaaannnn shudder shudder shudder>

[Flight Detent]

Hi, 'The Rage',
On a B747 Classic, where this body gear steering system was developed, the system is much more manual (thank goodness!).

The same input from the NLG steering tiller is used, but the Capt/FE can disable the system by a simple switch selection when required.

Just prior to starting the takeoff roll, the FE disables the Body Gear Steering when the acft is lined up, ready. If the BGS is not properly aligned, it will do so then, and remain there until the switch is again selected 'On' at the slower end of the landing roll, unless the Capt takes a high speed runway exit taxiway, at which time the FE turns it on when the acft is slowed to taxi speed.

Operating in icing conditions, when taxiways/runways are very slippery, the acft can start a slide when a turn is initiated by the Capt, so the BGS is usually left turned OFF during these times.

The acft can be despatched with the BGS inoperative, but larger radius taxi turns are required.

Another reason why the Classics are better!
(It's just a real pity they are getting old and unreliable these days)

Hope this helps,

Cheers :ok:

[ballpoint]

Rage,

This phenomenon must have something to do with the yaw axis of the airframe being located just in between the body- and wing gears.
If the downwind winggear touches down a split second before the upwind winggear does, the asymmetric forces then pull the aircraft's nose away from the wind.
A pilot would know more. I'm an engineer, I don't fly...
Certainly body gear steering is not a question. This system is locked out during this flight phase, as mentioned before.

Regards, Ballpoint.