Re: Rudder control & front gear

From:         geohull@ditell.com (George Hull)
Organization: DirecTell L.C. - Park City, UT. - 1.801.647.0214
Date:         27 Apr 95 02:53:21 
References:   1
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In article <airliners.1995.451@ohare.Chicago.COM>, wdockery@pipeline.com
(Wayne Dockery) wrote:

> Is a commercial aircraft (e.g., B747), I understand the
> plane is controlled by the rudder for 'yaw'.  However,
> once on the ground does the pilot have to make some
> change to steer the craft with the nose gear vs. the
> rudder?  In other words, are the rudder pedals also
> used to steer the nose gear?

Typical airliners and large transport aircraft us a combination of systems
to steer on the ground.  The nose gear is equipped with what is called
nose wheel steering.  It is controlled at slow speeds using a tiller to
the captain's left (and sometimes that control is duplicated on the first
officer's side).  Large deflections of the nose wheel are made using the
tiller.  The nose wheel steering is also controlled within a more limited
angle by the rudder pedals.  So an airliner is normally taxied using the
tiller until it is lined up on the runway for takeoff.  The tiller is
abandoned once the aircraft is tracking normally on the centerline of the
runway.  Then the steering is done using the rudder pedals as the aircraft
gathers speed.  The control becomes aerodynamic at approximately 60 knots
and the same rudder pedals are then controlling the direction of the
aircraft using a combination of nose wheel steering and rudder
deflection.  It all works very seemlessly during the takeoff roll.
Whenever the rudder pedals are depressed the rudder is deflected . . but
at low speeds it has no aerodynamic effect.  Watch an airliner taxi away
from the terminal and you'll see the crew check the controls.  The captain
holds the tiller steady as he exercises the rudder while the first officer
runs the ailerons and elevators through their check (typically).

George