View Full Version : Roll Out Guidance.

5th Oct 2005, 17:06
Could someone please educate me on Roll Out Guidance, both from a pilots and tech viewpoint? What aircraft are equipped, standard & optional? At what speed does it disconnect? Presumably you need a Cat III Localiser to use it anyway.

5th Oct 2005, 17:51
>What aircraft are equipped, standard & optional?

Most modern airliners.

>At what speed does it disconnect?

It does not. You have to disconnect it manually in order to turn off the runway.

>Presumably you need a Cat III Localiser to use it anyway.

Not necessarily. Check your AOM and Ops Specs.

5th Oct 2005, 23:38
.. and, as a stick and rudder sim exercise, it doesn't take a pilot of average ability too long to get to the stage where a 0/0 hand flown raw data approach, landing and rollout to a stop on the centreline is a bit of a doddle .. not much practical use in the real world but it sure does put some polish on the IF skills and makes for a much more relaxed final endorsement checkout.

For this sort of exercise, roll out guidance is the localiser only ..

Old Smokey
6th Oct 2005, 05:34
At what speed does it disconnect?
It does not. You have to disconnect it manually in order to turn off the runway.
Yep, I noticed that None, every time that I try to steer off the runway after an Auto-Land. Undoubtedly I'll notice it again after my next Auto-Land. "What's wrong with the bloody steering now ?"

It just seems to be one of those thing that, like Groundhog Day, I'm doomed to repeat again, and again, and again.........


Old Smokey

7th Oct 2005, 11:48
Any other takers on this? Iím baffled. I may be a little out of touch but Iíve never heard of any automatics being connected to Nose Wheel Steering. My understanding of (landing) Roll Out Guidance was that the Nav Receiver used the Localiser signal to input Auto-Pilot rudder commands by which to maintain the centre line. When the airspeed decayed to around 80 knots the system disconnected.

7th Oct 2005, 12:03
At a guess, during the auto land would the yaw-damp still be on thus hampering nose wheel steering. I've landed with yawdamp on (once) and initially had no nose wheel steering. Thus below 80knots the steering would still be a prob.

7th Oct 2005, 13:32
757 & 767 have roll out guidance servos x 3 fitted to rudder. (In single autopilot flight, turn coordination is provided by yaw damper, not a separate rudder channel. Steering commands go to the roll channel).
The LOC active mode provides aileron commands to acquire and track the centerline of the localizer beam during all phases of single or multi-channel ILS approach. The A/P yaw channel provides rudder commands during multi-channel approaches to maintain runway alignment during rollout.

Yaw axis control functions provide directional control of the airplane during an autopilot dual or triple channel engaged controlled touchdown and rollout. During an ILS approach with two or three autopilots engaged, an FCC directional control module aligns the airplane on the centerline prior to touchdown and maintains the airplane on runway centerline after touchdown. During high speed rollout, the rudder is used for steering. Through an interconnect with the rudder pedals, nose wheel steering is used during low speed rollout.
Dis-engaged at A/P disconnect.

8th Oct 2005, 09:01

The 'Bus certainly steers you all the way to a full stop and remains connected until you physically disconnect the autopilot (or force steering more than 20 degrees or so from the centreline - I thnk!?!)

8th Oct 2005, 12:53
Thanks people. You live and learn, although the Ďlogicí here doesnít seem to follow through. If you take Auto-Brake, sort of related, that kicks-out with a touch on the brakes. Now youíve told me that nose-wheel steering is controlled, below the rudder control speed, Iíd have expected this to automatically disconnect with any Tiller or Rudder Pedal movement. Mind you, and aircraft apart, Iíve found that lots of things I Ďexpectí donít actually happen in reality.:hmm:

8th Oct 2005, 18:53
...and more of them [don't] happen differently in different airplanes! :eek: