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rnordquest
31st Mar 2009, 02:09
I have input into the design of a new nose wheel steering system but have never used one myself. At what speed do you want NWS to be selectable for use? Would there be any difference between TO and landing and why?

I realize your training may allow you to prefer a less than best design because of familiarity so the more systems you've been exposed to the better. My personal guess is that you want to transition to rudder control as soon as it becomes effective so I'll need that speed too.

Obviously I'm looking for cut out speed on TO and cut in for landing. Digital control can do things like speed proportional steering but functionality like this is a problem for certification/verification test and cost. I think a simple honest system is preferred to a wiz bang one that may require 500 warning and fault messages.

Therefore, my plan is to ask the user what he wants as opposed to what the airframer thinks they want to supply.

Thanks for you help,

Roger

Flight Detent
31st Mar 2009, 02:36
Just install a system just like the NG and all will be fine!

A Comfy Chair
31st Mar 2009, 02:47
When you say selectable for use, I hope you don't mean you have to actively select it on and off.

It also depends what sort of aircraft it is for.

I've used them on the 744 and 767 and they work well, and so far I've never heard any adverse comments from the Airbus guys either.

I'd have a close look at those systems, because, to be honest... they work, and I can't see too many reasons to fiddle with them.

Intruder
31st Mar 2009, 02:52
If you've never used one, maybe you should get the feel for a few before you give your input...

I've flown airplanes where the NWS could not be used on the runway, those that used it all the time, those that had separate tiller and pedal-controlled NWS, and those with none at all. It depends too much on the airplane and the responsiveness of the NWS.

rnordquest
31st Mar 2009, 04:45
This is for a new RJ size plane. And yes you do have to select it to use it but all you do is place your hand on the control wheel to select. Grab it and it works, let go and it's off. The separate control wheel will be off on the side somewhere for both crew.

rnordquest
31st Mar 2009, 04:48
Flight Detent - I take this to mean that you prefer just to use your feet and not a hand operated one. Am I correct?

Bullethead
31st Mar 2009, 05:07
G'day rnordquest,

I dunno about the B737 but on the B767 & B747 there is both a tiller and also nosewheel steering through the rudder padals. The rudder pedal steering has limited authority, about 7deg either side of centre, while the tiller gives full control and overrides the rudder pedal steering.

Directional control during the takeoff run initially is through the rudder pedal steering until the rudder itself becomes effective, at around 40kts, then the nosewheel castors. It's all mechanical and it all works well.

In the event of a nosewheel steering failure the aircraft can still be steered by using differential braking and or asymmetric thrust.

Regards,
BH.

Intruder
31st Mar 2009, 15:28
I don't know that the NWS ever disconnects from the rudder pedals on the 747, as long as the nosewheel ground sensor switch is made. In fact, it is required for Cat III Rollout guidance.

The body gear steering deactivates automatically at 20 Kt on the 744 (there's a manual switch on the Classic).

rnordquest
1st Apr 2009, 01:06
Good stuff guys

The phases are tiller, rudder pedal NWS, rudder pedal NWS & aero, rudder pedal aero only. If you can think of more, let me know. At what speeds are you comfortable? i.e. do you want to drop the tiller asap or would you rather hold on to it as long as possible?

I think what they're planning is reduced authority at higher speeds and maybe even speed proportional. The tiller would be available for all.


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