Terrible ground steering

[lnuss]

In the real world C172 there is no connection between the rudder control and the nose wheel. The nose wheel casters in response to other forces. At low speeds the brakes and then as speed increases, the rudder.

Hmmm... you've flown a different C-172 than I have, then. On all the Cessna singles I've flown (tri-gear, that is) the nosewheel is connected to the rudder pedals via springs, thus not a direct connect, but not free castoring, either. And the brakes DO enhance the steering, when used carefully. But I can understand how you might get that impression, especially if you came from a Piper with the directly connected nose wheel.

[jandjfrench]

Hi Inuss,

I'll give you the full story. When I first started to taxi I was used to steering with a joystick. When the C172 started to move I moved the rudder pedals with no effect and the instructor said that I had to use the brakes. I said "Isn't the nosewheel linked to the rudder?" He looked at me for a moment then got out, looked, and got back in and said "No." I didn't think too much more about it until some time after I got pedals. I was amazed at how accurately taxiing felt in FSX compared to the real thing. And when I thought about it, I went into spot view and moved the rudder pedals and saw that the nose wheel didn't move and was impressed.

Now, it seems that I recall seeing springs attached to the nose wheel and while not disputing what you say still reserve a bit of doubt that they are not there just to keep the nose wheel straight and are not coupled to the rudder control.

Jim F.

[Perry266]

Thank you for taking the time to respond to my problem. I have decreased the sensitivity to around 20% and am currently playing with the yaw settings. I am a low time pilot with some 173 and 170 time. The only real issues were p-factor when I honked down on the throttle. When taxing, I could jockey between toe brakes and rudder to get to my destination without tearing up the real estate. Thanks.

[lnuss]

...still reserve a bit of doubt that they are not there just to keep the nose wheel straight and are not coupled to the rudder control.

 

The "no effect" is actually just a slow response, Jim, and it won't turn as far as when you add brakes -- you can steer with just rudder pedals, but it's not the sharp effect you get on a Piper, and you can't make a sharp turn without using the brakes. But it does enable you, even with crosswinds, to taxi without brakes most of the time, and you normally can make takeoffs and landings without using the brakes for steering, unless the crosswind is awfully strong. On the Grummans (and other free castoring aircraft), if you need to steer at all you have to steer with the brakes (rudder pedals are useless for that) until you get enough airflow over the rudder to steer with it. Believe me, it's a different action. Of course with this linkage, pressing the rudder pedals when sitting still does not cause the nosewheel to turn at all -- you have to be moving, in contrast with the Pipers (if you can get enough strength on the Piper's pedals when it's standing still, they'll move).

 

When the Cessna nose wheel lifts off the ground, it extends a bit and this forces it to be straight, by design. This is neat, because even with a lot of rudder applied in a crosswind landing, the nosewheel is straight when it touches, therefore not causing a swerve, and the spring linkage allows it to not suddenly engage and cause a swerve. On the Pipers, if you have rudder applied as the nosewheel touches, you'll get a bit of swerve, though you soon learn to compensate.

 

Of course once the nosewheel is compressed (on the ground) again, it is again affected by the pedals through the spring linkage.

 

All that said, though, the brakes do make for a quicker response, and aid steering a lot. But an aircraft with a free castoring nosewheel (Grumman Tiger, Cheetah, et al) has a very different feel to it.

 

Hope this helps.

[Perry266]

Thank you Larry.

Perry266

[ScatterbrainKid]

Nosewheel damping- I don't know if this has been mentioned, but when I had an ultra-realistic jet combat flight sim a few years ago (i think it was the F-16), the nosewheel could only be turned to its maximum at low speeds during taxiing, but at higher speeds it could only be turned a few degrees to stop the pilot accidentally ripping it off by too coarse rudder movement, because the nosewheel automatically sensed the high speed and damped down its movement limits.

I think some real-life aircraft have the same restrictions, including airliners, but I don't know if FSX simulates it.

[jandjfrench]

Hi Inuss,

That does help immensely. And I appreciate the tactfulness of your response. I Googled it after I posted and couldn't find any information that described the Cessna steering anywhere near as well as you have. When I looked at the images I came across they were nothing like what I was imagining. The image of seeing springs is more likely related to some Polaroid pictures I took years ago. I was into RC and I drove around Half Moon Bay (CA) airport and took a lot of pictures. I'm suspecting the tail wheel of a Cub. It seems that times have changed regarding airport security.

Thanks again for the great description.

Jim F.

[lnuss]

Glad it helped, Jim. The Cub springs are, of course, external, as are those on most tailwheel aircraft with steering (some castor), but on the Cessnas the springs are internal.

 

Times have, indeed, changed when it comes to airport access, though there are still a few smaller airports that are accessible.

[pvarn]

The actual code API FS uses to model nose wheel steering is much more simplistic and does not get into the detail about how the gear, wheels, and suspension are constructed. It's all controller sensitivities, steering angles and how the suspension reacts to the loads and weights for animation purposes and retraction/damage speeds/loads.

 

There's no detail about linkage, springs vs cables, hydraulics, whether the wheels decouple on take off or any of that kind of stuff. The AIR file has additional stuff like maximum braking strength and the balance of braking between front and main gear. the dynamics modeler simply determines how much controller input will turn the gear how much. How the plane reacts to these controls is really the fine point and it's all in inertia and weights, nothing having to do with mechanical parts and how they are constructed.

The code can disable the gear if hydraulics fail and stuff like that, but in the the end, the gear turns or not. The gear is touching a ground surface or not. The controller has deflected so much percentage of maximum, so turn the gear this much.

 

Some models do not have nose wheel steering animation so the wheels will look like they are not swiveling even though turning forces are being applied and the model turns. How the gear looks in reaction to the controller is fully determined by the 3D modeler. In addition, in FS there is really no direct coupling between aircraft functionality and the 3D model. The dynamics modeler, the gauge designer, sound designer and the 3D visual modeler all have their own code sets and they can decide independently how things look and feel and whether something will be modeled at all.

 

The result of this is a lot of smoke and mirrors and hopefully a model that behaves as expected to real world specification. Who cares how you got there? On the other side of the coin, there is a lot of opportunity for all the designers of a model to slack off and not model certain things at all or only partially.

 

All that matters is learning how your particular model handles and refining your technique. There is no standard the modelers have to follow. Some shoot for the details and for some, if the plane loads into the sim without a crash they call it good.

Every controller is different too. There is no standard on how any controller feels or responds. Add to that each user can change the feel of the controller to their liking regardless of how that device might work on the real plane. This results in controllers and how they feel and operate being like a ruler made of paper flapping in the wind.

 

If there is a real world theory on nose wheel design that helps you visualize how to cooperate with the handling of a particular model, then it's all good and if the plane behaves like the real world specifications indicate it should, then chalk that up to thousands of hours of quality testing by the designers, not because they put a spring or a strut or a cable here or there. Those things don't exist in the sim. What they CAN do for certain kinds of specialized gear is disable steering under certain conditions. Most do not bother with that level of detail.

 

The 3D designer can create what looks like a cement brick and the dynamics modeler can make the brick fly like a kite. The 3D designer can leave all control surfaces and wheels off with no animated parts and the thing will still take off, land, turn and stop. The 3D modeler can create the most awesome looking aircraft ever and the dynamics code can make it sit there and do nothing.

 

-Pv-