F-18 NWS Hi

[Stubbies2003]

Posting this here as well since the link from the manual took me to the Belsimtek forum and I am seeing some issues being posted here.

 

Okay I've gone through the manual and haven't seen any talk of this problem I've noticed in the F-18. I have a Thrustmaster Warthog setup and I have the rudder set to the slider on the throttle.

 

During normal NWS steering the aircraft behaves normally. However if I enable NWS Hi and am either hard over left or right on the rudder the aircraft will start to steer in the correct direction, then slow down to a straight path then REVERSE the turn to the opposite direction of the input. This happens with wings unfolded on land during taxi and with wings folded on a carrier deck.

 

Through testing I have found that if I limit the rudder input to roughly 2/3rds or perhaps 3/4ths of what the slider can go to then NWS Hi works just fine.

[Harker]

That happens when you're too fast for NWS HI. Your front wheel skids on the floor. Go slower and it won't.

[bbrz]

Nevertheless the plane shouldn't start turning into the wrong direction. I've noticed this weird behaviour as well. This worst thing that happens IRL is that the plane continues in a straight line.

[Harker]

Do you mean that it goes in the wrong direction a lot? The worst I've seen is that it might wobble a bit towards there, but then it'll go straight if I'm fast.

I can definitely use the full rudder in NWS HI for very tight turns, but I have to be very slow.

[Laud]

What Harker said. Also don't step on it too fast but increase the throw slowly. For the tightest radius you'll need to use momentum instead of thrust as that would push you straigt ahead. This means you'll not be able to make endless circles with max. NWS throw.

 

 

Going in the opposite direction could be a result of wind after having come to a full stop (environmental + carrier speed).

[bbrz]

Going in the opposite direction could be a result of wind after having come to a full stop (environmental + carrier speed).

I'm exlusively using land based runways and even at 0 wind the F/A-18 turns into the wrong direction with full rudder deflection if you enter the turn at a too high speed.

 

If you e.g. taxi at 10kts and apply full right rudder with the steering in HI, she will start to turn to the left and even if you reduce the speed to below 5kts she will continue turning to the left.

 

If you apply full rudder at e.g. 5kts you can do extremely narrow turns, into the correct direction of course.

[Stubbies2003]

So I went ahead and re-tested this just to verify it wasn't a taxi speed issue. It isn't. On land or at sea only in NWS Hi I can duplicate this issue and I can duplicate it at VERY low speeds. Like 1-2 knots worth at best. Obviously due to that low speed the effect isn't as fast or as great but it does it consistently.

[Deano87]

So I went ahead and re-tested this just to verify it wasn't a taxi speed issue. It isn't. On land or at sea only in NWS Hi I can duplicate this issue and I can duplicate it at VERY low speeds. Like 1-2 knots worth at best. Obviously due to that low speed the effect isn't as fast or as great but it does it consistently.

 

Try applying the steering more gradually, if you snap to full steering it will cause the problems you’re seeing.

[RudeS]

The thing that happens when you apply full NWS Hi from the start, is that the wheel will deflect full and start dragging/slipping/sliding over the tarmac, instead of the wheel turning to provide steering as it should. At least that is what I think happened here.

 

Have you tried looking at your nose wheel with F2 while you reproduce the issue you're talking about?

[Guppy]

This comes down to 2 issues:

1) too fast.

2) engaging NWS Hi and cranking all the way to left/right before slight forward motion is applied.

 

Once you get used to how slow you have to be you will find yourself not having issues.

[majapahit]

do F2 and observe

[bbrz]

The point is, if you are too fast, too high steering angle, at no point does any plane IRL turn into the opposite direction of the steering input, regardless if it's skidding etc.

[majapahit]

The point is, if you are too fast, too high steering angle, at no point does any plane IRL turn into the opposite direction of the steering input, regardless if it's skidding etc.

This has already been discussed, and it does because of the offset of the nosewheel (presumably), the definite cause can only be verified by an actual pilot, and they're prob reluctant to address any of a subject this stupid

[Guppy]

This has already been discussed, and it does because of the offset of the nosewheel (presumably), the definite cause can only be verified by an actual pilot, and they're prob reluctant to address any of a subject this stupid

 

Whoa - no need to get offensive. OP had a legit question, be nice.

[bbrz]

This has already been discussed, and it does because of the offset of the nosewheel (presumably), the definite cause can only be verified by an actual pilot, and they're prob reluctant to address any of a subject this stupid

The only stupid thing here is your response.

You have apparently no idea how easily a nosewheel can start skidding IRL and I don't know what kind of magic 'offset' should be responsible for this physically impossible turning behavior.

 

I suggest you simple take a look at this video:

[Deano87]

The wheels are behind the steering axis. When you have nearly 90 degrees of steering angle to the left the wheels are actually in contact with the tarmac to the right of the nose. Once they start sliding and are no longer providing useful steering then they are producing a dragging force on the right hand side of the nose. It makes sense to me why this would drag the nose to the right instead of the commanded left.

 

 

See:

https://forums.eagle.ru/showpost.php?p=3626810&postcount=12

[majapahit]

The only stupid thing here is your response.

You have apparently no idea how easily a nosewheel can start skidding IRL and I don't know what kind of magic 'offset' should be responsible for this physically impossible turning behavior.

 

I suggest you simple take a look at this video:

You're linking to a massive passenger jet? Why?

[bbrz]

When you have nearly 90 degrees of steering angle...

But that's the crucial point. The angle is not 90deg, it's alway less.

 

Another important point is that the nosewheel usually carries only 15% of the airplanes weight.

If the nosewheel doesn't provide any steering input, the tiny amount of 'offset' would be way too low to cause this effect, if the nosewheel would actually be turned 90deg, which it isn't.

 

@majapahit, why not? Weight distribution is very similar and I haven't seen any other video which demonstrates this unintenional skidding this obvious.

[Wizard_03]

The wheels are behind the steering axis. When you have nearly 90 degrees of steering angle to the left the wheels are actually in contact with the tarmac to the right of the nose. Once they start sliding and are no longer providing useful steering then they are producing a dragging force on the right hand side of the nose. It makes sense to me why this would drag the nose to the right instead of the commanded left.

 

 

See:

https://forums.eagle.ru/showpost.php?p=3626810&postcount=12

 

Makes sense, your in a quasi drift at this point. Need to be very slow and smooth with Hi.

[Deano87]

But that's the crucial point. The angle is not 90deg, it's alway less.

 

Another important point is that the nosewheel usually carries only 15% of the airplanes weight.

If the nosewheel doesn't provide any steering input, the tiny amount of 'offset' would be way too low to cause this effect, if the nosewheel would actually be turned 90deg, which it isn't.

 

The wheel doesn’t need to reach exactly 90 degrees. Once the tyre is sliding at maximum steering angle (lets call it 85 degrees.) then It’s literally just sliding rubber across the tarmac, it doesn’t really matter which angle said rubber is being held at by the nosewheel and it doesn’t matter if the wheel rotates during this process, it won’t be contributing any meaningful steering input to the nose.

 

As I’ve said before though. If you taxi the jet properly then you won’t run into any problems. Get a small amount of forward speed before starting the turn. And when you start the turn input steering angle gradually so that the nose is already swing in the direction you want to go before you get to full steering angle. Don’t put full steering angle and try to set off from stationary, then you’ll probably slide.

[Stubbies2003]

The thing that happens when you apply full NWS Hi from the start, is that the wheel will deflect full and start dragging/slipping/sliding over the tarmac, instead of the wheel turning to provide steering as it should. At least that is what I think happened here.

 

I could see it slipping or dragging if the issue was too much speed and too much turn but as stated I can duplicate this at VERY low speeds. Deano87 is probably on to it as I had already known that putting in about 2/3rds or 3/4ths of rudder instead of full eliminates this problem completely.

 

 

Have you tried looking at your nose wheel with F2 while you reproduce the issue you're talking about?

 

 

Nope haven't done the F2 view for that.

[Stubbies2003]

This comes down to 2 issues:

1) too fast.

 

 

As I stated in my re-test post I can duplicate this when hardly moving at all.

 

 

Once you get used to how slow you have to be you will find yourself not having issues.

 

 

I already don't have issues with it since I already knew the counter for the issue. I was simply reporting the issue.

[Stubbies2003]

Wow this one got all sorts of salty on page 2. So for anyone wanting the TL : DR just don't go hard over in either direction in NWS Hi and you'll be fine.

[Wizard_03]

Even at slow speed, if you jam the pedals around the tires are gonna slide. It’s a big heavy jet with relatively small wheels, in a tricycle configuration. NWS has to use enough hydraulic pressure to turn the wheels under the jets weight. Think If you could turn a steering wheel in a car as fast as you can pedal turn. You probably could create a similar situation. This behavior seems reasonable IMHO.

[Stubbies2003]

OK I am only posting on this one again to link a video of some F/A-18 deck ops just to prove that the real bird can do these super tight turns. Precisely like the one I brought up so no if you are going slow enough it isn't going to behave like it currently does in DCS. DCS it doesn't matter what speed you taxi at the odd behavior of it centering then turning in the wrong direction is still there.

 

Fast forward to 13:40 if you only want to see the nose wheel turn 90 degrees to the right and turn just fine. Watch it all for the enjoyment of seeing the professionals at work.

 

No need to respond. This is mostly so the folks in charge of the F/A-18 can see this needs fixing in DCS.

 

Edited September 25, 2019 by Stubbies2003