correct as-is The Viper is much too tippy when taxiing into a curve

[wernst]

It has been reported here several times how difficult it is to keep the Viper on the runway with nose wheel steering after touchdown.

Worse still is the tendency to tip over when rolling into a curve. Even at a moderate roll speed (e.g. 20 kts) you have to be prepared for the wingtips to scratch the ground. You have to take any turn carefully smooth like butter. It gives the impression that the Viper is as light as a feather, as if the jet has no weight on its wheels, like a plastic toy plane. The Viper is more tippy than any other aircraft in the sim. 

Does the real Viper show the same behavior?

Edited August 27, 2022 by wernst
correction

[Furiz]

Viper has that problem since it was designed and it is well known, the front wheel had to be moved backwards cause of the intake, it is not under the pilot like with other planes, you can google picture and see for yourself, that and small distance between 2 rear wheels make Viper really prone to tipping.

And yes you really need to be careful with landing specially in crosswind, it is a light fighter as you said like a toy plane, everyone has trouble landing it in crosswind. I think I never saw a "Show me your landing" thread in any plane forum section, only Viper has it. That tells a lot too

 

[MAXsenna]

3 hours ago, wernst said:

Even at a moderate roll speed (e.g. 20 kts) you have to be prepared for the wingtips to scratch the ground. You have to take any turn carefully smooth like butter. 

I haven't read this manual, but in another Viper sim, it says do not do turns over 10 knots. Keep at 7-8 and I can pretty much sling it around.

What are you using for rudders? 

Edited August 27, 2022 by MAXsenna

[Dragon1-1]

Yup, well known quirk of the Viper IRL. Taxi slow, turn very slow. One airframe had the bad luck to get tipped over twice, not sure what the first one was (pilot error, maybe?), but the second time is a well known incident with being blown over by a B-1's jetwash. This is something to keep in mind when taxiing the Viper.

[Versor]

Change your rudder curvatures to 30% or even 35%. Without this is realy hard.

[skywalker22]

25 minutes ago, MAXsenna said:

I haven't read this manual, but in another Viper sim, it says do not do turns over 10 knots. Keep at 7-8 and I can pretty much sling it around.

What are you using for rudders? 

 

From Chuck's manual:

[wernst]

30 minutes ago, MAXsenna said:

I haven't read this manual, but in another Viper sim, it says do not do turns over 10 knots. Keep at 7-8 and I can pretty much sling it around.

What are you using for rudders? 

 

20 kts was just a first guessing, I measured my typical taxi speed and it's not higher than 10 kts. Rudder: Saitek Pro Flight combat rudder pedals.

Of course, with much care I can manage it to get around the curve safely, but I wonder what happens IRL when a alert start is needed.   

Edited August 27, 2022 by wernst

[skywalker22]

Since we are on this low taxing speeds, the HUD does not show speeds bellow 59 CAS and 70 TAS. But it does show speed in Ground mode from zero up. Is this ok?

[Dragon1-1]

13 minutes ago, wernst said:

Of course, with much care I can manage it to get around the curve safely, but I wonder what happens IRL when a alert start is needed.   

Alert fighters are typically kept where they don't have to taxi very far. Tipping over and blocking taxiway is even less conductive to quick reaction scenarios than taxiing slowly.

Viper IRL has wide, short throw transducer pedals. Far more precise than a Saitek rudder, but the actuation force is very high. This allows the pilot to make very fine pedal inputs. You still can't go fast, though.

8 minutes ago, skywalker22 said:

Since we are on this low taxing speeds, the HUD does not show speeds bellow 59 CAS and 70 TAS. But it does show speed in Ground mode from zero up. Is this ok?

Yes. Airspeed comes from the pitot tubes, ground speed comes from INS and GPS. The former needs enough airflow over the tubes, the latter only needs an aligned INS. You can also see ground speed on the INS alignment page on the DED, this is a convenient way of viewing it during taxi.

[skywalker22]

5 minutes ago, Dragon1-1 said:

Yes. Airspeed comes from the pitot tubes, ground speed comes from INS and GPS. The former needs enough airflow over the tubes, the latter only needs an aligned INS. You can also see ground speed on the INS alignment page on the DED, this is a convenient way of viewing it during taxi.

That's what I thought, but needed to ask to make sure.

[MAXsenna]

22 minutes ago, skywalker22 said:

That's what I thought, but needed to ask to make sure.

Yup! Like @Dragon1-1 said.

10 was fine. 16 Not so much.

Edited August 27, 2022 by MAXsenna
Nulls

[MAXsenna]

48 minutes ago, wernst said:

20 kts was just a first guessing, I measured my typical taxi speed and it's not higher than 10 kts. Rudder: Saitek Pro Flight combat rudder pedals.

Of course, with much care I can manage it to get around the curve safely, but I wonder what happens IRL when a alert start is needed.   

 

I don't use curves, but I changed my TM T.Flights for some Slaws (with a damper) this summer. Made a huge difference and they are worth the price. The T.Flights were not all that bad, once I got some Nyogel in them, but they are a little narrow, and the toe brakes are rubbish.

Remember to line up correctly, and turn off NWS as soon as you "can", and don't turn it on immediately when you land. Get SLOW!

[skywalker22]

46 minutes ago, MAXsenna said:

Yup! Like @Dragon1-1 said.

10 was fine. 16 Not so much.

 

Or this knob to GND SPD position on have speed on the HUD:

[MAXsenna]

24 minutes ago, skywalker22 said:

Or this knob to GND SPD position on have speed on the HUD:

Aahhh! Excellent! Thanks. Didn't think of that!

[silverdevil]

1 hour ago, skywalker22 said:

Or this knob to GND SPD position on have speed on the HUD:

ah!! i saw this post and was going to ask. how the heck does anyone know how fast of ground? i have been just doing it by feel. i have been initiating NWS on landing after the rudder stops working. it gets squirrelly for sure. 

[Dragon1-1]

If you need to steer between rudder and NWS speeds, use differential brakes. Turn it on only when reaching taxi speed.

[wernst]

2 hours ago, skywalker22 said:

Or this knob to GND SPD position on have speed on the HUD:

Great, thanks skywalker, I didn't notice that there is an easy accessible and accurate display of the ground speed. I ran a ground roll test using this exact display to see how sensitive the tippy tendency is in relation to ground roll speed when turning into a 45 deg. curve. 

1. Viper with no payload and 50% fuel: turns into a 45 deg. curve is possible between 15 and max. 20 kts without tipping.

2. Viper with max payload and 100% fuel: turns into a 45 deg. curve is possible between 15 and max. 20 kts without tipping.

I didn't expect the result because I assumed that more weight on the wheels would give more stability against tipping. Conclusion: In the sim it's not. 

All in all, I see now that there is no big issue, tippy is less worse than I thought first. 

[Dragon1-1]

41 minutes ago, wernst said:

I didn't expect the result because I assumed that more weight on the wheels would give more stability against tipping. Conclusion: In the sim it's not. 

It doesn't work that way with aircraft. Tipping depends on where your center of gravity is, and since it's not a static condition but a dynamic one, absolute value of mass doesn't matter much. CoG in aircraft can't move too much in absolute terms because even small changes have a big effect on stability. Moment of inertia could change, which would have an effect on the tipping process, but I don't know if that's simulated and I wouldn't expect a big effect, either. With such a short and narrow wheelbase, you'd be hard pressed to avoid such behavior.

[enyak]

You can get a sense of how the F-16 taxies around a steep corner here at 05:55. It's a pretty deliberate speed but I kind of get the sense that angle might still have thrown our DCS Viper.

 

Edited August 28, 2022 by enyak

[Dragon1-1]

Sense of speed can be very different between exterior and interior view. Real aircraft typically taxi slower than most DCS pilots do, for fear of hot brakes and other trouble. Quite often, minimum taxi speed is where it's at. Take off time is planned so that you have plenty of time to taxi and don't have to hurry.

[silverdevil]

On 8/27/2022 at 7:44 AM, skywalker22 said:

Or this knob to GND SPD position on have speed on the HUD:

thanks for this again!! i have been clueless wondering why i could never see ground speed on the HUD. i opened, what i think is called a manual, and found where the switch was. movement on the ground was so much easier.

[TheSkyfox]

Its my understanding that in real life 15kts is the normal on most airbases.

[mvsgas]

direct PDF link AFMAN 11-2F-16V3

RELEASABILITY: There are no releasability restrictions on this publication.

page 15, para 3.3.1

Quote

Unless mission requirements dictate, pilots will limit taxi speed to 30 knots, 15 knots over a raised cable, and
10 knots in turns.

 

 

[Jel]

As long as it makes ppl realize DCS is not "NFS underground 3",  tippy is fine.

Edited August 29, 2022 by Jel

[silverdevil]

Taxi on snow and ice. Now we're talking.