F-15C Nose whell SHIMMY BUG

[303_Vins]

After lock NWS, when faster than 60 kts nose wheel going shimmy vibrations.

Amplitude of vibration growing until tire damage, After that, nose gear breaks.

all situations: taxing, tKOFF, landing.

[BIGNEWY]

Hi

 

if you think there is a bug please include a short track replay showing the issue.

 

 

thanks

[303_Vins]

Hi

 

if you think there is a bug please include a short track replay showing the issue.

 

 

thanks

 

 

rgr. on my way

 

 

1- https://drive.google.com/file/d/1-v5DcK0o5chSe19IQHAaX_EopO5fUuGX/view?usp=sharing

2- https://drive.google.com/file/d/1Yl9VFetxsZA7FvRriIuniIq-foqPElF5/view?usp=sharing

 

 

50 kts is anough to start big amplitude Shimmy effect. This is a BUG. Normally Shimmy vibrations of nose wheel is well known by decades and is solved by every aircraft construction bureau long time ago...

I recommend to check all FC-3 aircraft and MiG-21 fot this issue.

Edited June 29, 2020 by 303_Vins

[=4c=Nikola]

Your tracks are locked.

 

Btw, tried to reproduce, it doesn't work. NWS (LALT + Q by default) does nothing in my F-15.

Edited June 29, 2020 by =4c=Nikola

[dundun92]

Your tracks are locked.

 

Btw, tried to reproduce, it doesn't work. NWS (LALT + Q by default) does nothing in my F-15.

Pretty sure its holding the S key for NWS in the F-15 unless I changed my default bindings (which I do occasionally).

[=4c=Nikola]

Pretty sure its holding the S key for NWS in the F-15 unless I changed my default bindings (which I do occasionally).

 

S key is NWS Gain.

 

Anyway, you need to hold LALT + Q to turn off NWS. In the past, it unlocked nose wheel so it would caster freely. Now it has some shimmy effect.

 

Not a big deal since no one really use the feature.

 

This is how it worked in 2014:

Edited June 29, 2020 by =4c=Nikola

[draconus]

Not a big deal since no one really use the feature.

There are some corners in taxi ways that have to use the higher gain of NWS.

[BlackLightning]

AFAIK, when on the ground, there is a certain range of speed in which the nose wheel should be kept free to steer like a wheel of a shopping cart because in that range the aerodynamic control surfaces are effective and so there could be a mismatch between the direction that the aircraft would follow according to the nose wheel and the one it would follow according to the rudder.

For an aircraft like the F15, this range could possibly be something like from 70 kts to takeoff, I think.

So when you takeoff at the beginning you supposedly keep the aircraft straight using the nose wheel up to say 70 kts and then you disengage NWS and use the rudders only; vice versa, when you land you initially use the rudders and then turn on NWS at 70 kts and use it until you stop.

In DCS, the NWS disengagement in the F15 works by keeping a button pressed: it's not an on/of toggle. If you disengage NWS either during takeoffs and landing you will blow a tyre; unless I'm doing something wrong, it must be a bug. I've attached a track file.

NWS.trk

[Lao Fei Mao]

After lock NWS, when faster than 60 kts nose wheel going shimmy vibrations.

Amplitude of vibration growing until tire damage, After that, nose gear breaks.

all situations: taxing, tKOFF, landing.

 

-----It's true. I found and got sick of it as a beginner. Then I never disengage the NWS during taking off or landing, all work well especially if your stick has a axis wheel brake like the VKB's.

[draconus]

I might have missed it the first time at post #7 but of course the NWS locking (LAlt+Q) in the F-15C is not used for normal operations. Described behavior is nevertheless a bug. Here is a track.

F-15C NWS lock.trk

Edited September 26, 2020 by draconus