ILS Bug

[RED]

I read something similar with NDB stations but could not find it:

The ILS stations are offline depending on wind which makes no sense to me.

 

Airfield Senaki Khohlki

Approach on RWY 09

 

If the wind is calm (3 kn) no matter what wind direction: ILS is offline.

If the wind is stronger - 10 kn - but comes from the west: ILS is offline again.

If the wind is stronger again and comes from the east: voilà, ILS is online.

 

Attached track shows the first setting with wind from the east.

 

Sidenote:

ED has interest in getting more virtual civil aviation pilots into DCS. But there are some major bugs for navigation in DCS. First you would have to understand how aviation navigation works and after that how it is working in DCS - e.g.:

ME and Briefing shows wrong wind direction.

Cockpit altimeter shows wrong height depending on temperature.

And now radio navigation stations depending on wind.

ILS-Bug.trk

[Frederf]

It is normal that runways which have radio navigation facilities with shared frequency for both ends of a runway will only power the facilities for the active runway. e.g. if 09 and 27 ILS are both 111.30 then only the active set will be working.

 

Given runway is 095 degrees true the cutoff between 09 and 27 active at 2m/s wind is 173-174 degrees direction. Relative angle is 101-102 degrees (mostly crosswind but small tailwind component). Finding tailwind component is cosine 101 and 102 which is -0.191 and -.208 respectively. One suspects a developer cutoff value of -0.2.

 

Oddly this is the changeover angle regardless of wind speed (1m/s 2m/s 3m/s 15m/s) which means changeover is not based on tailwind component but simply the cosine of the relative wind. It is angle-dependent and not component magnitude-dependent.

 

The ILS is shutting off at ~3m/s tailwind component magnitude. This is different behavior from assigned runway selection.

 

So we are left with the condition that the assigned runway is changing at a different time than ILS for inactive runway is put offline. There is a possible logic to this: change active runway to best direction but allow ILS to operate for wrong direction until conditions to get worse at which point shut it down. Remember ILS can be used for "circle to land" operations.

 

But we check Vaziani which has double-ended ILS of the same frequency. If we check different wind conditions we see that active runway changes but ILS does not until wind conditions change more. Under certain middle wind conditions the active runway is 32 but ILS is still active 14 (you will get ILS signal but it is back course 32) and ILS 32 inactive. In any case Morse ident for both ILS should not be identical to allow you to tell them apart (DCS they are the same).

 

Probably what should happen is some radio nav facilities should be programmed as dependent on some airbase variables and not try to have independent switching behavior. In most cases unless if facility conflicts with another (NDB or ILS frequency-sharing with another approach direction) then those facilities should remain operating regardless of active runway.

[RED]

Given runway is 095 degrees true the cutoff between 09 and 27 active at 2m/s wind is 173-174 degrees direction. Relative angle is 101-102 degrees (mostly crosswind but small tailwind component). Finding tailwind component is cosine 101 and 102 which is -0.191 and -.208 respectively. One suspects a developer cutoff value of -0.2.

 

Oddly this is the changeover angle regardless of wind speed (1m/s 2m/s 3m/s 15m/s) which means changeover is not based on tailwind component but simply the cosine of the relative wind. It is angle-dependent and not component magnitude-dependent.

 

The ILS is shutting off at ~3m/s tailwind component magnitude. This is different behavior from assigned runway selection.

Thanks for your insight Frederf! :thumbup:

 

I have made some different observation. Even with no tailwind component (my first scenario) the ILS is inactive when the wind is too calm. I will do more test on Vaziani this time - maybe if the wind is calm there are some strange behaviors.