Aircraft prone to uncommanded left roll

[effte]

Well, if a roll to the left can be confirmed, we know it is not right!

[ff4life4]

[Bestandskraft]

This is cross-posted at http://forums.eagle.ru/showthread.php?t=139846&page=2.

 

I can confirm with 100% certainty that the cause of the uncommanded rolls in 1.2.15 is the wind.

 

Very easily reproducible:

 

Create any mission with zero wind at all altitudes. Provided your HOTAS is properly calibrated, the aircraft is symmetrically loaded and you do not accidentally apply any rudder, the aircraft will fly straight.

 

Using the same mission, set wind e.g. to 180/50 (km/h), no turbulence. When flying headings 090° or 270°, the aircraft will roll away from the wind. When flying headings 180° or 360°, there will be no roll.

 

The effect is more pronounced the higher the wind speed you set, and the higher the crosswind component.

 

I have only tested this in MiG-21bis 1.2.15, not in any other aircraft or version of DCS.

 

Based on my understanding of aerodynamics, this behaviour is not entirely realistic. While it is a well-known technique to apply "aileron-into-the-wind" during take-offs to counter the phenomenon that the upwind wing will experience more lift, thereby causing the aircraft to roll away from the wind during lift-off, once entirely in the air, the aircraft is moving with the air mass surrounding it, and steady wind should have no effect on aircraft roll, while wind GUSTS will of course have a temporary effect.

 

See for example https://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/airplane_handbook/media/faa-h-8083-3a-3of7.pdf, pp. 5-5 to 5-8.

 

I'm not an aerospace engineer, so there might be an aerodynamic effect I'm not aware of that would cause roll effects due to steady winds after all. I have simply never heard anyone complain about having to trim the aircraft to counter steady enroute winds in a real-world context. If anyone can find something on this matter online I'd be very interested in seeing it.