HI, I don't know if this depends on the 737 or FSX itself or what, but in my home airport (Rome Ciampino - LIRA), 99% of the times it happens that on the approach, at about 1000-1200 ft agl, there is a point where the airplane experiences a small vibration and then the vertical speed suddenly goes from about -700 fpm to zero or even positive. Thus the airplane goes above the glideslope and it's not easy to recover the descent path. Even if the approach is flown by the autopilot this happens, V/S going to zero and the A/P must struggle in order to catch the glideslope back. It always happens at the same point, independently of the weather/wind conditions and without any external weather engine. The only thing I see in that point is that in that area the ground elevation smoothly increases from about 100 ft to 400 ft. Could that be a kind of ground effect due to the terrain being closer? In that case I don't think it's realistic, because the airplane is still at about 1000 ft and should not feel that altitude change.

I recall experiencing the same also during approaches on runway 25C at Frankfurt EDDF, although there the terrain is quite flat.

Any idea?

Thanks.

It sounds to me like there's a thermal on your approach. I've had this happen sometimes and it always makes for a go around or a really rough landing. Try going into weather settings and checking the box "Disable turbulence and thermal effects on your aircraft" and see if that helps.

Ok, thank you, I tried disabling and it seems that the problem is gone, but having the airplane not subject to turbulence is not what I want. I can't uderstand why I get that thermal effect every time and always in that point, is it something related to the ground mesh, landclass or what?

I experienced this effect at KSFO. It reminded me of a microburst, although I know these are not simulated in FSX. I would suddenly start floating, and would have to decrease throttle and pitch down, after which I would suddenly lose altitude and speed. I didn't quite mind, because it made landings more interesting. I now fly in Europe instead of the Americas.

I don't doubt that with this effect flights are more interesting. What bugs me is that in that approach I have always that effect at the same point, if it were a turbulence effect it would randomly happen, not EACH approach and at THE SAME point! Anyway I tried with another aircraft and it doesn't happen, so it must be the NGX that is influenced by something in that point. The question is: what is that causes this behaviour in the NGX?

Well that is the problem with what that box does, its effects are extremely unrealistic.

 

I suggest you would turn it off - you would still feel effects of turbulence by weather, and so....

I'm sure if you do a quick google search on removing thermals from FSX, you'll find something that will still let you have the turbulence effects.

 

Look for some info on thermaldescriptions.xml on the avsim forums...not sure if it will remove that one specific thermal...but you may be able to decrease it's effect.