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Guest bkesl

Airspeed drops in turbolent weather

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Guest bkesl

Hi,I am looking for an answer to phenomena of airspeed decrease while flying via FS turbulent weather. Using PMDG 744 queen and Active sky 6.5 Whenever the weather becomes active, Clouds or other generated turbulence (VAS is Active sky)the airspeed drops slowly or in small steps until a point (if you let it continue dropping) when the stick shaker becomes active. The only recovery in this case would be to decent and pick up airspeed again. Increasing throttles setting to CON or GA or CLB will not help (most of the time).If more info is required please tell me.This one is really disturbing since in long haul flights I usually leave the sim running for hours (while attending real world duties...) and if the A/C bumps into such weather it will just crash.Any ideas?ThanksBenny K.

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I have seen unrealistic airspeeds due to weather simulation, but I'm only got guesses at it's cause. My foremost guess is that there is a large deviation from standard atmospheric conditions (especially temperature) that diminish the fidelity of the simulation.Turbulence does cause an airspeed to vary, but the momentum of the aircraft (mv^2) is such that the variations are brief and do not cause the aircraft to lose speed as you describe in cruise. Maybe the active sky forum can offer insight (they're located just below PMDG in AVSIM) on how to improve the behavior of the weather simulation, especially a problem where ground stations are extremely far apart.


Dan Downs KCRP

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I've have that problem but only when I have a tail wind building up. Usually the aircraft can't compensate when the tail wind builds from say 30 kts to 80kts in under 30 seconds. But I can usually build speed back up without decending but I do set eth throttles to CON. I too have AS6 but usually when I run into turbulence, the airspeed indicator shifts up and down but never more than a few knots.Ryan Gamurothttp://www.precisionmanuals.com/images/forum/supporter.jpg


Ryan Gamurot
 

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I use the wind smoothing features of FSUIPC (registered version) to control how rapidly winds can change velocity or direction. I consider it a must.


Dan Downs KCRP

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Guest bkesl

Thanks guys for the info.I went to the Active sky forum and it turns out that this is quite coimmon with ICING turned on in AS. I did not have the chance to verify that yet but I will.Benny K.

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Ryan the TAT <+10C is a good rule but can be restrictive whenin the cruise. If the SAT is colder than -40C then the anti ice can be turned off (generally only ice crystals) unless you are in severe convective precipitation. The wing anti ice should be used more as a deicer than anti ice. As a general rule turn it on and then off after around 3 min or when you can see the ice has gone. In the cruise wing icing is noticeable by decaying airspeed and/or a higher than normal cruise thrust setting. Also on the 747 the TAT probe tends to ice up at the same time and is a clue to check for wing ice.As a guide eng anti ice increases fuel burn by 100 kg/hr and both wing and eng anti ice by 300 kg/hr.CheersSteve


Cheers

Steve Hall

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