Wind direction anomaly

Hi,

mentioned this before but no solution, so again:

 

Ready for TO standing on runway 8 (see picture)

True airspeed indicator shows 6kts head wind (picture).

To the contrary the wind indication shows 7kts tail wind??? (picture)

Mysteriously ATC clears me to take off from runway 8 and announces tail!!! wind of 7kts???? (picture)

 

This anomaly is now happening all the time in last 3 months (all airports, all aircraft). Did not change any settings or weather download engine!!!

 

It NEVER happened to me before! the air speed indicator was always matching the wind indicator and ATC always

correctly offered take off from the runway with the

headwind!

 

Any help appreciated.

Thanks

Peter

That TAS gauge shows the speed of the aircraft, not the windspeed. So it is recording you as moving at 6 knots in the direction you are facing. If your brakes aren't on, that isn't impossible with a tailwind.

 

If there is any discrepancy it is the fact it is recording you moving at six knots when you think you are stationary but TAS is of no concern whatsoever whilst on the ground - you should use IAS:

https://en.wikipedia.org/wiki/True_airspeed.

 

I can't comment on ATC clearance to use that runway without knowing what airport you are at and which runways are closed to traffic. But the ATC messages you mention are correct for the conditions.

 

John

Just because a gauge tells you some info does not assure that it is telling you the correct info.

 

You seem to have two gauges confirming windspeed and direction...

 

Taking off with a 7 knot tailwind is acceptable and common in the sim (and the real world) where calm wind runway assignment is usually the runway closest to pointing North.

 

peace,

the Bean

My guess is that the True Airspeed gauge is actually displaying -6, but the gauge programmer never thought about a plane moving backwards in the air mass and didn't program for it.

Hi Beroun,

 

Try to set the wind speed higher, like 20kts or more, then change the time by 1 min. so the flight reloads and see if ATC now uses RWY26.

 

With low wind speeds other factors could take precendence to determine runway use.

Your RWY8 may be the primary end of the runway. RWY8 could have ILS approach code, while RWY26 hasn't.

 

Regards,

DDP.

Thanks Gents,

many thanks for your input. The takeoff runway offer from ATC was actually my fault since I had FSUIPC programmed to limit ground wind to 5kts. But even eliminating this limitation in FSUIPC ATC offers runways with tail wind even when now blowing from the back at 30kts or so. But I now contribute it to FSrealWX Pro I am using. This started about 3 months ago, in the past using FSrealWX Pro worked perfect with ATC offering correct head wind runway. For info not using FSrealWX Pro and just programing the User Defined Weather wind direction in default FS weather engine works OK. The ATC offers correct runway with headwinds, So the anomaly is apparently in FSrealWX Pro.

Apparently FSRealFX has recently changed. Solutions discussed at https://www.flightsim.com/vbfs/showthread.php?316628-Wind-direction-disregarded-by-ATC and elsewhere.

 

John

I've been seeing the same thing with FSRealWX Lite as well as Pro. It has been happening for a few months now. Changing the time by 1 minute will not fix it. My go to weather program is ASE but lately it shows me partly cloudy skies instead of overcast. So I have tried the other 2 programs. But they have the wrong runway syndrome. If I find a solution I'll be sure to post it.

Glad I am not alone. It surely looks like the FSRealWX is acting up. I am sure that the chaps will fix it. Have enjoyed it for many years and thanks for the freeware.