IAS to CAS

[skyview_user]

Hi Dynon, is there a way to correct IAS to CAS? The wind and other computations are wrong if not....
Thanks for an answer.

 

[GalinHdz]

There is no way to "correct" IAS for CAS in the SkyView becasue, in a well designed system, IAS and CAS should be within a few knots of each other. An error like this normally indicates a problem with the location of your pitot/static system. The problem will show up as errors in speed, winds, altitude and other calculations. This has been discussed in multiple threads with the last one happening just a few days ago.

Always shows a headwind

No matter what my direction I always show a headwind which translates to a slower than accurate groundspeed. When I change direction the indicator will change to about 45 degrees then flip to a headwind. What is going on? HDX1100 new install on RV14.

forum.flydynon.com

 

[skyview_user]

Sorry. That was not my question. My system has no errors. I only want to have correct values.

 

[GalinHdz]

Sorry. That was not my question. My system has no errors. I only want to have correct values.

There is no IAS to CAS correction capability in SkyView, or any other name brand EFIS that I know of, because IAS and CAS should be within a few knots of each other. I hate to say this but it sounds like your system has a dynamic airflow error which makes wind, altitude and other calculations wrong. Not that uncommon with EAB aircraft. I had this same situation in my airplane.

 

[skyview_user]

hi dynon,
could you pls answer my question, i.e. given IAS, known CAS, how to enter the correction into SV? Thanks

 

[RVDan]

If your pitot static system has no errors (not likely errors are 0) then, IAS=CAS. In a typical static system there will be < 3 kts error between the two, which in the scope of the wind calculations is small enough to be ignored. No EFIS that I am aware of allows the entry of CAS to correct IAS.

 

[Raymo]

Why not use TAS, which the system already provides. In zero wind flight, TAS will match ground speed.

 

[GalinHdz]

In zero wind flight, TAS will match ground speed.

Not if the pitot/static system is providing the EFIS with a wrong IAS value. In a modern EFIS, TAS is calculated based on IAS, among other variables, so a wrong IAS will give a wrong TAS. "Garbage in, garbage out."

 

[Dynon]

Hi Dynon, is there a way to correct IAS to CAS? The wind and other computations are wrong if not....
Thanks for an answer.

There isn't a way to do this.