calibrating airspeed?

[sunfish]

Are there settings that allow the airspeed to be calibrated once errors are known, or does SV do this for itself?

to put that another way how can we rely on indicated airspeed?

 

[airguy]

Typically you'll need to correct for position errors at the static port, by moving it or changing its height relative to the aircraft surface it's mounted on, or adding air-dams forward or aft of the static port, to get it to minimize error across the range of airspeeds the aircraft will see. To verify indicated versus actual airspeed a 3-direction GPS run will be needed to null out wind influence. You will likely need to repeat this process several times to get the corrections done right and zero out the error on the airframe.

 

[vlittle]

Typically you'll need to correct for position errors at the static port, by moving it or changing its height relative to the aircraft surface it's mounted on, or adding air-dams forward or aft of the static port, to get it to minimize error across the range of airspeeds the aircraft will see. To verify indicated versus actual airspeed a 3-direction GPS run will be needed to null out wind influence. You will likely need to repeat this process several times to get the corrections done right and zero out the error on the airframe.

There is a much easier way to calibrate airspeed.  Simply stabilize your indicated airspeed then engage the autopilot.  Do a complete rate 1, 360 degree or more turn using the autopilot 180 turn function. Also, note the time displayed on the screen.

Do this at several different airspeeds.

On the ground, examine the datalogs.  Choose the minimum and maximum ground speed in the log when you are flying the circle, they should be 180 degrees apart.  Average these two numbers.  This now your calibrated true airspeed.

Repeat this for each airspeed test that you flew.

Compare your computed vs indicated true airspeed to get the error.  If you want, you can uncorrect to get the indicated airspeed error.

If you want, you can also enter the data from three different headings 120 degrees apart into the spreadsheet to confirm the numbers.

Of course, this method works best in stable air. It's all there in the datalogs.

V

 

[sunfish]

yes, but is there any way of adjusting skyview to match indicated and true?

 

[dlloyd]

No way to adjust Skyview. See reply #1.

 

[airguy]

It's not a "Skyview" thing - it's an "aircraft" thing. Any aircraft, regardless of what instrumentation is installed, is subject to position error for both the pitot tube and static ports, and these errors need to be physically corrected.

 

[kellym]

yes, but is there any way of adjusting skyview to match indicated and true?

Indicated and true will only be the same when you have std conditions and zero altitude. I think you mean matching calibrated and indicated. I don't know of a way to do that, besides getting your static port located in a neutral pressure area.

 

[GalinHdz]

Or putting an air dam in front or behind the static hole depending on what your error is. Here is a link to a thread covering this issue in depth.

http://www.vansairforce.com/community/showthread.php?t=145686&highlight=static+error