Airspeed calibrations

[Ironflight]

Well Jeremy, you might get lucky - do the flight test acurately (hint - use your autopilot if you have one - they fly much more precisely than most of us), and see where you are. If not, I'd say you need Van's static port position....

Paul

[scsmith]

In your whole list of points, everything sounds OK, except your assumption of what you expect true airspeed to be based on your indicated airspeed.

As others above have noted, they are very different. True airspeed is true airspeed - its how fast you are going through the air.

Calibrated airspeed is the equivalent SEA LEVEL air speed that gives the same dynamic pressure (velocity combined with density) as you have at your altitude and true air speed, assuming everything in the instrumentation was correct. It takes a lot more speed to compensate for the lower density, so the sea level equivalent airspeed is lots lower than your TAS at altitude.

Indicated airspeed is what your gage says, with its errors from static pressure measurement error. If there were no errors, it would read the same as the calibrated airspeed.

[Radomir]

Just remember that all this works on a simple principle -- "Junk in -- Junk out" so if your indicated airspeed is wrong.. everything else (ie TAS readout) will be wrong too..

If you're using your EFIS as the encoder, then the ATC transponder readout won't help you either (again, junk in - junk out).

4-way run is your best bet to confirm how far off you are (sounds like you already did this). And I'll still say look at your static port.. as bad of a news as that is...

[voriii]

JJ
You mentioned available spreadsheets for calculating true airspeed from the GPS runs-could you give me a website for the ones you use-I can't seem to find the one I originally used for my RV10 runs.
Thanks
VO

[bruceg]

Hi VO,

I can send you a spreadsheet using the National Test Pilot School method for Excel 2008 for Mac computers if that would help.