Determining Stall Airspeed

Posted by drone1000 on March 7, 2015 at 10:31am

I'm trying to come up with a safe procedure to accurately determine stall airspeed for a plane with an airspeed sensor and ardupilot logging.  Any feedback on this technique?

1. Achieve stable level flight in full manual

2. Reduce throttle

3. Increase angle of attack to maintain altitude

4. Goto Step 2. until no longer able to maintain altitude

5. Stall has occurred, increase throttle and reduce angle of attack

6. Review flight logs to determine airspeed when control authority was lost

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Replies

  • Bruce Robb April 2, 2015 at 1:27pm

    A key requirement, I believe, is to place the pitot head away from the fuselage or wing such that it is in free air. I am using a hollow carbon tube as a boom extended from the nose to assess my stall speeds. Otherwise, I am following the method you describe above. I am then repeating the procedure in FBWA to establish if there is any difference.

    good luck

  • Eli Cohen March 7, 2015 at 11:32am

    you also might want to see how well the air speed sensor works at angles of attack near stall.... the static port should be fine but the pitot port might see larger pressure changes. depending on your plane, you can also take a pretty good wag at calculating stall speed based on wing loading and your wing's max Cl. 

    how accurately do you want to know it?

    this is also a handy reference for understanding stall performance: http://www.aviation.org.uk/docs/flighttest.navair.navy.milunrestric...

    • iskess > Eli Cohen March 7, 2015 at 12:06pm
      It shouldn't matter if there is some airspeed error because it will be consistent. You just need to know what speed to enter into the parameters, right?
  • iskess March 7, 2015 at 11:10am
    That plan should work good. Just avoid pulling back too fast, you shouldn't gain any altitude. You don't want an accelerated stall. You should do several in a flight to make sure you got a good sample. Be sure to calibrate your ASS first.
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