Pattern Help

[Bob Richards]

Earl,
 
I'm not familiar with that device, but I will make two assumptions. 1) The altitude transducer works on barometric pressure. 2) The pitot tube works just like on a full scale plane.
 
I suspect the unexpected zero airspeed has to do with the airflow at the tip of the pitot tube not being parallel with the pitot tube due to the high rotational speed of the snap. In an extreme case, the airflow traveling perpendicular could actually cause a vacuum in the pitot tube.
 
If the altitude measurement works on barometric pressure, there must be a static air source. I suspect the vertical speed anomaly is caused by a change in the static air pressure due to the sudden change of airflow around the airframe, including the static air source.
 
Just guesses.
 
Bob R.
 

Earl Haury <ehaury at houston.rr.com> wrote:
While recently evaluating engine / prop combinations (very top secret), I noted something that looks useful regarding snaps. During both up and downline snaps the speed signal drops to zero for a period of time roughly equivalent to snap duration. It appears that possibly airflow separation from the wing includes the pitot tube. Upline snaps also show a marked decline in ascent rate during the snap. 
 
 
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