Pattern Help

[Bill Glaze]

Bob:
Probably correct.  I've flown light planes wherein the airspeed 
indicator would read ridiculously low at high angles of attack.  The 
high angle that the pitot tube is presenting to the relative wind, 
(which distorts the apparent shape of the inlet) won't allow the full 
pressure to pressurize the tube.  Hence, false airspeed readings.
Bill Glaze

Bob Richards wrote:

> 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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