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Old May 17th 09, 05:56 PM posted to rec.aviation.homebuilt
Wayne Paul
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Posts: 905
Default Building an electronic Angle of Attack indicator


"Dan D" wrote in message ...

A very 'slippery' glider takes a while for the airspeed to settle down
after a pitch change. Flying to an exact AOA would be easier than
chasing airspeed.

An AOA indicator that shows minimum sink and maximum L/D as well as
stall would be quite useful.


The glider solution could be a simple as the piece of yarn along the side of the canopy...


It isn't that simple. The string will show the angle of flow relative to the fuselage, not the airfoil. The fuselage angle of max L/D and minimum sink change with the flap setting. (Thermal at 15 degrees, cruise between zero and -10 degrees.)

A true AOA would supply a single given Max L/D indication no mater what the flap setting. The software to do this isn't difficult if you know the airflow relative to the fuselage, the angle of incidence of the wing, and the wing's performance curves for various flap setting.

From my perspective a reliable low-drag encoding vane is the tall pole in the tent. The airfoil performance/angle of incidence can be derived from sailplane's handbook. The cockpit indicator can be the designer's/owner's choice.

Wayne
HP-14 N990
Flap range -10 to +90.
http://www.soaridaho.com/Schreder/HP-14/N990/N990.html