Posted for Bob Pastusek <rpastusek@htii.com>:
Shannon,

You answered the question as far as I am concerned with the terms, "...
calculates a value..." The Sierra system doesn't have the needed inputs, in
it's current configuration, to accurately measure/calculate AOA. The
"computed AOA" they display has at least as many inaccuracies as the
airspeed indicator we are trying to improve upon with an AOA system. For my
two cents, keep your AOA system if it's based on airflow relative to the
fuselage/wing, or pressure measurements related to same. There probably are
some other ways to calculate AOA, but I don't know of any that provide the
weight/load/flight condition relationship to the airflow around your
airplane that one of these systems does. We're installing the SFS systems in
our IV-P's but intend to use Jim Frantz's AOA system as well.

Have to admit that I'm biased on this subject, having flown AF fighters for
a number of years that flew by, and depended on AOA for both optimum combat
performance and safe take off/landing operation.

Bob Pastusek