N2310D wrote:

"Ron Lee" wrote in message
Never say never, as the old saw goes....
Having said that, I would never use my GPS altitude indication for
anything other than driving my car over the Rockies or Sierras.
On the other hand, the KLN-89B in the 172SP I used to fly had the
ability to dial in the local baro setting. I don't recall the delta between
the 89B and the legal altimeter being more than 20 feet with the baro date
set in. Biggest problem was the 89B altitude info was all but useless for
anything other than audible altitude deviation alert. That and having to dig
out the book and flip through the pages to remember how to input the baro
data. And, as I recall the altitude alerting was not legal for Part 91
either

You input the baro by hitting the ALT button. Not sure much page flipping
is required for that. But entering in the current pressure is to allow
an input pressure altitude to be compensated for, not the altitude calculated
from the GPS satellites. Finding the GPS altitude does require a certain
amount of buttonage. You must have had MODE S , my MODE C will only be within
100 feet of my "legal" altimeter.

--
Don Poitras