Originally Posted by IO540
With an altitude encoder you have no way of knowing if it is out of calibration, and if the aircraft in question does not have a transponder then the pilot may never realise it is out
Does it make sense to have an altitude encoder without a transponder? I often get asked to state my indicated altitude after being given a squawk code, presumably so ATC can confirm if my transponder is working correctly.
Originally Posted by IO540
GPS altitude seems to be a really easy way to deal with this, especially with EGNOS coming in soon, offering vertical accuracy of the order of a few feet or better.
I wonder why Garmin decided to implement EGNOS in the old GPSMAP 296, but not in the new Aera 500?