Altimeters and Encoders

Bob Turner

Well-known member
Apr 4, 2018
Some years ago one of my students proudly stated he cruises at the altitude shown on the face of his Garmin transponder. A local pilot told me he was flying GPS altitude, and he felt that his altitude was more accurate than others.

Today during a flight review my student explained that he flies 200' high on his (properly set) altimeter so ATC gets the proper readout.

Instructors - stress this (along with not blocking runways and not blowing dust into others' hangars):

The only accurate source of altitude information in the cockpit is the altimeter. If you use any other source, you are reducing vertical separation and compromising safety. The altimeter may not match your actual linear altitude, but it does represent pretty much the same info that others in the same airspace are using. Altimeter settings put all aircraft on the same reference, accurate or not.