Peter Purdie wrote:
The large altimeter takes up a lot of space and provides the least
important info..........................we can all estimate our
altitude for landing, can't we? The rest of the time its just nice to
know info.
Except when you're flying in the among controlled airspace, where
neither GPS altitude (geometric) nor transponder altitude (QNE) do you
any good. Loggers usually can give you QNH altitude, provided you set
them correctly and your battery isn't flat.

Transponders give Flight Level (assuming they are working properly),
so will give the altitude ATC are intereted in. That's how they
know what FL you are at when not talking to them.

The pilot still needs to know msl altitude, because that's how the
airspace is designated at 18,000' and below in the USA. Also, elevations
(airports, mountains, obstructions, etc) use msl, and other gliders and
aircraft will report their altitudes in msl.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org