On 3/4/2011 11:44 AM, John Smith wrote:
Darryl Ramm wrote:
The TT21 is a class 2 transponder and therefore *not* suited for
gliders. If you choose to go with Trig, then do yourself a favour and
buy the TT22.

The TT21 is very suitable for gliders. Its being installed in many
gliders in the USA and I expect elsewhere. The issue between class 1
and 2 transponders comes down to a fairly meaningless difference in
output power when you compare 15,000' vs. the maximum altitude we
typically fly at.

If you ever want to climb above 15,000 ft in an airspace where a
tansponder is mandatory (which I do regularly), then you are just plain
illegal with the TT21. This may be "fairly meaningless" for you, it's
not for me and should not be for any pilot.

The USA, where Darryl flies, does not have a requirement for a
transponder in the 15K to 18K airspace.

Can someone explain where the reason for the 15,000' limit for the lower
power transponders? It seems rather arbitrary to a USA pilot.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm
http://tinyurl.com/yb3xywl