On Wed, 30 Aug 2006 13:57:47 +0000, Mike Schumann wrote:

Why in the world would you leave a transponder off if you have the luxury of
having one????

Transponder installations in gliders are not as reliable as we would like
them to be. These are some of the reasons I know of for transponders not
being operational in VFR airspace that I have experienced by myself or by
other pilots I know personally:

- Battery failed unexpectedly and no backup installed.

- Battery failed unexpectedly and backup battery also failed unexpectedly.

- Transponder display faulty and spares unavailable (a common problem
with old Terra's).

- Loose connection between the altitude encoder and transponder resulted
in wild altitudes indications and ATC getting upset and requesting the
pilot to switch off the transponder. ATC also not happy with pilot
squawking mode A.

- Antenna located a little too close to pilot for comfort and pilot elects
to leave transponder switched off to protect the family jewels from
radiation when not in controlled airspace.

- Transponder operating but transmissions shielded by poorly
located antenna.

- Antenna damaged by earlier ground handling mishap and transponder
switched off.

- Transponder turned on but the pilot is unaware that it is non-functional
because it has not been ground checked for a long time and the glider has
not been in controlled airspace recently and hence the pilot has not had
confirmation from ATC that they can see him.

- Transponder is turned off because the pilot suspects it is not
working but has not had a chance to get it checked either on the ground,
or by talking to ATC.

- Transponder removed for repairs and sent to repair facility and it takes
many weeks to get it back.


And a couple of other reasons reported on RAS:

- Glider pilots requested to switch off transponders in certain
areas after false TCAS warnings triggered at nearby airports.

- Transponder set to squawk code that is filtered on ATC radar.

(Please note, I don't fly in the USA, none of the above occurred in the
USA so please don't quote me USA regulations.)

From my experience, it is feasible to fit transponders in a few privately
owned gliders for use during occasional flights in controlled airspace (or
other airspace with active communication with ATC).

However, it is not practical to equip an entire fleet of gliders with
transponders, instruct the pilots to squawk "blind" and expect this to
allow IFR traffic to be routed safely through the same airspace. This is a
recipe for disaster.


Ian