There are lots of excellent reasons for not requiring
gliders to carry transponders but this study seems
flimsy. In NZ we often have groups of gliders flying
together whilst using transponders - no problem.

The main reasons for not requiring gliders to carry
transponders a

- if airspace is managed well they are not required
in most areas. The real problem is that the groups
that draw the lines on the maps give the commercial
airlines more airspace than is required. For example,
Auckland (NZ) airport has more airspace around it than
Heathrow.

- as a glider pilot I don’t want to spend my day listening
to commercial pilots talking to ATC all day. I prefer
to have the radio tuned to a gliding frequency or off.

- most (but not all) controllers don’t understand how
gliders operate. The glider pilot is often required
to provide training to controllers whilst trying to
fly their glider. I don’t like having to do this…
“no, I am a glider which means I have no engine and
thus I cannot maintain 3000ft”.

- most glider pilots (including me) are not commercial
pilots and are not practiced at talking to ATC. Controllers
are used to speaking to commercial pilots and often
become frustrated with amateur glider pilots. The
also become frustrated with the unpredictable flight
path of gliders.

Once you agree to put transponders in gliders you are
obliged to use them and they are a pain in the ass.
If you only give commercial operators the airspace
they need there should be plenty left over for gliders.



At 18:36 22 January 2004, Marc Ramsey wrote:
Robert Ehrlich wrote:
An experiment in the french Alps made with a group
of tow planes
mimicking glider flight, i.e. circling together from
time to time has
shown that transponders, except in mode S, may not
be very useful in
gliders. As soon as 2 or more gliders are close together,
e.g. circling
in the same thermal of working together the same ridge,
they are hit
simultaneaously by the radar beam and generate simultaneaously
their
responses, which results in both interfering and nothing
useful
received at ATC. I had the chance of having one of
the engineers
involved in the experiment as a passenger last September
and he confirmed
this. In mode S, as each transponder is specifically
adressable,
this mess will probably not occur, a new experiment
using them is
planned.

This study is sometimes cited as an excuse to put off
installation of
transponders until inexpensive mode S transponders
are available. My
take on it is that it addressed a fairly narrow concern,
the possible
inability of ATC to properly discern a group of thermalling
mode C
equipped gliders. It did not examine whether airborne
collision
avoidance systems would continue to provide warnings
when confronted by
such situations.

The times when I've been surprised by the close approach
of larger
aircraft have been while cruising between thermals,
when I'm generally
alone or at a fair distance from other gliders. While
thermalling, I
have a view of pretty much the entire sky, and I have
a much better
chance of seeing approaching traffic in plenty of time
to avoid it.

Marc