Transponders

A number of times I have switched on my transponder
and called for a clearance but ATC have not been able
to see me. I can see my transponder being interogated,
I have good battery power, everything seems to be working
but ATC still can't see me. This has happened to a
number of pilots I know.

So next time you set and forget... don't assume your
transponder is actually working.

If you don't call for a clearance you have no idea
whether you are transmitting or not.



At 17:00 23 January 2004, Bob Kuykendall wrote:
Earlier, Ben Flewett wrote:

...Once you agree to put transponders
in gliders you are obliged to use them
and they are a pain in the ass...

If that's on the basis of your personal experience,
I'd be inclined to
check if maybe you mounted the antenna the wrong way
up.

Where I fly, there are airliners. We have a letter
of agreement that
allows us one squawk code. No talking to Center; it's
just set and
forget. And, yes, there are officially rules about
always using the
transponder if it is available. Uh huh. Right.

Bob K.

Ben Flewett wrote:

A number of times I have switched on my transponder
and called for a clearance but ATC have not been able
to see me. I can see my transponder being interogated,
I have good battery power, everything seems to be working
but ATC still can't see me. This has happened to a
number of pilots I know.

Checking ocasionally is a good idea. In the US, you don't have to ask
for a clearance to determine this, but just contact the local tower or
approach guys and ask if they can see you. Actually getting the system
checked as required every 24 months is also a good idea.
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Eric Greenwell
Washington State
USA

Ben Flewett wrote:
A number of times I have switched on my transponder
and called for a clearance but ATC have not been able
to see me. I can see my transponder being interogated,
I have good battery power, everything seems to be working
but ATC still can't see me. This has happened to a
number of pilots I know.

If you don't call for a clearance you have no idea
whether you are transmitting or not.

Man, if I had a nickel for every time ATC said they didn't have
me but the airliner 10 miles out had me plain as
day, I'd have some nickels!

Too low, in line with another transponder, receiver too
far away, etc. If I let an ATC guy convince me to swap out
a $1000+ part, I'd get his avionics repair certificate number
first... ;(

Ben Flewett wrote:

A number of times I have switched on my transponder
and called for a clearance but ATC have not been able
to see me. I can see my transponder being interogated,
I have good battery power, everything seems to be working
but ATC still can't see me. This has happened to a
number of pilots I know.

Their have been similar cases to this in our club. It turns out that ATC
at Cape Town International had set their radar to filter out anything
moving slower than 40kt (ground speed). This I believe to filter out
stationery aircraft on the ground taxiing etc.

Gliders in wave simply disappeared off the radar screens, which did not
help anybody ...


Ian

Ian Forbes wrote:
Ben Flewett wrote:


A number of times I have switched on my transponder
and called for a clearance but ATC have not been able
to see me. I can see my transponder being interogated,
I have good battery power, everything seems to be working
but ATC still can't see me. This has happened to a
number of pilots I know.


Their have been similar cases to this in our club. It turns out that ATC
at Cape Town International had set their radar to filter out anything
moving slower than 40kt (ground speed). This I believe to filter out
stationery aircraft on the ground taxiing etc.

Gliders in wave simply disappeared off the radar screens, which did not
help anybody ...

Did the gliders have Mode C?

Is the radar for Cape Town just for the airport, or is it intended to
cover a much larger area?

In our area airport radar and the higher altitude radars are separate,
so even if the airport radar folks blanked slow moving traffic, Center
radar would see it.

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Eric Greenwell
Washington State
USA