Cockpit weather display question

OK, so there I was, training one of our scarce "newbie" controllers at ZTL
yesterday. There was a lot of convective weather and we were busy busy busy
trying to keep people from killing each other in the saddles and holes
between the storms. Anyway, as usual when I am training someone and its
crazy busy, something came up that I'd never seen before. Hopefully one of
you guys can fill me in.

We've got an aircraft at FL170, headed south inbound the Atlanta terminal
area, where the weather is really going bad. I forget the airplane type, it
seems it was a C210 but I can't remember. He's about 150 NM north of ATL.
The pilot calls my trainee and asks for permission to turn off his
transponder for five minutes so that he can "Go download the latest
weather". The trainee had to ask the pilot to say his request again, and
then looked askance at me for an answer. All I could say was "Well, that's
a new one for me, bud. Let him do it and we'll see what happens". His
transponder was only off for a minute or maybe two tops, not the five he
asked for. We were too busy to do what I'd normally do, which is ask the
pilot on the spot for a brief education on what he is up to.

I thought I understood the basics of some of the new in-cockpit weather
tools for GA aircraft. I figured he was getting the latest Nexrad picture
from some online resource. What I don't understand is why he needed to turn
his transponder off to do so. Any help appreciated.

Thanks,

Chip, ZTL

"Chip Jones" wrote in message
nk.net...
[...]
I thought I understood the basics of some of the new in-cockpit weather
tools for GA aircraft. I figured he was getting the latest Nexrad picture
from some online resource. What I don't understand is why he needed to
turn
his transponder off to do so. Any help appreciated.

First I ever heard of something like that, but I've never used these
inflight weather download services, so it's not like I'd know.

The most likely explanation I can think of is that the transponder might
operate on a frequency that interferes with the download, either making it
incredibly slow and/or unreliable, or even impossible to download weather
while the transponder is operating.

However, I would have thought that the people who have developed these
inflight weather download equipment would have considered that, and run into
it during product testing. It seems hard to believe that one could get TSO
approval for a device that only works if you turn off your transponder, but
I guess since any TSO would be more about not interfering with other
equipment than whether it's interfered with, it's certainly possible AFAIK.

Other thoughts assume an even more hacked-together system: not enough power
from the electrical system to power the transponder at the same time as the
weather download receiver; a shared antenna that has to be manually switched
from the transponder and the download receiver.

I sure hope someone else has an actual explanation, though I wouldn't bet on
it.

I can't imagine that this is something that applies to every inflight
weather download installation though.

Pete

Peter Duniho wrote:

I can't imagine that this is something that applies to every inflight
weather download installation though.


Let's hope not!

On Sun, 18 Jul 2004 21:32:18 GMT, "Chip Jones"
wrote:

SNIP


.. He's about 150 NM north of ATL.
The pilot calls my trainee and asks for permission to turn off his
transponder for five minutes so that he can "Go download the latest
weather". The trainee had to ask the pilot to say his request again, and
then looked askance at me for an answer. All I could say was "Well, that's
a new one for me, bud. Let him do it and we'll see what happens".
SNIP
I thought I understood the basics of some of the new in-cockpit weather
tools for GA aircraft. I figured he was getting the latest Nexrad picture
from some online resource. What I don't understand is why he needed to turn
his transponder off to do so. Any help appreciated.

Thanks,

Chip, ZTL



Chip,

I think he must have been using Anywhere Map WX softare. One of the
way's it gets the Nexrad is via a Satphone. I think I remember a tech
note on their support page mentioning interference on the WX download
with certian King transponders. I bet he had one of those
transponders.

"Chip Jones" wrote:
The pilot calls my trainee and asks for permission to turn
off his transponder for five minutes so that he can "Go
download the latest weather".

Weird. Perhaps his transponder causes interference with his wx
receiver. If so, he *really* needs to get that fixed.
--
Dan
C172RG at BFM

"xeM" wrote in message
...
On Sun, 18 Jul 2004 21:32:18 GMT, "Chip Jones"
wrote:

[snipped]



Chip,

I think he must have been using Anywhere Map WX softare. One of the
way's it gets the Nexrad is via a Satphone. I think I remember a tech
note on their support page mentioning interference on the WX download
with certian King transponders. I bet he had one of those
transponders.


Ahh, I never thought of interference. Thanks.

Chip, ZTL

The King KT76A Transponder vs. Globalstar hand held sat phone issue is
a documented problem. Here is a link that explains the problem:

http://support.controlvision.com/kb/...ew/KB0078-0108

"Dan Luke" wrote in message ...
"Chip Jones" wrote:
The pilot calls my trainee and asks for permission to turn
off his transponder for five minutes so that he can "Go
download the latest weather".

Weird. Perhaps his transponder causes interference with his wx
receiver. If so, he *really* needs to get that fixed.