GDL-49 and Levels of Radar Returns

Tim,

Chapter 1, section 1 of the AIM would seem to be most appropriate for
this question, and I have found no references to radar echoes. If you
have a pointer to the information that you think answers my question,
that would be helpful.

Please forgive my ignorance, but I do not know the acronym "IHB."
Please expand.

I have also tried Circular AC-00-6A, and did not find it.

I would also note that note of these sources is likley to answer the
questions of color mapping on a GDL-49/Garmin 430.

-Sami

wrote:


"O. Sami Saydjari" wrote:


As I was coming into Grand Rapids (KGRR) yesterday, the controller
announced that there was a "level 5" return (or perhaps she said "cell")
on final to runway 8, so I was vectored to 35 where there were mostly
"just level 4" stuff. So, forgive my ignorance, but where are these
levels defined? I assume they have to do with what sort of radar return
they get off a cloud and therefore has to do with rain intensity. Does
a level 5 return imply that a thunderstorm is likely to be generating it?

Also, I have a GDL-49 Satellite Data Link Transceiver linked to my
Garmin 430 display. I understand (and now have seen) that these things
just are not adequate to locate big cells. Rather, they show large
areas of showers. Are these based on satellite imagery, or from
aggregated ground station data or what?

Also, how to the radar levels (1 thru 6?) relate to the colors shown on
a GDL-49 display on a Garmin 430? Does red equal level 5 or level 6? I
think only have red, yellow and green...so it seems there are not
enough colors to show 6 levels.

-Sami, N2057M, Piper Turbo Arrow III


You might try checking the AIM, for starters. Then, perhaps, the IHB.

"O. Sami Saydjari" wrote:

Tim,

Chapter 1, section 1 of the AIM would seem to be most appropriate for
this question, and I have found no references to radar echoes. If you
have a pointer to the information that you think answers my question,
that would be helpful.

Please forgive my ignorance, but I do not know the acronym "IHB."
Please expand.

FAA Instrument Handbook



I have also tried Circular AC-00-6A, and did not find it.

I would also note that note of these sources is likley to answer the
questions of color mapping on a GDL-49/Garmin 430.

That is Garmin's responsibility to explain what their equipment does and
presents. Having said that, a pilot cannot be expected to assess the levels of
intensity to the same degree of discernment that a severe weather expert
sitting at a desk with a giant NEXRAD display does.

Green, yellow, and red where chosen for color radar displays based on the same
human factors used for traffic lights, and other safety signals.

Some folks used monochrome radar displays very successfully for many years.

Start by doing a search on "Radar VIP level". Basically VIP levels measure
reflectivity and go from 1 to 6. Anything from 3 on up is probably a
thunderstorm in North America although in the tropics you can get level
three without a thunderstorm. A level 5 is considered an "extreme" echo.
Your Garmin displays a VIP 5 as orange. A level 5 echo will produce about
6-8" of rain per hour (I forget the exact figure) so you are looking a a
"wrath of God" type storm and if you fly in the side you will probably come
raining out the bottom in little pieces There are a lot of general
observations like "a level five echo in FL will probably be less severe than
a level five echo in the Great Plains", but since these observations always
include a "probably" they are not too useful. Some pilots think that they
can tell the level of a thunderstorm by looking at it, they are idiots.

Mike
MU-2

"O. Sami Saydjari" wrote in message
...
Tim,

Chapter 1, section 1 of the AIM would seem to be most appropriate for this
question, and I have found no references to radar echoes. If you have a
pointer to the information that you think answers my question, that would
be helpful.

Please forgive my ignorance, but I do not know the acronym "IHB." Please
expand.

I have also tried Circular AC-00-6A, and did not find it.

I would also note that note of these sources is likley to answer the
questions of color mapping on a GDL-49/Garmin 430.

-Sami

wrote:


"O. Sami Saydjari" wrote:


As I was coming into Grand Rapids (KGRR) yesterday, the controller
announced that there was a "level 5" return (or perhaps she said "cell")
on final to runway 8, so I was vectored to 35 where there were mostly
"just level 4" stuff. So, forgive my ignorance, but where are these
levels defined? I assume they have to do with what sort of radar return
they get off a cloud and therefore has to do with rain intensity. Does
a level 5 return imply that a thunderstorm is likely to be generating it?

Also, I have a GDL-49 Satellite Data Link Transceiver linked to my
Garmin 430 display. I understand (and now have seen) that these things
just are not adequate to locate big cells. Rather, they show large
areas of showers. Are these based on satellite imagery, or from
aggregated ground station data or what?

Also, how to the radar levels (1 thru 6?) relate to the colors shown on
a GDL-49 display on a Garmin 430? Does red equal level 5 or level 6? I
think only have red, yellow and green...so it seems there are not
enough colors to show 6 levels.

-Sami, N2057M, Piper Turbo Arrow III


You might try checking the AIM, for starters. Then, perhaps, the IHB.