Originally Posted by
Airsupport
if that is how you are using the radar you are using it incorrectly. at fl300 the radar should almost always be in the negative tilt. the crj radar is actually pretty good, you just have to know how to use it.
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so in review.
Point radar so that you get a good solid arc of ground clutter at the furthest distance for the range you have chosen. the ground clutter should stay the exact same distance from you.
If something moves closer to you out of the ground clutter it is an area of weather and should be avoided.
I agree with your analysis that he is using it wrong but even your way of using it is incorrect. Well not incorrect, it will keep you alive but the return won't be accurate, it will overpaint weather. You will go around things you don't need to go around.
The goal of weather RADAR is to aim the beam somewhere between FL180 and 250 depending on who you listen to. David Gwinn says FL180. Archie Trammel says FL 250. Anyways. I use FL250 as a worst case "if I have to penetrate" level.
OK, how to aim it at that level?
Every 10 miles 1* of tilt changes the beam center by 1000' of your altitude.
What does that mean? If you want to aim it at FL250:
Q) You are at FL 250. Where should the tilt be?
A) 0* no matter what the range.
Q) If weather is 30 miles away and you are at 15,000, where should the tilt be?
A) Right around 3.2*. That will give you an accurate return on that weather.
Q) If you are on the ground departing on the 10-20 mile scale, where should the tilt be?
A) Anywhere from 10*-15*
The reason people think the RJ's RADAR "sucks" is because they don't know how to use it. We followed company the other day, 2000' below them. They didn't know how to use the RADAR and actually asked for a round about way around the weather in front of them that would've put them in a worse position because they were over painting a level 2 storm.
Landing in PHL the other day, ATC says "you'll go thru a level 3/4 return but the rides have been smooth, it's over the OM".
OK if this was really a level 3/4 return WE SHOULD NOT BE GOING THRU IT! It was a level 2 return.
For those who care the level 3 returns (red) start at 40 decibels. So compare your favorite online RADAR source with the 40 dbz returns and you can correlate what you are seeing out the window with what is being returned by ground based RADAR. The "red" on the NOAA/NWS site (
NOAA's National Weather Service) actually is a higher level red than you will see in the cockpit.
Not sure about other RJ's but the limit on the CRJ-200 RADAR dish is around 45 miles or so to depict an accurate VIP level at altitude. This is due to the pickup of ground clutter, which can clutter up the display.
For bonus points what's the quickest way to determine if you are painting a city vs. a cell in the distance?