Allthway,
There is one main theory behind weather RADAR use from several industry experts. Archie Trammel was a pioneer for airborne RADAR, his material has already been touched on here. David Gwinn is also another, he worked for Honeywell I believe. There was a PDF posted above from someone else at Honeywell, and its principles are the same yet it has a distinct difference in it which I'll touch on in a bit (and argue against).
Here's some background, I'll try to not confuse you, and start from the top:
There are several VIP levels that "paint" on RADAR. Keep in mind this is just precipitation, normally rain. It's generally accepted that the higher intensity the precip, the higher intensity the storm, right? We are taught to avoid the reds and magentas.
What "they" don't tell us is that the level 1, 2, 3-4, and 5-6 levels with corresponding colors of green, yellow, red, and magenta are actually calibrated for returns at the FL 180 to FL 250 level. In other words, a red return you see on a government chart that would really correspond to a level 3 (or "severe") in normal everyday use will paint red at FL 180 thru FL 250. This is important; keep that in mind while I tell a little story.
I'm a regional FO. I had no formal training in weather RADAR use except "Don't go into the reds!" and playing around with it in a Baron. That was basically it. OK, I can deal with that, it sounds easy. Anyway, one day on an approach into White Plains, a nice red storm sat over the FAF. "This RADAR sucks!" the Captain said, as he turned the gain down. "Ah, that's better!" - it was only showing a moderate return now. It's not red.we can go thru."OK, sure, whatever" I said. The same thing happened in Charlotte a few days later, except he just said the "RADAR sucks" and is "too sensitive" up close. We went thru, as did everyone else that night. No problems with storms, just heavy rain.
Why were these returns painting red but not really a dangerous storm? It sounded like the boy who cried wolf scenario to me, an accident waiting to happen. Red is OK sometimes.but not others? Huh?
What was going on is that the tilt of the RADAR was too low. The energy required to lift precipitation to a 50 dbz return (a "magenta" or level 5-6 return) to 10,000' isn't anywhere near the energy required to lift it to FL 250. IOW, a return at around 10,000' painting red really isn't dangerous. It might be bumpy, wet, or both, but it's not going to bring the plane down. One painting red at FL 250 is dangerous, however.
So, the question is, how do you find returns at the FL 180 - FL 250 level and see if they are dangerous? Use the tilt.
Every degree of tilt raises the beam 1000' per 10 miles out. For example, tilt up 1 degree, and at 10 miles the beam width goes up 1000'. At 40 miles out, it's 4000'. OK, once you've mastered that let's move on.
You're level at 10,000'. There is a cell 40 miles in front. The objective is to aim the center of the RADAR beam into that storm somewhere in the FL 180- FL 250 area. I generally use FL 200 as my point. So, we need to tilt up 10,000'. That's 2.5 degrees up. 2.5 x 40 = 10, or 10,000 ft. Simple. Now, is the return red or magenta? Yes? Don't penetrate. Simple as that.
You're high. FL 300. There is a cell 30 miles away. Lower the tilt to -3.0 degrees. If it's red, go around!
The problem with this method, and with small airborne RADARs, is they are limited in range. A smaller CRJ-type RADAR can only *accurately* paint within 40-50 miles. Anything outside of that will be mixed with ground clutter or the tilt will be so high you won't be centering at the FL 180 to FL 250 level, and you'll aim above that. That's what happens when you are in embedded stuff and it "comes out of nowhere". I remember a particular flight where the CA was pissed because nothing was painting yet we were getting rocked. It's cause he had the tilt up at something like +3.0 at FL 300, completely skipping the "meat" of the storm.
As long as you know that limitation, you will be OK. You can use it outside of the technique described here, but just remember to return it to that FL 180 - FL 250 level to investigate further. Also, if you are in, say, Denver, consider boosting the gain +1 in order to give an accurate return, as those storms are dry (I found out the hard way.once.). In Florida, consider Gain -1.0, as those storms are extremely wet. For most of the country, however, Gain 0.0 works well.
Another thing - using this technique you realize that on departure, you really can't see squat. Even at 10 miles away from the field, sitting on the ground, you can only see up to the 15,000 level (+15.0 tilt max) above field elevation. There was a Delta crash, in Texas, sometime in the 1980's where they hit a microburst. What happened is their beam was so low that they didn't see there was actually a large storm in front of them, they were just painting weak or moderate returns. It was just a limitation of their altitude, and their distance to the storm.
This technique won't guarantee you avoiding turbulence, but it will keep you alive.
---------------
Now, for the differences in the above posted PDF. That gentleman argues that the beam should be centered in what looks like the 9000' - 15,000' level. This report is fairly new, however I will say that Archie and David, as well as Honeywell in 2000, have stated use the FL 180 to FL 250 level as an indicator. I'm not sure where this person got this research from; I'd be interested in finding out more about his numbers.
There is one main theory behind weather RADAR use from several industry experts. Archie Trammel was a pioneer for airborne RADAR, his material has already been touched on here. David Gwinn is also another, he worked for Honeywell I believe. There was a PDF posted above from someone else at Honeywell, and its principles are the same yet it has a distinct difference in it which I'll touch on in a bit (and argue against).
Here's some background, I'll try to not confuse you, and start from the top:
There are several VIP levels that "paint" on RADAR. Keep in mind this is just precipitation, normally rain. It's generally accepted that the higher intensity the precip, the higher intensity the storm, right? We are taught to avoid the reds and magentas.
What "they" don't tell us is that the level 1, 2, 3-4, and 5-6 levels with corresponding colors of green, yellow, red, and magenta are actually calibrated for returns at the FL 180 to FL 250 level. In other words, a red return you see on a government chart that would really correspond to a level 3 (or "severe") in normal everyday use will paint red at FL 180 thru FL 250. This is important; keep that in mind while I tell a little story.
I'm a regional FO. I had no formal training in weather RADAR use except "Don't go into the reds!" and playing around with it in a Baron. That was basically it. OK, I can deal with that, it sounds easy. Anyway, one day on an approach into White Plains, a nice red storm sat over the FAF. "This RADAR sucks!" the Captain said, as he turned the gain down. "Ah, that's better!" - it was only showing a moderate return now. It's not red.we can go thru."OK, sure, whatever" I said. The same thing happened in Charlotte a few days later, except he just said the "RADAR sucks" and is "too sensitive" up close. We went thru, as did everyone else that night. No problems with storms, just heavy rain.
Why were these returns painting red but not really a dangerous storm? It sounded like the boy who cried wolf scenario to me, an accident waiting to happen. Red is OK sometimes.but not others? Huh?
What was going on is that the tilt of the RADAR was too low. The energy required to lift precipitation to a 50 dbz return (a "magenta" or level 5-6 return) to 10,000' isn't anywhere near the energy required to lift it to FL 250. IOW, a return at around 10,000' painting red really isn't dangerous. It might be bumpy, wet, or both, but it's not going to bring the plane down. One painting red at FL 250 is dangerous, however.
So, the question is, how do you find returns at the FL 180 - FL 250 level and see if they are dangerous? Use the tilt.
Every degree of tilt raises the beam 1000' per 10 miles out. For example, tilt up 1 degree, and at 10 miles the beam width goes up 1000'. At 40 miles out, it's 4000'. OK, once you've mastered that let's move on.
You're level at 10,000'. There is a cell 40 miles in front. The objective is to aim the center of the RADAR beam into that storm somewhere in the FL 180- FL 250 area. I generally use FL 200 as my point. So, we need to tilt up 10,000'. That's 2.5 degrees up. 2.5 x 40 = 10, or 10,000 ft. Simple. Now, is the return red or magenta? Yes? Don't penetrate. Simple as that.
You're high. FL 300. There is a cell 30 miles away. Lower the tilt to -3.0 degrees. If it's red, go around!
The problem with this method, and with small airborne RADARs, is they are limited in range. A smaller CRJ-type RADAR can only *accurately* paint within 40-50 miles. Anything outside of that will be mixed with ground clutter or the tilt will be so high you won't be centering at the FL 180 to FL 250 level, and you'll aim above that. That's what happens when you are in embedded stuff and it "comes out of nowhere". I remember a particular flight where the CA was pissed because nothing was painting yet we were getting rocked. It's cause he had the tilt up at something like +3.0 at FL 300, completely skipping the "meat" of the storm.
As long as you know that limitation, you will be OK. You can use it outside of the technique described here, but just remember to return it to that FL 180 - FL 250 level to investigate further. Also, if you are in, say, Denver, consider boosting the gain +1 in order to give an accurate return, as those storms are dry (I found out the hard way.once.). In Florida, consider Gain -1.0, as those storms are extremely wet. For most of the country, however, Gain 0.0 works well.
Another thing - using this technique you realize that on departure, you really can't see squat. Even at 10 miles away from the field, sitting on the ground, you can only see up to the 15,000 level (+15.0 tilt max) above field elevation. There was a Delta crash, in Texas, sometime in the 1980's where they hit a microburst. What happened is their beam was so low that they didn't see there was actually a large storm in front of them, they were just painting weak or moderate returns. It was just a limitation of their altitude, and their distance to the storm.
This technique won't guarantee you avoiding turbulence, but it will keep you alive.
---------------
Now, for the differences in the above posted PDF. That gentleman argues that the beam should be centered in what looks like the 9000' - 15,000' level. This report is fairly new, however I will say that Archie and David, as well as Honeywell in 2000, have stated use the FL 180 to FL 250 level as an indicator. I'm not sure where this person got this research from; I'd be interested in finding out more about his numbers.
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