Radar spelled backwards is Radar

 I am working through my solo flight requirement the insurance company insisted upon.  Like the time with the instructor, I am trying to use the requirement to continue learning.  Today was a great day to work on radar skills.

Most people are are familiar with weather radar, stay away from the bright colors.  This is good advice but eventually you will need to fly in or near rain.  The trick is to avoid the severe weather and we have a variety of tools to accomplish this.  As you can see from the above picture, when I left today, it did not look like rain.

I have 3 sources of radar.  The first is broadcast via satellite using the XM radio system.  The second is sent via ground based transmitters and the final is an onboard doppler radar.  Interpreting all these pictures can be tricky.  The same image viewed on the panel screen has a different color coding when on the iPad.   I flew a good bit under the green area today and was not in any rain and the ride was smooth.  The picture is not wrong, it was just painting moisture at a different altitude than I was flying.

The two radars that are transmitted to the plane have the advantage that the picture is generated by the governments massive and powerful radars.  They also cover the entire country so I can see far, far away.  Also because the radars are a composite of many different antennas and their power, the chance that one storm can block the view of a storm behind its eliminated and you see a good picture of the actual precipitation.

It is not perfect though.  The ground based transmission you can't get while still on the ground so for the first few minutes you have no data from this source.  The bigger problem is that you are not looking at where the rain is, you are looking at where it was.  The picture is 5-15 minutes old by the time it gets to your screen.  Big picture this is fine but a fast moving storm could have moved 15 miles while you were waiting for the picture.  Also quickly developing storms can become severe before they evr show up on your screen.  That's why datalink weather is only good from strategic planning.

Airborne radar should solve all these problems except Physics.  The radars on the ground are huge, 28 feet across.  The dish in the airplanes nose is only 1 foot.  The NOAA radars have about 800 time the area and loads more power.  When you send out a radar pulse, the energy bounces off the rain and returns to be measured.  The more rain in the way, the more the energy is needed to see farther.  I have 40 Watts of power while the ground based units have 450,000 Watts.  Yes size matter.

Size matters not only for power but also beam width.  The radar is like a flashlight.  The further out it goes the wider the beam.  At 10 miles the core of my beam is 8000' wide.  That means it is 4000' above and below me.  At the full range of the radar (320 miles) the beam is 25 miles tall and wide.  In the picture above at 120 miles the beam is 18 miles wide.  What this means is that the farther out you go, your resolution suffers proportionally.

Sorry flat earthers, one more problem.  The earth is round.  Up close this does not matter much but at 100 miles, if you send your beam straight out, it is actually 7000 higher above ground because the ground has curved away from you.  Rain is basically visible from the freezing level down, ice does not reflect as well.  We compensate for all these issues by tilting the dish up or down to point the energy where we want it.  

One last problem, the ground is a great reflector so even on a clear day, the radar will paint what looks like storms but it will just be the ground.  Cities with their building look like bigger storms.  With all the problems, why bother?  Well if you practice a lot, you can learn how to direct that beam and understand what it is telling you.  The combination of old but very precise information with real time scanning of what you will fly through in the next few minutes is a powerful tool to avoid serious weather.

Having all those big screens means I can display the different sources how and where I like.  Above you can see the sky has gone from sunny to a dark wall.  Below I am watching datalink on the left and real time on the right,.  I am tilted up 4.5 degrees which eliminates most of the ground but the beam is above the farther rain and thus I am not painting any rain even though it is there.

One really cool feature is to overlay the live radar scan on the moving map.  While that looks really ugly, what you are actually seeing is the ground return, I had not yet adjusted the tilt.  Of course all this can get confusing.  If you display the radar on 2 screens it splits the back and forth scan and each screen gets one direction.  This way you can have 2 different settings at the same time.

After exploring the multitude of radar information, I turned around and made a quick gas stop.  Then it was back home before the storms arrived.