Monday, March 15, 2021

Nexrad and Onboard Radar

The following article appeared in the March 2021 issue of the American Bonanza Society magazine - www.bonanza.org

At least once a year, I come across a Baron I haven’t flown before, equipped with an old monochrome magic box that hasn’t been turned on in 20 years - only to have emitted electrons when the pilot accidentally turned it on. 

In the world of ADS-B, high resolution Nexrad Radar and all kinds of goodies on my tablet, why in the world would anyone care about onboard radar?  This is actually a common sentiment I hear from pilots when I ask if their radar works, or whether they use it. Most of the time they do not use it, and that is ok.  For most pilots, navigating a line of weather, or radar with green returns will convince the casual flyer to stay on the ground. But what about the avid IFR pilot getting maximum utility out of their Baron?  Do THEY use their Radar? Do they even have radar?

With advancements in technology, many are investing in their panel and quite frequently, the old radar gets yanked out (which is great for useful load), and not replaced (the expense of installing new onboard radar is still high).  The magic of XM Satellite weather, and the affordability of FIS-B weather (can you say free?) is exciting many pilots with more tools than we have ever had before.  Again, this is not a problem, but begs the question – is the pilot using the digital imagery to tactically navigate weather or is it being used for planning and big picture strategy? There is a difference.

When to use Nexrad

The trap comes when pilots try to navigate weather using Nexrad.  This goes for Bonanza pilots too.  Why is this an issue? It comes down to the delay of information and is the reason pilots must only rely on Nexrad for strategic weather planning and not use it for tactical weather decisions. Many get suckered into thinking that the Nexrad Age showing only 3 minutes is indicative of near-real-time conditions.  It was explained to me by an old acquaintance from the National Weather Service that when a radar mosaic is compiled, it takes multiple scans of the radar site to compile the image, he joked that a bunch of interns take their time to stitch it all together, then it is disseminated for distribution.  I’m sure this process is automated, and professionals are involved in creating the mosaic, but his point is that it could easily take 10 minutes or more before the image gets shipped out to the providers. While XM Weather boasts imagery that is no older than 5 minutes because of where they get the data and how they process the radar images, the contrast in imagery versus what I typically see out the window seem to indicate there may be more of a delay than they claim.  The delays with this whole process are real – so much so that the NTSB came out with an advisory that talks about the delays associated with this process:

https://www.ntsb.gov/safety/safety-alerts/Documents/SA_017.pdf

It goes without saying – Nexrad radar images are to be treated as what happened (past tense) and not an indication of what IS happening. A good example of this are the pictures to the left. The Nexrad image (XM satellite – Age of 3 minutes) showed a yellow return just ahead and to the left of our nose.


Since we were visual, we could clearly see that the rain shower was in front and just to our right! If you look closer, you can also see what the red returns out in the distance look like.

When you need onboard Radar

The simple answer is that you need onboard radar for navigating weather and making tactical decisions.  However, just by having onboard radar doesn’t mean you are equipped to go blasting through cold fronts navigating convective activity. You need the training in order to use these boxes. The beauty of datalink weather is that there is nothing to do but watch the screen – with onboard radar this conversation could take on a life of its own as a college course.  And maybe that’s why there is frustration, confusion and proverbial throwing the hands up at the situation.  The good thing is that in this day and age, there are so many resources on the internet to help with understanding how to use your onboard radar, and you aren’t relegated to watching an old VHS tape of Archie Trammel – the radar God of yesteryear. Come to think of it – I think I still have that VHS tape.  It was considered gold at the time and many of the concepts Archie introduced are still valid today.

Some of the buttons and knobs seem to have a friendly feel to them.  Range – seems obvious. Distance you want to scan.  Tilt – At what angle do you want to focus your radar.  There might be gain controls, hold buttons, and other buttons that seem intuitive.  This is all well and good, but as I mentioned above, a solid course in radar use is a must if you are going to be making tactical decisions with it. 

More than just Radar and Nexrad

The screen to the left depicts one afternoon when I was flying a quick trip to KCMI.  Because Nexrad shows the whole sky, it paints a picture of rain and potential building convective activity.  But does it?  That trip was flown at 6,000ft – in the clear the whole time with cloud bases at 8,000ft with

occasional virga.  Onboard radar would have given me the confidence to fly this trip, but I wouldn’t have a completely full picture of the situation.  So, how did I know the trip would be fine?  It was all about the pre-flight weather briefing and understanding weather.  I knew that this moist airmass was not associated with a front, and a check of the ground-based reporting stations revealed high ceilings. A thorough preflight review of the current weather and trends are key to successful weather planning. 

Conclusion

Many seasoned Baron pilots reading this article may feel this is basic information, but frankly, there are a lot of individuals stepping up to a Baron that don’t have this experience and might be oblivious to the perils of datalink weather, the merits of onboard radar, and might have had frustrating experiences with either of these weather tools.  A rash of conversations at the local FBO as well as at least two posts on one of my favorite Beechcraft forums reveal that there are both Baron and Bonanza pilots relying on datalink weather for tactical decision making while airborne, which could have disastrous consequences.  An evaluation of the kind of flying you are doing (or want to do) coupled with some focused sessions with a BPPP instructor that has expertise with these systems will go a long way in helping you get the most utility out of your Baron.