February 2005-
Next Generation Radar, NEXRAD, displays bring near time weather information to general aviation aircraft. Single engine aircraft safe operation takes a quantum leap when the pilot can look ahead and make routing decisions long before being surrounded by angry clouds.
I have used NEXRAD weather in conjunction with a Stormscope to avoid being in places I would rather not be. As long as the NEXRAD receiver works, then life is good and you and your airplane can stay out of trouble like the situation you see in the title picture above.
The first trip after my airplane’s 2002 Garmin 49 NEXRAD installation was right out of the textbook. Flying from New Orleans to Wichita, the forecast called for scattered light rain showers from Baton Rouge to west of Texas-Arkansas border.
We launched for Wichita and right on schedule near Baton Rouge rain streaks appeared on the windshield. As the little airplane on the moving map moved out of green areas, the rain stopped. When the little airplane moved, back into a green area rain pelted the windshield again. Life was good with this newfound weather detection aid.
Slowly the NEXRAD satellite downloads became erratic. Sometimes downloads stopped completely at the time you needed them in and around weather. Searching the Garmin website produced this piece of information:”Garmin GDL 49 receivers must be installed in a noise-free environment.” End of statement from Garmin with no further explanation.
Working with Kent McIntyre at Bevan-Rabell produced no direction either. The avionics shops were working in a brave new world and not getting a whole lot of help from Garmin. This is when I discovered that the Garmin operators were divided into two camps: those with GDL 49 receivers that worked as advertised, and others like me who did not have reliable NEXRAD downlink reception.
Bear with me because this story does have a happy ending as the cavalry, EchoFlight Support, comes over the hill to finally save the day.
If this story applies to you don’t let all the techno-speak later on in the article turn you off. Your avionics shop may be interested in the analysis and modifications done to achieve good NEXRAD reception.
System Analysis and Modifications
With Garmin’s advice, we started looking for noisy electrical components. The following steps helped but did not eliminate the NEXRAD reception problems:
• Install all Garmin Service Bulletins (“GDL 340 Audio Panel SB” is key)
• Replace ignition harness
• Install Zeftronics solid state plug-compatible Alternator Control Unit.
The new ignition harness seemed to improve reception considerably. However, there were times when reception was substandard for no apparent reason. Low orbit satellites transmit information to the Garmin GDL 49 receiver. The signals are very weak but the advantage of this system is that you can receive information on the ground or at any altitude.
Garmin designed the hardware and teamed with EchoFlight who wrote the receiver software, and manages the earthbound server and satellites. After paying for the aircraft-hardware installation, the money goes to EchoFlight for the duration of your GDL 49 operation for an annual service subscription.
Recently I came across the EchoFlight website and found a treasure trove of useful installation tips. Right on the first support page is a group of specific noise reduction recommendations. Digging around in the EchoFlight NEXRAD, receiver installation manual uncovered other items.
The combined list included:
• Install Version 2.04 software
• Install Alternator output filter
• Install Magneto P-lead filter
• Install Power line filter for GDL 49 power source
• Eliminate ground loops
• Insure static wicks have good electrical bond
• Install special antenna.
EchoFlight keeps performance data on your unit’s operation by date and flight for your review. Information shown is: response times, signal to noise ratio, and message size.
My unit’s response times were long and the signal to noise was low. My NEXRAD reception analysis results were not good.
I called EchoFlight support and talked to Carol Roehner. I had already installed version 2.04 software and magneto P-lead filters but signal to noise level was still low. I needed to add the other line filters. All three filters installed cost an estimated $400.
I mentioned to Carol that I did not have static wicks on the aircraft, but I did have them on the parts shelf. Oops, static wicks sitting on the parts shelf for five years do not help one bit reducing airframe P-static. I promised Carol that I would get them on the airframe ASAP.
During the annual inspection, we found a magneto P-lead ground loop. There were grounds on the P-lead to the magneto and at the switch in the cockpit. With the other two filter installations ordered from Lonestar Aviation complete all that was left were the static wicks and the Commant Special Antenna.
Reviewing the EchoFlight Performance Analysis reports showed significant improvements in signal to noise and shorter transmission times (less than yhree minutes.) P-static was still a problem in precipitation. The NEXRAD signal is so weak that P-static that is not audible in our headsets is enough to shut down satellite reception. After static wick installation, the GDL 49 receiver works as advertised.
With all of the above fixes installed EchoFlight saw no reason to recommend taking the last step to install the Commant special receiver antenna. These antennas are hand-built and tuned to the receiver bandwidth just above the normal VHF frequencies. This special antenna cost approximately $450 and Commant is very careful to offer no guarantees on solving GDL 49 reception problems.
Operation
The version 2.04 software upgrade changes Garmin NEXRAD operations dramatically with Automatic Weather Delivery. AWD eliminates aircraft generated requests. No longer do you send detailed messages on where your aircraft is with the type of request.
The EchoFlight server has the request profile that you have created when registering on their website. Your profile contains how many Graphic METARs and NEXRAD images per hour and coverage area (up to 250 nm) you want sent automatically to your receiver. On the Garmin 430/503 Aux page 4 is a Position report command.
During taxi out to the active runway, set the position reporting command to 15 minutes and then send a manual position report. The position report contains Latitude, Longitude, track, speed, and altitude. The EchoFlight server now knows where the aircraft is and transmits the Graphic METAR and NEXRAD weather to your aircraft.
Taxi to the active runway and perform your before-takeoff-check and your NEXRAD reports will normally be available before you leave the ground. EchoFlight states that the median request/response round-trip time for a normally operating system is about four-and-a-half minutes, with 85 percent of requests fulfilled in 10 minutes or less.
When using the Automatic Weather Delivery function this will also represent the age of the actual NEXRAD Imagery received. For this reason, Echoflight recommends requesting no more that four NEXRAD images per hour (every 15 minutes).
The reason for this is that the server gets all tangled up trying to sort out multiple requests from one receiver. When multiple requests build up in your personal queue then response time goes downhill in a big hurry.
I try to remember that this is near-time weather not a real-time weather receiver. If I am cutting it that close to weather in a 135-knot aircraft then I probably should not be there in the first place. Here is an EchoFlight benefit that can offer your family and friends peace of mind when you are flying. You have the option to email your position report information to 0-10 email addresses.
I send email position reports to Sara (my wife), and Kara (my daughter). They generally know when I am traveling to Denton or returning to Waltanna. The EchoFlight server translates the position report into an email message and emails the information.
Included in the email is a hyperlink to a sectional map displaying an aircraft symbol over the latitude/longitude in the message. With these 15-minute reports, Sara can track my progress and estimate my arrival at Waltanna.
Another use for this application is for VFR pilots traveling on cross-country flight. In the situation where a flight is overdue then there is a last known position at a known time and location for search and rescue to use in finding a lost aircraft.
Conclusions
There is no one silver bullet to improve avionics performance when you are chasing electrical noise. A step by step painstaking analysis is the only surefire way to make the Garmin GDL 49 receiver operate properly.
You may ask, “Why bother with all this effort when the Garmin GDL 69 MX receiver is ready to ship?” My response is how do you know that the new unit will operate without addressing the electrical noise issues? Is the new unit worth $5-6,000 additional investment with no trade-in for your current GDL 49?
Knowing how to operate the GDL 49 and special request make this a reliable weather unit that makes my flights safer. Another peace-of-mind benefit was demonstrated vividly on a trip right after the NEXRAD receiver installation. Sara and I were traveling from Kansas to Birmingham, Ala.
En route through Arkansas, NEXRAD was working as advertised and green, yellow, and red patterns were on the Garmin 430 display. The Stormscope showed activity that coincided with the red NEXRAD patterns and helped make us make course changes 50 to 100 miles in front of the weather.
Sara casually asked what the NEXRAD display colors meant. Sara is not a pilot but has worked in the aviation industry and has been a General Aviation aircraft passenger for years. So, she certainly can talk the talk.
I described that generally, green indicated light rain, yellow moderate rain, and red correlated with Stormscope dots means don’t go there.
Later in the trip NEXRAD stopped working near some moderate weather and our discomfort level increased significantly deciding how to deviate around the weather. At this point Sara calmly stated, “Charles, NEXRAD is a no-go item.”
I protested weakly by saying, “Hey, what do you mean, we have flown for years with nothing and then a Stormscope before we ever had NEXRAD.”
Sara’s reply was, “Now that I know what NEXRAD can do to help us avoid weather, it is a ‘No Go’ item”—stated in a “this is the end of this discussion” tone.
To which I could only reply, “Yes, dear.”
The key is a passenger’s peace of mind in flying in the clouds is significantly higher when you open up the NEXRAD weather picture window to them. Sara is a more relaxed passenger with NEXRAD on board.
Finally, the support received from EchoFlight Support to lead me through the performance analysis is what finally made this GDL 49 receiver finally perform to specification. I cannot say enough good things about EchoFlight Support and Carol Roehner’s technical knowledge, patience, and humor in helping resolve these technical problems.
References
EchoFlight
www.echoflight.com
EchoFlight Support
https://www.echoflight.com/support-public.asp
Lonestar Aviation Filters
https://www.lonestaraviation.com/
Comant NEXRAD Antenna
https://www.comant.com/htmls/ci177_4.html
Zeftronics
www.zeftronics.com
Charles Lloyd has logged 7,900 hours since his first flying lesson in 1954. He worked for Cessna Aircraft in Citation Marketing and Finance for 16 years. Charles’ current day job is as a Citation Excel Captain for a major fractional aircraft ownership company.
