We are all looking at January 2020 and wondering how we are going to comply with the requirements to install ADS-B equipment without going broke in the process. As experimental owners and builders, we have more flexibility than certificated owners, but until recently most of the equipment that we could consider was rather expensive. Then at AirVenture 2017, Garmin introduced the GDL 82, a modestly priced ABS-B Out box that could meet the upcoming FAA requirements without installing a pricey Mode S transponder. This would be paired with a GDL 39R In box to receive weather and traffic. People with existing glass panels and/or Mode S transponders will have other options, but for me and many others with older equipment, this represents a robust and not-too-expensive solution to the upcoming requirement.
Here are all of the parts needed for the installation plus the manuals downloaded from the Garmin website. A few antenna connectors are missing, which resulted in a delay of the installation.
The problem was that Garmin was ready to take orders but not ready to ship these units. This would not be of any great concern except for the possibility of qualifying for the FAA $500 rebate program, which required a signup in September of last year and an installation of not more than 150 days after that—in other words, installation by early February. A promised ship date of November slipped into December and then January, with my unit finally arriving on January 24, less than three weeks before my drop-dead date of February 9. Theoretically that is plenty of time, but it was cutting it pretty close.
Besides actually installing the unit, a performance report must be issued by the FAA to qualify the unit for service and the rebate. It took a few tries to get the FAA website to accept my flight information and send me a performance report, but it finally came through. My first attempt got flagged because I entered the Mode S code improperly, but I got that fixed and the final report came back clean.
Of course, for anyone reading this article, the rebate program is no longer a factor. The signup and installation dates have now long passed, but January 2020 is still coming up before you know it, and the requirement for most people for ADS-B is not going away.
Installing the two Garmin boxes was not difficult, although I tried to make it harder than it should have been. I switched the transponder in and out leads with my first try, which rendered the system completely inoperative. Luckily the cables I had made were long enough to overcome my initial ineptitude, so the fix was quickly executed once I figured out what I had done.
A cardboard template was used to cut and bend a mounting tray for the two Garmin units. Some Adel clamps held the tray in place.
The boxes mount remotely and require no user interface to operate once they are set up. It was just a matter of finding the space and making the mounting tray. Besides the antenna leads, the units only need power to operate, so wiring is a snap. On the GDL 82 box there is an input for the cable from your existing transponder and an output to your existing transponder antenna. These are BNC connectors. There is also an input for a GPS/WAAS antenna. This is a TNC (threaded) connector. Lastly, there is a 15-pin connector that in my case was only used for power and ground.
With a brake and shear it was quick work to make a mounting tray from some scrap aluminum. This work could be done without this equipment, but it would be a little harder.
The GDL 39R box is even easier to install. There is a connector for the ADS-B antenna, which is essentially a transponder antenna. This is used to receive the ADS-B In signal that has traffic and weather information. There is also a separate GPS antenna input for an antenna that is included with the unit. Lastly there is a 9-pin connector that I again only used for power.
he two Garmin boxes fit neatly into a tray that mounted under the seat. This works, in part, because the user has no need to directly interface with the avionics to operate them after installation.
The GDL 39R communicates its information to the pilot through a Bluetooth connection to a tablet (not included). In my case I used my iPad with ForeFlight for the display. Because of the age of my avionics, I was not able to display the ADS-B information on my Apollo MX20, but the iPad works reasonably well as a substitute.
I made a tray from some scrap aluminum I had in my hangar and placed the two boxes on it under the copilot seat. There is nothing special about this location except that it happens to be unobstructed and has good access to the various antennas that must be connected to the unit. It was also easy to run the power and ground leads back to the instrument panel from there. I had a spare breaker and a spare hole on the ground bus for the required power wires, so this worked out very well. It is your choice as to whether you get power from an avionics bus or the main bus.
A ground plane roughly 6 inches in diameter improves the performance of the ADS-B In antenna in planes with composite fuselages such as the Sportsman. The 90-degree connector added cost but made it easier to keep the antenna wire away from the rudder and elevator cables.
Once the boxes were installed and powered up, it was time to program the GDL 82. The installation program was available from Garmin and went easily onto my laptop. I assume that it would also work with an Apple laptop, but I did not research that to verify compatibility. The GDL 82 connects to your laptop with a USB printer cable (not provided). I left the cable in place and secured it for future use just in case. As it turned out, I was glad I did.
A plate was fabricated to hold the extra GPS antennas required by the two Garmin units. With the composite fuselage we were able to keep them inside the airplane.
There are a few pieces of information you will need to program the GDL 82, the main ones being the serial number of the unit and your plane’s Mode S code. The Mode S code can be found in your registration file with the FAA. This can be easily accessed by doing a search for your tail number. The code is listed in two formats—decimal and hex. You can use either one, or there is an automatic lookup function that uses your tail number. The lookup function will not work if your laptop does not have a working Wi-Fi or LTE (cell phone) connection. Avoid problems by getting this information first. Once all the required data is entered, be sure to save the file on your laptop for future reference.
A laptop is needed to program the GDL 82, but the program is easily downloaded from the Garmin website, and the setup programming takes only a few minutes if you have the Mode S code and serial number for the GDL 82.
If you are organized and have all of the required parts, wires, and connectors at hand, these units can be installed in one day, or certainly one weekend, for most planes. For those of us that did not have the proper connectors on hand, the installation ran over into two weekends. I had mistakenly assumed that Aircraft Spruce would have all the connectors I needed in stock, but they didn’t. Thus, the delay.
Two things make this installation quite simple. One, you get to keep using your old Mode C transponder in most cases. And two, there is no need to wire into your existing avionics for the GPS signal, nor is there a requirement to even have a GPS/WAAS receiver in the plane. This not only makes things pretty easy, it also saves a lot of money for VFR pilots who don’t need GPS/WAAS equipment.
Connecting the GDL 39R to my laptop was a snap. ForeFlight has everything built in to the program to make the Bluetooth connection and link the information to your display. One thing I did notice is that displaying the traffic information over the sectional display made it almost impossible to read. I switched to the aerial photo view in ForeFlight for better readability.
The last step of the installation process is to go fly for at least 30 minutes in an area with good ADS-B ground coverage. There is a map available online if you are not sure about the coverage in your area. Once you have flown, you will need to request a performance report at a special website set up for this purpose.
Here are how my costs broke down:
- Garmin GDL 82: $1,710
- Garmin GDL 39R: $750
- Antennas and cables: $426
- Total: $2,886
This assumes no cost for labor. I would guess that if you paid someone to install the equipment for you, it would add somewhere around $1,000. If you built the plane yourself, this would likely not be a consideration, but a non-builder owner might want to take advantage of some professional help.
The iPad mounts conveniently on the right side of the instrument panel where it gets traffic information from the GDL 39R via Bluetooth. With ForeFlight set to display the sectional, traffic is very difficult to read.
How it Works
The Garmin GDL 82 operates on the UAT (978 MHz) frequency. This is the lowest-cost option for most people, but it has its downside. UAT is only good in the United States and only below 18,000 feet. If you travel to Canada, Mexico, or the Caribbean, or above 18,000 feet, the more expensive 1090ES option will be better for you. The 1090ES option will require a new transponder for anyone currently using a Mode C unit. If you have a Mode S unit, you may be able to upgrade it to an ES model and meet the ADS-B out requirement. If you are in the decision-making mode it would be a good idea to talk to your favorite avionics vendor and see what makes the most sense with your flying situation and current installed avionics.
With ForeFlight set in aerial map mode, traffic shows up much better. Glare is something of a problem with the iPad, but it looks worse in this photo than in actual use. Keeping the iPad plugged into power at all times ensures that the display will stay on for the entire trip.
The GDL 39R receives signals on both frequencies and from grounds stations. This ensures that all ADS-B and transponder-equipped aircraft will show up on your traffic display. It also gives you the weather information from Nexrad that you want at no monthly cost. I have not yet had time or the opportunity to work with the weather display—mainly because Southern California hasn’t had any weather lately. After a couple of inches of rain early in January, we decided to cancel winter this year and get back into drought mode. Hopefully some interesting weather will come around eventually so I can see what it looks like.
The Bottom Line
As an airplane owner with equipment that is now 12 years old, and as someone who was not yet ready to plunk down $15-20,000 for a major panel upgrade, the Garmin GDL 82 and GDL 39R made a lot of sense to me. With a Garmin product you will likely not be getting the cheapest solution, but it will be well-engineered, well-built, and well-supported. To me that is worth something.
If I were looking at a new panel right now, I would have more choices in front of me and might make a different decision. Certainly, as my current GlaStar project nears that stage, I will need to do some more research. However, for owners of existing airplanes this seems like a good solution to meet the upcoming ADS-B requirement. I could have waited another year, but the rebate got me motivated to do something now, and the traffic information is very nice to have in the busy airspace of Southern California where I do most of my flying.