AHRS or GPS? An In-Depth Look at the GDL 39 3D

The GDL 39 3D is the latest addition to Garmin’s series of portable ADS-B receivers, which also offers the display of back-up attitude information within Garmin Pilot. While reading (and flying!) with the GDL 39 3D recently, I found myself wondering: how does a portable receiver display attitude, pitch, and roll information? So, it was time to get the books out. At power up, the GDL 39 3D performs an internal leveling adjustment so it does not have to be perfectly  level in order to display correct attitude information. Even if it’s not level, (and is situated on top of the glare shield in your airplane, for example) the GDL 39 3D is smart enough to calculate and compensate for this. What if you move it around in the aircraft after this adjustment has been made? No problem! The option to manually level the GDL is available by selecting ‘Menu’ and ‘Cage AHRS’ within Garmin Pilot, while in split screen mode. In an upcoming release, the option to select ‘Push to Cage’ will be available just below the attitude indicator within Garmin Pilot. Employing years of experience in developing certified Attitude and Heading Reference Systems (AHRS), the GDL 39 3D incorporates an internal Microelectromechnical systems (MEMS)-based AHRS, which utilizes the following sensors:

• 3-Axis Angular Rate Sensors: +/- 500 degrees per second
• 3-Axis Accelerometers: +/- 8G’s
• 3-Axis Magnetometer: +/- 2 gauss

Like Garmin’s popular portable GPS product line, the GDL 39 3D also utilizes GPS as an aid to obtaining track information. So, with the GDL 39 3D you’re getting the best of both technologies: MEMS and GPS-derived AHRS information, all conveniently displayed within Garmin Pilot. Okay, so I threw a lot at you for a Wednesday but the takeaway? The GDL 39 3D has a lot of features packed into a little portable device that offers pilots back-up attitude information within Garmin Pilot via a built-in AHRS, FIS-B weather, ADS-B traffic, and as if that wasn’t enough, it also has a built-in GPS! And the best part? Garmin’s not finished!