Combined ADS-B/EFIS: Impressive Performers

The Stratus II is the top value but Sagetech’s Clarity SV leads in performance and features. But don’t rely on any of them for real backup.

If ever you harbored doubts that the iPad and its progeny would eventually be all things to all pilots, a herd of new ADS-B portable products last spring might erase them. No fewer than three new gadgets hit the market and we suspect more are in the wings. The “all things” part is that these new devices are equipped with functioning AHRS so the polymath tablet is now not just a navigator, but an EFIS, too.

So much for the glitter, but is the EFIS one you can really depend on? We’ll get to that in a moment. For now, suffice to say in this market, there’s a box for every budget and for under a grand, you get impressive navigational performance, FIS-B weather, limited traffic awareness and the EFIS, one version of which even includes synthetic vision.

For this review, we wrung out three ADS-B portables, the iLevil from Levil Technology at $1195; the Stratus II from Sporty’s/Appareo at $899 and, from newcomer Sagetech, the Clarity SV for $1400.

With $500 separating the top tier from the bottom, it’s natural to wonder if there’s that much value difference in features, given that all three units perform basically the same tasks. We’re not sure we can answer that, but we will say you’re not likely to go wrong with the cheapest choice. Now, on to the details.

Levil Technology is a small, family business in Florida that, oddly, specializes in desktop CNC equipment. As a sideline, the company has developed a series of aviation products including a pair of miniature AHRS products that output attitude information to other devices or directly to a smartphone or tablet via a wireless link.

The iLevil is the company’s first combined ADS-B/AHRS product. Like the other devices, it’s a self-contained, battery-operated unit that contains, in addition to the AHRS, single-channel ADS-B traffic (978 mHz) and WAAS GPS.

It’s designed to perch on the glareshield, where it can see both GPS satellites and ADS-B tower signals. Power is provided by an internal lithium-ion battery with about three hours of capacity, according to Levil. One quirky touch is that the iLevil has solar cells on top of its chassis, which the company says will extend the battery life to four hours. (We didn’t test battery endurance.) Charging time, via USB, is about four hours.

The iLevil measure 4 by 2.5 by 1 inch high and has a small whip antenna on one side for the ADS-B signal. While the other two products have gel mounting pads to secure them to the glareshield, the iLevil doesn’t, so a spot of Velcro will hold it fast. For the Apple iOS, the iLevil communicates via wireless protocol, but for Android, it uses Bluetooth.

We ran the iLevil with the latest iteration of WingX Pro and found the device takes about 20 seconds to find itself before shipping data to the app for display. On WingX Pro, the output appears as a basic PFD gyro with the standard blue-brown iconology, pitch and bank angle indicators and, along the top edge of the screen, GPS groundspeed, altitude and AHRS heading reference.

The display response seems accurate and relatively smooth, although it doesn’t have the damped-in-oil feel of a certified EFIS. The iLevil retains lock through steep turns and 360 degrees of roll, but give it quick shake by hand and it red-Xs. Ten seconds of straight and level recovers it. Levil says the iLevil’s max G rating is four, so we doubt if anything but the most severe turbulence will disrupt it.

The iLevil is single-channel ADS-B only, meaning it will receive FIS-B weather—NEXRAD, text weather, AIRMETS and so on—but only ADS-B traffic nearby that’s equipped with ADS-B Out and is communicating with a nearby tower.

Stratus II
Although SkyRadar introduced the first portable ADS-B in 2011, it soon got competition from device maker Appareo, which teamed with Sporty’s and ForeFlight to offer the Stratus. Introduced in 2012, the Stratus was a seamless wireless box with an internal battery that eliminated the wiring hassles with the SkyRadar. But it had no traffic and certainly no AHRS. Like Levil, Appareo is primarily an AHRS maker with products in the military and training markets, so it simply added ADS-B to its solid-state gyro expertise. The result is the second-gen Stratus II, which bears little resemblance to the launch product. At 6 by 2.6 by 1.25 inches, it’s the largest of the three with a form factor reminiscent of an early cellphone, with a weight to match.


Like the Sagetech Clarity, it has a gel pad mount, but all the antennas are internal. For those who wish to mount the Stratus away from the glareshield—not a bad idea to keep it cooler—the device has optional remote GPS and ADS-B antennas.

Once linked through the Stratus wireless network, the device sends position data via its WAAS GPS and attitude data via the onboard AHRS. However, rather than displaying through a navigation app such as ForeFlight or WingX, Stratus requires its own dedicated app called Horizon, a freebie from Appareo.

That means you have to toggle from one app to another to use it, so it’s not running in the background. Further, it works only with ForeFlight and the minimum recommended platform is the iPad2 or mini. Because it requires higher charging voltage, the Stratus has to be charged via line voltage through a provided USB cable and charger. Charging time is about five hours with a claimed eight-hour battery life.

The payoff of the dedicated app is that the display is larger and presents attitude data in a way that’s more consistent with panel EFIS design. GPS groundspeed and altitude are presented in tape displays and there’s also a vertical speed tape. Heading is via compass rose and there’s also a virtual turn-and-bank indicator.

The Horizon app offers some minimal manual calibration adjustments which its competitors don’t offer. For example, if you’re using Stratus in a taildragger, as we did, you can manually adjust the pitch on the ground to read straight and level once you’re airborne. Another button allows instantaneous straight-and-level calibration if you know you are and the unit thinks you aren’t. WingX provides this, too.

Dynamic response appears similar to the iLevil in pitch and roll, but one touch we liked was pitch warning chevrons. At 30 degrees of pitch up or down, the app displays red chevrons commanding corrective pitch inputs. Still, a quick shake will upset the AHRS lock, but it will recover in under 10 seconds.

For ADS-B, the Stratus II is dual-frequency—978 and 1090 MHz. That means like the iLevil, it will see ADS-B Out traffic talking to nearby towers, but it will also see 1090ES targets directly. Currently, there are more of the latter than the former, so dual-band or not, ADS-B is but a limited traffic solution.

Clarity SV
With its Clarity product, Sagetech is the newest arrival in the portable ADS-B realm and like Appareo, it leverages an extensive background in military and UAV technology as a trickledown to GA. Sagetech has two products, the basic Clarity, which offers dual-channel ADS-B ($1150) and the Clarity SV, which adds AHRS.

The Clarity SV wins the small form factor race and without really intending to, reveals how tiny and light the AHRS packages actually are. The Clarity SV measures 2.5 inches square by 1.5 inches high and weighs 5.5 ounces. The Clarity—without AHRS—has exactly the same dimensions. (Sagetech says the AHRS adds a mere gram to the weight.)

Springing as it does from the military UAV market, the Clarity has that dense, packed-with-tech feel you expect from military equipment. There’s no remote antennas, just an on-off button and a charging jack. The top of Clarity has a precisely machined grooved grid for heat rejection and the outer case is white, for the same reason.

Sagetech claims a battery endurance of six to eight hours with a charging time of four to eight hours, depending on the voltage used. It’s faster using the wall charger, slower using computer USB. Sagetech says the Clarity will correct for minor position errors on the glareshield, but it does need to be mounted facing forward. (This is true of the others, too.)

Using the Clarity SV with WingX in our Cub, we had to calibrate to straight and level in flight. For its higher price, the Clarity SV seems to deliver marginally better performance. Its dynamic response is somewhat smoother and while the other two products could be sensor saturated with a quick shake or two, the Clarity SV simply shrugged this off. Its GPS and ADS-B reception also appeared more robust; it easily tracked overhead 1090ES targets from inside a building.

The Clarity has a unique feature it calls Data Burst. If you let your iPad sleep during the cruise phase, it won’t be updated with current ADS-B data. The Clarity’s Data Burst feature catches everything up when the iPad wakes.

In evaluating any gadgets, we think it’s important to keep one’s feet wired to the ground with regard to capability. Portable ADS-B offers limited traffic awareness; you simply won’t see many if not most of the transponder-equipped targets around you. You will see most airliners, since they generally have 1090ES output.

ADS-B weather, while a nice-to-have, isn’t as complete or up-to-date as that offered by XMWX Satellite weather. But the price is right: it’s free. In our view, FIS-B-delivered NEXRAD is of limited utility for tactical weather decisions. Also, it can’t be received on the ground.

That leaves the AHRS function. All of the companies providing these products insist that they are for situational awareness only and haven’t been tested sufficiently to serve as a backup gyro in place of something that has been tested, such as an electrical, vacuum mechanical gyro or an electronic gyro. We agree. In one of our flights with the Clarity, WingX locked up and tanked completely. We had to land and update the app to bring it back. You can’t afford this sort of failure if you’re depending on a gyro for backup.

With these caveats, the Stratus II, at $899, is the best value of the group, in our view. It performs well, has adequate battery life and is we’ll supported. On the downside, it only works with one app and requires a separate app for the EFIS.

If cost is no object, we pick the Clarity SV as the best performer. We suspect its electronic innards are a cut above the competition, given its good GPS reception and resilience against sensor overload. Its small size is a plus.

The iLevil is certainly adequate, but its shorter battery life and single frequency ADS-B make it less competitive against the other two.

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Paul Bertorelli is Aviation Consumer’s Editor at Large. In addition to his valued contributions to Aviation Consumer, his in-depth video productions on sister publication AVweb cover a wide variety of topics that greatly contribute to safety, operation and aircraft ownership. When Paul isn’t writing or filming, he’s out flying his J3 Cub.