Datalink WX for iPad: ADS-B is a Better Deal

Baron’s Mobile Link system for XM weather offers more feature-wise, but ADS-B gives you all the critical stuff for less cash and complexity.

The iPad cockpit revolution has been slow to incorporate data-link weather. Many iPad fliers take their downloaded weather from the FBO and work with that, what 3G they can get in the air and calls to Flight Service.

Datalink weather for the iPad via ADS-B has actually been around for a while (“Portable ADS-B WX,” May 2011 Aviation Consumer), but limited coverage and limited pilot acceptance has mean limited equipage. Now that Baron Services, who supplies the XM weather service to XM/Sirius, has entered the iPad age with their Mobile Link will datalink sweep the iPad universe?

We don’t think so. The Mobile Link system works well, and is a smart choice for a select group of users. But we think ADS-B solutions are a better choice for the majority. Which group you’re in depends on your exact situation, and possibly, which iPad app you prefer.

From Satellite to iPad
Datalink weather for the iPad is a two-part solution. There’s new hardware to download the weather data and get it to the iPad and then the app you’re using to view that weather data. For XM weather downlinked from the XM satellite system, there’s only one hardware option: Baron’s Mobile Link coupled to an XM portable receiver.

Baron has long had a portable XM weather solution that has been used to push weather to various laptop computer systems and portable GPS units such as the Bendix-King AV8OR series. The Mobil Link is actually a second black box that takes the signal from that XM receiver and broadcasts it on WiFi to connect to the iPad. This means the complete hardware solution is two boxes (connected by a cable), two remote antennas (one for GPS position and one for reception of the XM satellite signal and a power cable (one cable can power both units).

This strains the definition of the term “portable” and probably isn’t practical if you’re jumping between different aircraft. However, because the iPad connects via WiFi, the whole system can be buried in the baggage area or under a seat so long as the antennas can get to a window and power can reach the cigarette plug. The supplied cables were amply long to do this in our test aircraft.

Once the system is running, it’s a matter of kicking the iPad into airplane mode and then turning back on the WiFi. A network called “MobileLink” will appear. Connect to that network and the app will do the rest. As of this writing, XM weather is supported by ForeFlight and Global Nav Source. WingX and Flight Guide’s iEFB should have XM support in the first quarter of this year.

The app is an important part of the equation. For example, ForeFlight, which we used for most of our testing, currently supports XM METARs, TAFs, PIREPs, TFRs, winds aloft, AIRMET/SIGMETs, NEXRAD and satellite images. This includes Canada if your XM subscription includes it. Other data in the XM stream, like datalink lightning and Current Icing Potential, are available, but ForeFlight doesn’t yet support them. There’s also no XM radio streaming. Oddly, the XM receiver has WAAS GPS position but doesn’t pass this to the iPad. You’re stuck with the iPad’s internal GPS or a separate GPS receiver for your moving map.

ForeFlight does an excellent job of seamlessly weaving the XM information into its existing user interface. It’s long offered radar overlaid on a map, but now it will use XM NEXRAD whenever it’s available. The same is true for METAR/TAFs. If XM is available, you’ll get XM data. If not, you’ll see the most recent internet data. Either way, the source and timestamp is available so you know where it came from and when. A nice recent addition to ForeFlight has been PIREPs on the moving map. These work with both internet and XM PIREPs.

One thing we found disconcerting is that if you’re in flight and try to display XM NEXRAD when the data isn’t available, ForeFlight blanks out the entire map. While you won’t mistakenly think there’s no rain when there’s actually no data, we think that notification is a bit extreme.

ForeFlight provides a good interface to check XM reception status and data latency. This can be handy on certain headings where the antenna can get blanked by a wing or seat. The XM satellites are both in the southern sky for U.S. users. It can be a bit persnickety if you change apps in flight, but we were always able to get it to reconnect with some futzing.

The complete system of a XM receiver for portables and the Mobil Link to drive that data to the iPad is $1124. If you already have an XM receiver for portables, you can buy the Mobile Link Wi-Fi box for $200 to add on. You’ll also have the XM subscription, which starts at about $40/month.

FAA Weather
Part of the ADS-B system that lies at the heart of NextGen is broadcast weather and other flight information (such as NOTAMs). As of this writing, we think the best supported ADS-B weather on the iPad is in WingX, which uses the SkyRadar ADS-B receiver from Radenna LLC. We’ve spoken to other vendors, such as ForeFlight, who plan to offer ADS-B support this year.

SkyRadar is a one-box solution with two fixed antennas for WiFi and ADS-B reception of flight information, as we’ll as a wired GPS receiver and power supply. The box can be stashed in the back like the XM units, however, the small ADS-B receiver might not be able to pick up a signal from the broadcasting ground stations if it’s too buried. We found in our testing that the SkyRadar box didn’t need to be in a window to receive, but it couldn’t be more than a couple feet from one. There’s an optional remote antenna for ADS-B you can hang in a better (inside the aircraft) location.

Reception is a weak point for ADS-B versus XM. XM is usually fully downloaded from the satellites by the time you’re done with a runup. ADS-B is broadcast from the ground and isn’t available for much of the U.S. until 1800 feet AGL or so. In the mountain west, it can be more like 10,000 feet AGL.

Like XM on ForeFlight, the ADS-B information on WingX is woven right into the airport and map just like weather downloaded from the internet, but they implement a bit differently. METARs, TAFs, NOTAMs and PIREPSs, as we’ll as forecast winds and temperatures aloft, appear in the airport information for specific airports. It’ll take you a couple taps to drill down to it. However, you can get color-coded METAR circles on any moving map.

AIRMETs, SIGMETs, TFRs and NEXRAD get overlaid on moving maps. If NEXRAD isn’t available, the chart will appear washed out so you can still use the chart while waiting for the image to download. Because ADS-B is a service of the FAA, it’s only available in the U.S. However, it is available in parts of Alaska where XM is not. 

Also because it’s an FAA service, there are no perks like the Current Icing Potential. Given the FAA’s budget woes, it’s unlikely these will be added any time before GA includes flying saucers. AIM 7-1-11 (d) lists all the information available, as we’ll as the coverage radii. Unlike XM, which broadcasts all weather for the U.S. and Canada to all aircraft, ADS-B broadcasts in for a range around each ground stations, so NOTAMs and TFRs may only show within 100 miles of your aircraft, only to later pop up as you get in range of another ground station. NEXRAD is broadcast at low-res for the CONUS and high-res for the local 250 miles.

One nice plus of the SkyRadar system is that it allows up to four WiFi connections and will stream ADS-B to all of them. It also passes on GPS position to the iPad.

SkyRadar’s ADS-B receiver is $950. A remote antenna is an extra $50. This is cheaper than XM to start and the weather is subscription free. SkyRadar also has some traffic information solutions in the works. FreeFlight systems has an installed system in development that will both meet the ADS-B equipage mandate (for $5000-$7000) but will offer a $75 add-on to transmit both weather and traffic to a portable like the iPad. 

Buying In
If you’re only in one aircraft and your flying profile needs things only XM can deliver—Canadian weather, data in the mountains, detailed icing information—then we wouldn’t hesitate to give a thumbs up to the Mobile Link system.

But for the wide part of the curve looking for the most economical way to get datalink weather onto an iPad, we think ADS-B is the way to go. The limitations seem a fair trade for subscription-free payoff. Not to mention the more of us who use it, the less likely some bureaucrat is to pull the plug to try and save a few bucks.

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