Tuesday, May 22, 2012
ADS-B Weather In The Cockpit
Sporty’s Stratus with ForeFlight 4.5 for iPad
Sporty's Stratus is a whole new ballgame—assuming you already have an iPad (which I do). Just $799 gets you not only NEXRAD imagery (in color) and a variety of text weather and safety products, but also an external GPS with Wide Area Augmentation System (WAAS) support that delivers one-meter accuracy. Best of all, there's no need for a weather subscription—buy the unit, set up ForeFlight Mobile (an iPad app) to connect with it, and all the weather you download is absolutely free.
Unlike satellite-based systems, Stratus relies on signals from ground stations of the FAA's autonomous dependent surveillance-broadcast (ADS-B) network. Specifically, Stratus receives flight information service-broadcast (FIS-B) data, and then relays it to the iPad using a wireless Ethernet link. ForeFlight Mobile then takes that data and puts it on the display. FIS-B data available for display through Stratus includes NEXRAD weather radar for the entire U.S., AIRMETs, SIGMETs, METARs, TAFs, NOTAMs, pilot reports, special-use airspace and winds/temperatures aloft.
Before trying Stratus, I was concerned about how much altitude you'd need to receive signals (earlier ground-based data-link weather systems required several thousand feet of altitude for good coverage). I needn't have worried—when I looked down at the iPad strapped to my knee during climbout on a brief test flight on a rainy day near my home airport (Modesto, Calif.), it showed a band of rain that had just passed over the field. It worked equally well throughout a 518 nm round-trip between Modesto and Hawthorne, Calif.—including flight over the Tehachapi Mountains. Based on this experience, I expect it to work well wherever ADS-B coverage is available.
Aside from the Stratus unit, which measures 5.8x4.2x1.1 inches, weighs eight ounces and sits on your glare shield, you'll need an iPad (while the original version works, version 2 or higher is recommended) and the ForeFlight Mobile app, version 4.5 or higher. Downloading the app is free, but using it requires a subscription for charts and airport data.
ForeFlight displays NEXRAD data, field conditions and TFRs graphically; to get text data, you tap on the colored icon for an airport and look at the resulting pop-up menu, or switch from the map to the airports tab and look up weather or NOTAM (including TFR) data there. (NOTAMS not associated with a particular airport can be called up from ForeFlight's Device tab). If you already know how ForeFlight works, Stratus makes the ADS/B data available in a very natural way. If you're new to ForeFlight, it won't take long to learn.
Stratus isn't perfect—it's supplied with a 110-volt charger, which is used to charge an internal battery that's supposed to provide eight hours of continuous operation. On the longer of my two test flights, I found that the unit went from a 100% charge down to 30% after 4.6 hours. Sporty's sells a cigarette-lighter adapter so you can power the unit in-flight, and I'd recommend that to anyone planning to fly really long legs. Documentation is sparse: Stratus comes with a 15-page quick-start guide that tells you how to set it up, but refers you to ForeFlight for details on how the data is displayed; but I was able to figure it out very quickly. And because it receives FIS-B data, it's limited to what the FAA provides—you won't get high-end weather features like echo tops, lightning or animated forecast graphics. That said, for in-flight weather without a subscription, it's the best deal I've ever seen. I wholeheartedly recommend it!
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