Stratus, the wireless weather receiver made for ForeFlight, has received a lot of attention since it was launched at Sun ‘n Fun in March. The promise of free in-flight weather on the iPad is exciting, but like any new technology it raises some questions as well. A lot of pilots are looking for a real world PIREP on the device to see how it really works in the cockpit.
We’ve been flying with Stratus for months now, and can share some helpful tips.
Reception is better than advertised
One of the main differences between Stratus and XM Weather is that Stratus uses the FAA’s network of ground-based ADS-B towers to receive weather information. The good news is that means Stratus requires no monthly subscription for weather. The bad news is that means your airplane needs to be at altitude to receive current weather, which can be a limitation compared to satellite weather. Also, some parts of the country do not yet have ADS-B coverage, so pilots should check the coverage map (at right) to see where any blank spots may be.
But while ADS-B coverage is certainly something to keep in mind, in our experience it’s not a major limitation. Coverage east of the Mississippi, through Texas and up the West Coast is generally excellent. In fact, the coverage map is conservative, and many pilots will get better performance than expected. At Sporty’s, we are 30 miles from the nearest ADS-B tower, but we receive data at just 300 ft. AGL.
Altitude helps too. ADS-B works a lot like the VOR system, so the higher you go the more stations you’ll likely receive. In cruise, it’s not unusual to get reception from 7 or 8 towers (but remember, 1 is enough). Also remember that the ADS-B system is rapidly being built out, so areas with marginal coverage are quickly being filled in. The optional external antenna will help if you live in an area of marginal coverage.
In the end, Stratus using a ground-based system to receive data has not been an issue for us. If you do most of your flying in Wyoming or Utah, an ADS-B system probably isn’t right for you just yet. But in most other locations, you can depend on reliable reception.
Don’t worry about high, medium and low towers
Just like the VOR system, there are different ADS-B station types that transmit different data. For example, low-altitude stations do not transmit national radar, only regional (full details here). In addition, there is no way to determine in the cockpit which type of station you are receiving–the system simply reports station location and signal quality. This could conceivably be an issue, since you wouldn’t know what data to expect along your flight.
In practice, though, this rarely matters. With over 50 flights under our belt, we have yet to have a flight where we didn’t have national radar. That’s not a guarantee, simply our experience flying with Stratus in the real world. There’s a good reason for this result: the ADS-B ground station network is laid out in a honeycomb pattern, with high stations surrounded by low stations and medium stations in a regular array. This increases your chances of receiving a medium or high station, which are the types that transmit national radar and long range text weather.
But even in the rare cases when you may not receive a medium or high station, you will still have a higher resolution regional radar picture updated every 5 minutes and complete METARs, TAFs, TFRs and NOTAMs within 250nm. This is certainly enough for most GA airplanes–and again, it’s a worst case scenario.
Radar resolution–XM vs. regional vs. national
Another key difference between ADS-B weather and XM Weather is the resolution of the radar display. Due to bandwith limitations, the ADS-B radar is not as high a resolution. Specifically, national ADS-B radar is much blockier than XM. But regional ADS-B radar is much closer to the resolution of XM.
While we’d all love to have high resolution radar everywhere, the split between lower resolution national and higher resolution regional radar on ADS-B works quite well. Regional radar is usually shown within 250nm of your airplane, which is over an hour of flying for most GA airplanes. This is excellent for detailed avoidance, especially close to your destination. Farther out, the national radar is still very helpful for strategic planning. No datalink radar should ever be used for penetrating storms, so the end result is the same with both systems–radar is a valuable source of information that should supplement what you see with your eyes.
Three pictures tell the story:
Mostly the same weather info as XM
ADS-B and XM transmit the same basic information, including: radar, METARs, TAFs, TFRs, SIGMETs, AIRMETs and Pilot Reports. These are certainly the critical elements to weather flying, and what most pilots buy an in-flight weather system for in the first place. But there are a couple of minor differences. ADS-B does not receive satellite imagery or echo tops, which are both options with XM. We’d categorize this as “nice to have” information more than “must have.” In particular, satellite is only updated hourly (or possibly on the half hour), so it’s much more of a pre-flight briefing tool than an in-cockpit weather avoidance tool. Also, ADS-B does not transmit lightning data like XM. But remember that this lightning data was not developed for pilots, so it reports only ground lightning. In our experience, this is of limited value.
But ADS-B does transmit some information that XM does not. NOTAMs is a great addition, for example. You can get updated airport information in flight with Stratus by tapping the Airports tab in ForeFlight, then the NOTAMs button. ADS-B also transmits special use airspace (SUA) information, including effective times, altitudes and frequencies.
Where to mount it
Since Stratus is totally wire-free, with an internal battery and no external antennas, pilots can place Stratus almost anywhere in the cockpit. The perfect location will balance three factors:
- Stratus looks down to the ground for ADS-B data.
- Stratus looks up to the satellites for GPS.
- Stratus can overheat if left in direct sun for extended periods.
Every airplane is different, so the best advice is to try many different locations in the airplane you fly to find one that works best. For example, many Cirrus pilots have success with Stratus in the glove box on the right side of the panel. Because the airplane is composite, Stratus still gets excellent reception in this location. An all-metal airplane like a Cessna or a Piper may need a more direct view, like the glare shield. If this gets too hot for Stratus (see next tip), other options include the co-pilot’s seat, a back seat, the baggage compartment or even the floor (ADS-B reception is often good here, believe it or not). You can easily see whether a location will work using the Stratus Status page in ForeFlight Mobile. This page shows the number of ADS-B stations being received as well as the GPS signal quality at the bottom. Move the box around and see what these two indicators say.
What about jets or airplanes with a heated windshield? We’ve flown Stratus in numerous high altitude airplanes, and the altitude itself does not have an effect. However, the heated windshields found on most turboprops and jets will degrade performance on both the GPS and the ADS-B receiver. In many cases, Stratus is still completely usable–we’ve seen GPS accuracy, for example, go from 1m to 6m when under a heated windshield. This is still extremely accurate, so the slightly worse performance has no impact on flying.
If the heated windshield does seem to be causing serious interference with Stratus, try a side window, which is often not heated. If your airplane has a DV window (the little triangle window on the pilot’s side), this can be an excellent place for Stratus, since it has a clear view of both the ground and the sky and the window is not heated. The optional suction cup mount is another excellent option, as it improves reception and virtually eliminates overheating.
We’ve flown Stratus in a wide variety of airplanes: Citabria, Cessna 162/172/182, Piper Warrior, Mooney, Piper Aztec, Pilatus, Citation and Lear 60 to name a few. We haven’t found an airplane yet where Stratus simply won’t work–it just takes some experimentation.
Be aware of possible overheating
Just like the iPad, Stratus includes a large lithium ion battery which can overheat if exposed to extreme temperatures. To protect itself, Stratus will shut itself down before it gets too hot and show the pilot an “Stratus HOT” message in ForeFlight. To prevent this from happening, it’s a good idea to avoid direct sunlight for long periods of time. Half an hour on the dash will not cause Stratus to overheat, but if you’re flying two hours directly into the sun, it’s a good idea to put Stratus in a different location. This has not been a regular issue in our flight testing, but it can occur; it’s just something to be aware of. In general, you should treat Stratus like you treat your iPad–for example, don’t leave it in the airplane if you tie down outside.
Touch screen makes a difference
Some weather data is simply easier to see on an iPad. It may sound obvious, but we’ve flown numerous trips in airplanes with both panel-mounted weather and Stratus. In most cases, we ended up using the iPad to view weather. It’s simply easier to tap on a SIGMET and read the pop-up box than it is to scroll around on a panel-mounted MFD. PIREPs are also great on the iPad, not to mention the ability to do “rubber band” flight planning around weather systems, right in ForeFlight.
Overall, Stratus simply works. After an initial flight or two to find the right location and to get comfortable with it, Stratus stays out of the way and reliably delivers GPS and weather data. There’s no setup or tricks to learn–just turn it on and go flying.
For more information on Stratus, visit sportys.com/stratus.
Watch our 6-minute video on “Getting started with Stratus” below: