XM Weather on the iPad

XM Weather on the iPad by Peter Cassidy
AirPlay First Quarter 2012

In October 2011 ForeFlight added support for XM satellite weather overlaying radar, METARs and other XM weather products on the ForeFlight maps on your iPad. It’s a major enhancement that makes the iPad an even more useful device in the cockpit. Here’s a look at what’s involved and how well it works.

Adding XM Weather to the iPad
On the hardware side, you need an XM weather receiver and the WxWorx Mobiile Link box. The current weather receiver model is the third generation and sells for about $1000 depending on the options. Older models will work just fine. The weather antenna is a small puck-like unit that I Velcroed to my glareshield after removing the magnet.  Weather data from the receiver is sent via USB cable to the Mobile Link box which sends it on to the iPad using Wi-Fi. To view the weather you need an application like ForeFlight that supports XM weather. You also need a subscription to XM weather service which costs $35-$100/month depending on the options. Be aware that, at this time, ForeFlight does not support all the weather products XM offers.

The WxWorx receiver uses either 12 or 28 VDC power. The latest generation receiver can also be powered via the USB cable from Mobile Link which is very convenient. Mobile Link, however, only works on 12VDC. If you need it, WxWorx sells a 12 to 28 VDC converter for $19.

The Mobile Link box is reasonably compact measuring approximately 6”x4”x1”. It has a 6” antenna like your wireless router at home. In my aircraft, the Wx receiver, Mobile Link, and a 28 VDC to 120 VAC converter sit on the floor behind the pilot seat and automatically powers up when I turn on the battery master switch. The Wi-Fi signal is strong and the weather receiver antenna cable is long so these units could be located almost anywhere in the aircraft.

The latest WxWorx receiver includes a built in GPS. However, it is not supported by ForeFlight so your iPad either needs to be the 3G model with the built-in GPS or you need to purchase an external one.  I’ve had good luck with the iPad’s internal GPS and have no plans to add an external one. Unlike browsing charts, a reliable GPS is important when working with weather. The internal iPad GPS has not always started reliably in the air. When I first started using my iPad it was either slow to start or occasionally would not start at all. Recently this has not been an issue. I suspect software changes by Apple are the reason for the improved performance.

Since my iPhone also has ForeFlight installed, it can it can also be used to view XM weather. However, only one device can access the weather at a time. If you have two iPads in the cockpit only one can be displaying XM weather.

PIREP XM on the iPad
I’ve been flying with XM weather on a tablet PC since 2005 and believe it's a good investment if you do any amount of cross country flying. I have resisted the temptation to add weather to my Garmin 530 navigator, partly due to the cost, but mostly because I like the flexibility of having it on a tablet.

I have the Aviator level of XM service which gives me lightning and Canada coverage. I use an iPad for all my charts and no longer carry paper charts except for Canada backup. Adding XM to my iPad enabled me to retire my HP Slate 500 tablet PC. Now, one tablet does both weather and charts in the cockpit. I did lose some functionality giving up my HP tablet, but none of it is critical except for lightning. I understand ForeFlight will add lightning before long, otherwise I would probably drop my XM service back to Basic level and save $20/month.

While XM worked well on my HP tablet, it’s even better on the iPad. The display is more readable on the iPad. I keep the display intensity at the brightest setting which shortens the battery life a small amount. This is not a problem because I put the iPad in standby when I don’t need it. The other major benefit of the iPad is the display is significantly larger then my HP tablet and most EFBs which makes it better for viewing charts and weather.

Starting up XM weather on the iPad requires no action, it's automatic. The XM receiver and Mobile Link boxer start up when I turn on the battery switch. The iPad automatically connects to the Wi-Fi network and XM weather starts showing up on ForeFlight maps within about 5 minutes. This simplification in startup over my previous setup is important as it happens when you need to be concentrating on other pre-flight activities. I was surprised at how much I appreciated this improvement.

The weather interface on the iPad is the same as when you’re connected to the ForeFlight servers via the Internet. You know it’s XM weather you’re getting by an XM WX time stamp at the top of the screen. This time stamp  also tells you how old the radar data is.

XM weather overlays on your flight plan route and the GPS shows your current position. ForeFlight has added a new map called World Map. It's a basic map that is ideal for studying weather. Switching between map views is easy and the weather stays on top of all of them. Also new in version 4.2 is the ability to set the transparency of the weather overlay. This is important when you have a large area of weather and are trying to understand the places it covers.

XM weather data is buffered in Mobile Link so that if you put your iPad in sleep mode or change to another application, the downloaded weather data is not lost. It takes about a minute for the iPad to resync the weather. This means you don’t have to have your iPad on for the entire flight to collect weather data, something I had to do with my HP tablet.

There is a page where you can check the signal status of your XM receiver. This is useful if you find radar updates are slow which could be due to satellite signal problems. I’ve had this from time to time over the years and it’s something I pay close attention to when I'm close to significant weather. I would like to see ForeFlight provide a small graphic of signal quality on the map page.

A feature ForeFlight does not have that I miss is range rings around your current aircraft position. I like to have a 25 mile ring to gauge my distance from significant weather. Another wish-list item is a current track line that projects about 50nm ahead of the aircraft as a guide in maneuvering around weather.

Alternatives to XM on the iPad
The iPad/ForeFlight/Xm package is just one of many electronic flight bag solutions that include XM weather. Deciding which alternative is right requires some study. Each has their strengths and limitations. Buyers need to look closely at the various capabilities and compare them with their specific needs.

From a weather perspective, the advantage of the Garmin 364-796 series of units is that everything is integrated into one box. If you frequently move your setup between airplanes, this is the only way to go. Multiple boxes with the iPad are not a problem if it is always left in the aircraft. Cost-wise the two solutions are very close when you include the cost of the iPad. I looked hard at the new Garmin 796. However, since I have a Garmin 530 moving map navigator in my panel, I don’t need the navigation capabilities of the 796. Also, I much prefer the larger iPad display.

A recent alternative worth serious consideration is the free weather provided as part of ADS-B. For this you need the SkyRadar receiver which costs about $1200 as well as an application on the iPad that supports it. Wing-X supports SkyRadar, ForeFlight does not. While the hardware cost in about the same as XM on the iPad, the weather service is free, which is a substantial saving. At this time, ADS-B coverage is limited. However, by 2013 the entire country should be covered and this will no longer be an issue. Another plus for FIS-B is it provides traffic advisories. While this is a new service with some limitations, there is no doubt is will work well for many users.

Overall, the iPad wins when it comes to the large display. However, a large display is a mixed benefit. Larger is good for reading charts and weather, while smaller is better for yoke or panel mounting. I have no plans to yoke mount my iPad. It mainly sits on my lap and that location works well for me. I do have a 6”x6”x1/4" clear polycarbonate yoke mounted table that the iPad often sits on during cruise flight. It’s held in place by a simple clip from a kitchen store. Despite its size, the iPad does not block the view of flight instruments. Velcro strips would secure the iPad to my yoke mounted table, realistically though, I consider the iPad is too large. A smaller form factor like the Garmin 796 is what's needed. In any case, this simple setup is handy and works well except in turbulence or during takeoff and landing. The clear polycarbonate allows the clock to be visible when the iPad is not there. There is speculation that Apple will develop a mini iPad with a screen about the size of the Garmin 796 that could be yoke mounted.

XM weather on the iPad is an outstanding addition and ForeFlight have done a great job integrating weather and charts. The iPad and similar devices are powerful tools in the cockpit that seriously challenge the alternative of FAA approved equipment. I have long resisted adding XM weather to my Garmin 530, partly due to the significant extra cost, but more so because I prefer the flexibility of having the weather on a separate screen. Weather is just one of many capabilities that work very well on portable devices. Traffic, terrain and obstacle avoidance, synthetic vision are also available.