On Display

Packing a satellite-weather punch

The late-spring nor'easter was still draping scud with its western arm, which spiraled across the route we plotted from Frederick, Maryland, to upstate New York. Perfect weather for a flight in which we'd test Avidyne's FlightMax EX500 multifunction display (MFD) with its latest goody — datalink weather via XM Satellite Radio.

The EX500 has a 5.4-inch-diagonal screen; the unit measures about 4.35 inches high by 6.25 inches wide, making for a reasonable fit in many panels. Keeping in line with previous FlightMax MFDs, the EX500 accepts a long list of radar interfaces, as well as a hefty handful of traffic, terrain, lightning, and GPS inputs. Avidyne's CMax instrument and airport charts also can be displayed on the EX500.

And Avidyne has offered datalink weather almost from the EX500's debut via its modified request-reply system using Orbcomm satellites. While request-reply systems used by other datalink weather providers require the pilot to actively request a message from or send a message to the provider's hub for each weather update, Avidyne developed a process it calls Narrowcast, which automatically requests weather information according to the aircraft's current route and parameters set by the pilot. This system remains available to Avidyne customers. Since the subscriber pays only for the data requested, the system makes sense for pilots who fly cross- country infrequently — perhaps only a few hours each month or during the more flyable seasons each year.

But for pilots who navigate the weather on a regular basis, Avidyne has partnered with XM Satellite Radio to provide broadcast weather to the EX500. XM's datalink weather products are developed and packaged by Wx Worx, based in Melbourne, Florida. While both Narrowcast and XM weather services deliver Nexrad radar graphics, METARs, airmets and sigmets, and temporary flight restrictions (TFRs), the XM broadcast system updates weather at a faster rate than is available through Narrowcast. Pilots receive ground-based lightning information through the XM system as well, depending on the service plan that they choose.

Narrowcast does hold one advantage: text messaging. The system automatically sends position reports to Avidyne's Network Operations Center (NOC, pronounced "knock") to provide flight tracking for family, friends, and business associates to whom the pilot has given a password and N number for access to the Web site ( www.myavidyne.com). Upon landing (once the groundspeed falls below a certain threshold) the EX500 automatically sends an "end of flight" message to the NOC. Those on board the airplane can also send text messages through the NOC to those who can access their page on the site.

So there's reason for subscribers to want both the Narrowcast and the broadcast XM systems, and Avidyne has answered with MultiLink, a subscription that supplies both.

Looking for weather

Fred Scott, AOPA 295113, has flown his 1980 Beechcraft B55 Baron, our test platform on our flight to New York, from his grass strip near Charlottesville, Virginia, to Canada and the Florida Keys. He's a big fan of datalink weather and "how really useful this information can be in preventing flight into terrible weather." (See " Wx Watch: Radar Revolution," page 167.)

In fact, Scott likes all kinds of radar and has a Bendix/King RDR 160 analog radar unit with a 12-inch antenna in the nose of his Baron. While he's used the on-board radar a lot over the years, if datalinked Nexrad had been available, he probably wouldn't have installed the on-board unit because of Nexrad's greater utility in light aircraft. Aviation safety pundits have opined that Nexrad weather is useful for strategic weather avoidance, while airborne radar remains the best option for tactical dodging. These basic rules of thumb certainly apply, but there are caveats to both.

Some Nexrad graphics are composed from base-reflective images delivered from ground-based radar sites around the country. They give a good view of the heaviest areas of precipitation within a given storm — but only up to a certain level. Wx Worx constructs its storm graphics from composites of several radars that paint different altitudes of a storm's precipitation levels. The radar that senses the highest decibel strength in a given 2-by-2-km column of the storm is used for that column — for example, if the highest strength was at 14,000 feet and would be depicted with a red pixel, that red pixel is what would display within the image. Or if activity near the top of a particular storm column, at, say, 35,000 feet is strongest, that color pixel will be displayed for the column.

On-board weather radar is a head-on view, however, and therein lies both an advantage — you see the strength of the storm at your general altitude — and one of its limitations. Depending on the strength of the radar and the diameter of the antenna on board, only so much energy is transmitted from a given unit. Greatly simplified, attenuation results when the radar energy is absorbed or scattered by suspended water near the "front" of the storm, as viewed by the pilot, masking potentially heavier activity behind it.

The two sources of information, radar and Nexrad, provide great tools for a pilot trying to stay a good distance from convection — as long as that pilot keeps well in mind that what lurks behind and above these images could be worse than what shows up on the screen. Lightning strike and cell depictions fill out the picture — on the EX500, through datalink from the ground-based National Lightning Detection Network or input from an on-board L-3 WX-500 Stormscope. The EX500 displays strikes that are color coded to show their relative age, changing from yellow to gray over the course of 11 minutes.

During our test flight, we aimed for a large-scale, yet slowly dying storm that had parked off the coast of New Jersey. Of course, we had no intention of getting near the core of the weather. Though ceilings were relatively high at Frederick, we were in the clouds at 3,000 feet and found few layers as we headed northeast at 5,000 feet.

We compared the radar image to the Nexrad images downloaded via XM; you cannot display both at once — the EX500 can overlay either radar or Nexrad. When radar is displayed, soft keys on the EX500 allow you to cycle through Standby, Test, On, and Off, making a separate radar control panel unnecessary.

The Nexrad graphics allowed us to look farther afield than the radar, which only started picking up the outer reaches of the storm from 80 miles out. With Nexrad images from the entire continental United States available within a few minutes of engine start, we could see exactly where the storm was before we even took off. A special dispensation from Potomac Approach allowed us to blow past a waypoint so that we could come closer to the storm; only then did we see evidence on the radar display about the dangers that lay in a course straight ahead.

Scott has archived several pairs of digital photos he's taken on past flights showing similar contrasts between what he's seen on Nexrad, and how it blossoms on radar later — or not, depending on the contours of the weather.

Graphical METARs overlay on the moving-map display as well, giving a sense of the conditions at airports along the route. The icons resemble windsocks, and they are color-coded blue for good VFR, green for marginal VFR, yellow for IFR, red for low IFR, and magenta for less than Category I ILS conditions. With the Narrowcast function (either alone or as part of a Multi-Link package) pilots can acquire data outside the continental United States into Canada and the Caribbean. On the Trip page, a list of waypoints along the route also shows weather nearest to that waypoint, with an icon next to the identifier, and text weather displayed at the bottom of the screen when the cursor highlights that waypoint.

With its most recent software update, Avidyne has added the Airports Nearest to Destination page to the EX500, accessed with the Nearest key. Pushing this button calls up the nearest airports, VORs, NDBs, and intersections as well. The Airports Nearest to Destination page lists airports within 100 nm of destination for easy diverting and lists each with a METAR icon; the decoded METAR is shown at the bottom of the screen for a selected airport, and a chart icon next to the airport identifier indicates whether the airport has an instrument approach available — a dedicated icon shows if the approach is an ILS — so you can quickly determine whether you can get in.

On the chart

CMax on the EX500 provides access to Jeppesen's JeppView electronic instrument approach charts and airport diagrams through a dedicated Chart page. The Auto Fill function selects all destination airport charts, or any chart in the worldwide database can be accessed for any other airport. The View button cycles through header, profile, minimums (known as datafields in EX500 parlance), and plan views; the active leg on the chart turns from green to magenta as you join the leg, making for instant situational awareness on the procedure. CMax automatically cycles from the approach chart to the airport chart for the destination and your aircraft icon shows up on the airport diagram once your groundspeed goes below 50 knots.

For pilots accustomed to flying with Jepp charts, using CMax should feel seamless. Jeppesen sends out an update to CMax charts every two weeks; if the pilot hasn't updated the charts in the past 10 weeks, CMax won't display.

Other goodies

When we returned to Frederick, the traffic inputs to the EX500 took on more importance — though we had a couple of call outs while in the clouds. A light- blue icon displays until the target's proximity dictates a change to yellow or red. Relative altitude in hundreds of feet is displayed beneath the icon. Traffic interfaces include Honeywell TCAS (traffic alert collision avoidance system), L-3 Skywatch systems, Ryan TCAD and 9900BX traffic advisory systems, and Garmin's GTX 330 transponder with TIS (traffic information system).

Terrain is depicted on the base map with several levels of declutter. A full topo map cycles to a standard base map (water shows in blue) or no base map (all black) when the pilot presses the Declutter soft key. In general, soft keys displayed on the screen also time out after a user-defined period of time to declutter the display. An Americas terrain and obstacle database provides positional awareness information; the EX500 also accepts input from the Honeywell EGPWS (enhanced ground proximity warning system). An international terrain database is available separately.

Price: $8,995 for basic unit, additional cost for radar interfaces and XM datalink receiver; add CMax for $2,495; XM datalink service pricing includes a $75 initialization fee and $29.95 or $49.99 monthly charge; Narrowcast datalink pricing includes a $99 registration fee and data costs either 9 cents per message unit or $600 annually for unlimited messages.

Contact: 800/284-3963 (AVIDYNE); www.avidyne.com

E-mail the author at [email protected].

Links to additional information about Avidyne products and datalink weather may be found on AOPA Online ( www.aopa.org/pilot/links.shtml).