Fly a few trips with one of the new datalink weather setups and you'll be spoiled for life. My experience has been with the Honeywell Bendix/King system installed in the AOPA Air Safety Foundation's online auction airplane — an EADS Socata TB 20 Trinidad dubbed the Spirit of Liberty (see " Sceni-cruiser," June Pilot). My most recent flight in the airplane provided an especially good demonstration of datalinked weather's value.
The flight was from the Frederick Municipal Airport in Frederick, Maryland — AOPA's home airport — to Oxford, Maine. For the most part, this would be a flight on instruments.
Here's the synopsis for that mid-June morning: A weak surface low over central Pennsylvania had a cold front extending to the south and east, and a stationary front extending to the west. The cold front had a southward bulge to it, aligned so that it passed right over Frederick. North of this front, a high-pressure center was anchored over Massachusetts.
The clockwise flow around the New England high was causing trouble by creating radiation fog and low ceilings. North of the cold front, evening temperatures dropped to the 50s and 60s. Those temperatures, plus the airflow from the Atlantic, kept most of New England under a blanket of clammy clouds.
For the early morning departure, Frederick had a 700-foot ceiling with two-mile visibility. About 40 nm to the west a large cluster of thunderstorms packed with Level 5 radar returns was creeping toward Frederick. These were ahead of the stationary front. Flight service was predicting that they'd move across the rest of Maryland by midday and linger until well into the night — long enough to affect my return trip.
Oxford, which has no weather-reporting capability (I used nearby Auburn-Lewiston's airport observations), had 500 feet overcast and one-and-a-half-mile visibility in mist. The ceiling was forecast to lift to 1,500 broken by late morning, and the mist was supposed to burn off, too, and leave me with unrestricted visibility for the arrival. It sounded like your typical morning burn-off situation, but that cloud cover, those cold temperatures, and all that Atlantic air made me wonder if the mist wouldn't burn off later rather than sooner. After all, daytime high temperatures in Maine were forecast to hit a mere 64 degrees Fahrenheit — only 10 degrees higher than the temperatures at dawn.
Of course, I received a standard preflight weather briefing before leaving the house; datalink weather won't change that ritual. But once in the air, I was working that multifunction display (Bendix/King's KMD 550) for all it was worth.
First, I was interested in the thunderstorms to the west. By calling up the radar view I could confirm that, yes, the storm cells were indeed at Frederick's doorstep. By the time I was over New Jersey, a huge cell was over Frederick. The Stormscope view confirmed this by plotting a big blotch of activity in that area.
I also needed to see how things were holding up near Oxford. Another push on the 550's WX button brought up the METARs page. In this mode you can use the 550's joystick to make the display show METARs for:
- Stations along the flight-planned route entered into the airplane's GPS receiver,
- Six reporting stations near the departure and destination airports,
- The six nearest airports at the time you make your request, and
- Six user-defined airports with weather-reporting capability.
TAFs (terminal aerodrome forecasts) and pireps can be displayed the same way. The display will also tell you how old each report is — in minutes.
This feature let me check on Auburn-Lewiston's weather as I flew. Every so often I'd call up the weather for various airports — using the 550's joystick to select the airport identifier — and monitor the goings-on. Sure enough, the ceiling wasn't lifting to any 1,500 feet. However, in the home stretch I saw that conditions suddenly went to 1,000 broken and five miles visibility. This meant that I could shoot the GPS approach to Oxford and be reasonably certain I'd be able to descend below the ceiling and make a legal landing.
Big deal, you might say. You can always call flight watch (122.0 MHz) and obtain the latest METARs and other weather information. True, but how many times have you contacted flight watch, made a request, then stood by helplessly while someone else's radio transmission stepped all over some critical bit of information the specialist was trying to tell you? Now that's frustrating, but you don't have to deal with it — if you have uplinked weather.
Datalink weather in the cockpit also means you don't have the workload associated with tuning in any AWOS or ASOS broadcasts as you fly en route — something I always do to know the
surface weather I'm overflying.
However, datalink isn't without complications. For one thing, most datalinked weather information is encoded, so you have to be savvy enough to translate reports so you can understand them. Also, datalink leaves more of the decision making to you. Rely on it alone and you won't have the benefit of a trained briefer or flight watch specialist to help you identify courses of action when the going gets tough. You also won't have them to identify the boundaries of a convective sigmet — which datalink has yet to bring into the cockpit.
Reception is another issue. For example, the Honeywell Bendix/King system uses a network of ground-based transmission towers. This means line-of-sight restrictions. For good reception you have to be flying anywhere from 5,000 to 10,000 feet agl in many places in the United States. With systems that use satellites to broadcast datalink weather this isn't a problem — from space, satellite signals have a clear shot at any airplane, whether it is on the ground or in the air.
Then there's the workload associated with operating the black boxes that provide the datalinked weather in the first place. When the heat's on and it's dark, turbulent, and scary, you've got to know how to work your equipment — and know when to ignore it and go back to basic aviating.
Currently, several manufacturers offer datalinked weather services. This article is not about comparison pricing, but you can expect to pay about $3,000 to $4,000 for a datalink receiver, plus a monthly access fee, plus a couple thousand dollars more for a compatible display unit — if you don't already have one associated with your GPS receiver.
No doubt about it, stepping up to datalink means taking on another expense. But it's well worth it, in my opinion. In a few years I'll bet that datalinked weather in the cockpit will be a standard feature in more and more general aviation airplanes. Once full packages of weather information (e.g., convective sigmets, airmets, radar reports, and satellite imagery) are available the competitive pressure will really be on. From there, it's a short step to datalinked air traffic control clearances.
Here's another caveat: Datalink weather can give you plenty of raw data, but it won't prevent you from making bad judgment calls. All the money and information in the world can't help an unprepared pilot if he decides to press on into adverse weather. Invent a machine to fix that, and you'd win the Collier Trophy.
On the return trip, I flew a nondatalink-equipped airplane. Of course, the storm cells were parked over Maryland. And yes, when I called flight watch to learn about the cells' locations someone stepped all over the briefer's response, so I had to ask again — and again. Then ATC announced a new convective sigmet, and it was over to a HIWAS frequency to get the details. I yearned for that Trinidad's datalinked display of ground-based weather radar imagery. It would tell me where the heaviest precipitation returns were located.
With ATC's help I steered clear of the worst weather and shot the ILS to Frederick in a 600-foot overcast. All's well that ends well, but I somehow felt naked without datalink. I realized that I lacked vital elements of situational awareness. You can't put a price on that.
E-mail the author at [email protected].
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