by Lionel Lavenue
As you trod forlornly against the headwind from hell, have you ever wanted to know exactly what direction its coming from and how it changes with altitude? Ever wanted to give Flight Watch the exact wind information during a pilot report without fussing with the unknown wind page on a GPS? If so, then youve probably thought about buying an air data computer.
These are standard equipment in air-carrier aircraft and many bizjets and turboprops also carry them. As most owners learn early on, flying an airplane is a game a numbers and the higher the performance, the more the numbers really start to matter. And most performance numbers are built of a foundation of density altitude, something you calculate by knowing the temperature and the altitude. Having that data constantly available opens up some practical interaction with a GPS, where it can be used to calculate winds and do fuel computations.
When I purchased my new Cessna T206H, the first order of business was to pull the Bendix/King stack and install a Garmin stack. (Im hoping that Cessna will get with the program on this and offer both Bendix/King and Garmin gear as options).
While my airplane underwent major surgery, I figured it was a perfect opportunity to add an air data computer.
Obviously, air data computers are specialized gadgets so the market isnt exactly flooded with them. And they arent cheap, so not everyone considers them indispensable. For the light aircraft crowd, there are essentially only two companies plying the market: Shadin and Insight, maker of the GEM line of engine monitors.
What They Do
An air data computer automatically provides a pilot with information that normally requires an E6B and an OAT to calculate. This air information includes density altitude, pressure altitude, indicated airspeed (IAS), true airspeed (TAS) and total air temperature (TAT).
When connected to a GPS, this gives the box all it needs to calculate winds aloft. If theres a fuel totalizer aboard, data from the transducer can be fed into the various boxes to calculate fuel-required to waypoints and endurance.
An air data computer needs several inputs for the basic air functionalities: pitot pressure (for airspeed), static pressure (for altitude), altimeter baro setting and outside air temperature. For winds aloft, heading synchro is also needed. All of the air data computer products offer fuel totalizing and this capability requires the input of fuel flow from a fuel transducer.
Both Shadin and Insight provide all the hardware. You just need a good avionics shop and the appropriate navigators to display the information you want to see.
Shadin is well known for its line of fuel totalizers. In our estimation, the Miniflo series is found in more piston aircraft than any other brand.
Shadin makes three models of air data computers and is expected to shortly introduce yet another one. Currently, it markets AirDataComputer-200 (ADC-200), the ADC-2000 and the DigiData, a standalone panel mount unit. Not surprisingly, these air data computers have excellent fuel totalizing capabilities.
The ADC-200 is a remotely-mounted box that interfaces with your GPS. All input and output is conducted via the GPS. On start-up, the GPS asks for fuel information and baro setting and the ADC-200 tracks this information automatically in the background, allowing the data to be displayed on the GPS.
With a Garmin 430/530, the GPS software automatically displays certain air data information on the main screen (such as direction and speed of the winds aloft).
Most GPS software also provides other back-up screens dedicated to air data and fuel such as fuel used, fuel remaining and fuel endurance to destination.
The ADC-200 doesnt offer altitude alerting but Shadin offers a separate product for these features, the Shadin Altitude Management System.
The ADC-2000 is the same as the ADC-200, except it can automatically read the baro setting from the high-end digital altimeters and automatically feed the setting to other devices, such as a GPS.
The ADC-2000 has a ARINC-429 bus device, which allows it to act as an interface with high-end aviation equipment more likely to be found on airline and bizjet equipment than in a GA single-engine airplane. Also, the 2000 is more heavily shielded from vibration, and it is recommended for use in high vibration environments such as helicopters. The ADC-2000 is approximately $1500 more than the ADC-200.
As we go to press, Shadin is awaiting certification for its new AMS-4000. This unit will combine the ADC-200/2000 with Shadins Altitude Alert System. This combined package will serve as a direct competitor to the Insight TAS unit, which also has a display. Shadin is expecting certification soon but beyond that, we dont have any operational details about this device.
Were told that an upgrade will be available to current customers who already own the ADC-200.
The DigiData is a panel-mounted unit that combines the functionality of the ADC-200 with a standard panel-mounted Shadin fuel totalizer.
The advantage of the panel mount is that the pilot can include the displayed DigiData information in his or her scan and this instrument provides all the information you need in one easy-to-read format.
The disadvantage of the panel mount is that the DigiData is somewhat dated. The panel-mounted unit is itself quite antiquated looking, in our view, especially in contrast to the new modern MFD panels. Also, this device lacks features found in many top-of-the-line devices, such as auto-dimming.
Moreover, in our view, the DigiData has an involved operating logic that takes some learning to get used to. When youre topping tanks, the DigiData data doesnt offer a variety of storable full options to accommodate various fuel system options, such as aux or tip tanks.
It has one programmable full option and if youre fueling outside that fixed value, you have to add or subtract fuel manually, by the gallon. This requires an awkward double finger entry procedure of the sort most avionics manufacturers have designed out of their operating logic.
Further, if you are upgrading and adding air data, the remote box will be the better choice in the vast majority of circumstances, simply because modern navigators are equipped to handle air data inputs.
For these reasons, the DigiData isnt our top choice. Depending on your tastes and how unified you want your panel to look, it may look too dated to consider. This will be doubly true if youre installing an entire suite of new avionics, such as a full Garmin or UPSAT stack.
The newest entry in the air data computer market is the Insight TAS-1000, as previously reviewed in the June 2001 issue of Aviation Consumer. The TAS-1000 has all the features of the Shadin products and more. For example, the TAS-1000 includes a unique and patent-pending Windicator device, something thats not available with any of the Shadin products just yet.
The TAS-1000 is a small panel-mounted instrument with considerable computing horsepower. It looks like an altitude alerter, and in one sense, it is. The TAS-1000 is not simply an air-data computer that provides air and fuel information, but a multi-purpose computer that provides a wide range of information. The TAS-1000 furnishes all of the same information available from the Shadin products and it also provides altitude encoding, altitude alerting and other unique features.
The small TAS-1000 is easy to use. On start-up, the TAS-1000 queries the pilot for full fuel and this query includes three preset full amounts, such as standard-say, full without tip tanks-and extended, perhaps with tip tanks full. If you forget to enter full, the TAS-1000 remembers the fuel used since start-up, if you later choose full fuel.
Another unique feature of the TAS-1000 is the unique Windicator device. The Windicator is a separate panel-mounted device with a display about the size of a quarter that simultaneously displays wind speed, wind direction, crosswind component and wind correction angle.
We like the Windicator idea and the display itself, but for crowded panels, even the small Windicator could prove a challenge to install. Still, after we saw the TAS-1000 and Windicator, we were impressed with its capabilities.
Despite these advantages, Insight has not been able to market the TAS-1000 widely. We blame much of this on the fact that shops dont want to deal with Insights installation requirements, specifically the need to buy specialized equipment. (Read on.)
Both the Insight and Shadin units perform as advertised but there are definite differences between them. For example, as a newer unit, the TAS-1000 is of a better, more sophisticated design than the Shadin, in our view.
The Shadin products have numerous circuit boards, whereas the TAS-1000 has one. The Shadin products have pressure transducers wrapped in cotton and secured by a piece of tape, whereas the TAS-1000 is formed within a machined oven and molded into the products housing.
Prior to our installation, we knew that we wanted to connect our air data computer to a Garmin 430/530 stack. We called Garmin and asked for recommendations. The Garmin tech rep immediately recommended the ADC-200.
He explained that Garmin had an excellent working relationship with Shadin and noted that the 430/530 were specifically designed to work with the Shadin products. When we asked about the TAS-1000, the Garmin rep said he hadnt heard of the product.
As promised by Garmin, following the installation of the ADC-200 in our Turbo Stationair, the ADC-200 worked perfectly. The installation shop had no trouble installing it or configuring it to the 430/530 stack.
Excluding the DigiData-for the reasons noted above-the primary choice between the Shadin ADC-200 and the Insight TAS-1000 boils down to whether you want a panel-mounted unit or not. If not, the pick is the ADC-200. If so, then the pick is the TAS-1000.
Originally, we had picked the TAS-1000 as our top choice and we called our avionics shop to schedule an installation. We were shocked when we received a quote of $7000. We then called some other shops, but none would quote us for a TAS-1000. They all recommended the ADC-200.
Frustrated, we called Insight and we learned of a unique problem. To install a TAS-1000, Insight requires that dealers purchase a dealer kit that costs about $2000. The kit includes a test box and panel punch, which Insight insists results in a high quality installation.
For a small volume item like air data computers, we dont think that the dealer kit makes any sense and it clearly is hurting Insights sales, if our experience is typical.
After learning of this, we changed plans and asked our avionics shop for a quote on the ADC-200. We were pleased with a quote of no more than $3000, which included installation and interface with the Garmin equipment. Were told that this is a typical price for this set-up.
From a cost perspective, the products are close-the Shadin ADC-200 lists for $2995 and the Insight TAS -1000 lists for $3495. If you need a fuel transducer (we didnt), youll need to add another $400 to $800.
But if your avionics shop includes the cost of Insights dealer kit (Shadin doesnt have a dealer kit), you could be stuck with a much higher estimate or final invoice.
Theres no argument that the Insight TAS-1000 offers more features and is more technically advanced than the ADC-200.
Also, the TAS-1000 looks great and the Windicator is a neat unit, which conveniently displays winds aloft and other wind information to the pilot. But until Insight gets avionics shops to actually install the product at a reasonable price, we cant tell you to buy it.
Thus, for now, we recommend the Shadin ADC-200. The ADC-200 is tried and true-avionics shops like the unit, have repeatedly installed it, know it works and recommend it.
Moreover, the fact that the Garmin techs like the ADC-200 and had favorable things to say about it and nothing to say about the TAS-1000 makes our recommendation that much easier.
Also With This Article
Click here to view “Checklist.”
Click here to view “Air Data: Standard in the Future.”
Lionel Lavenue is a frequent contributor to Aviation Consumer. He owns a newish Cessna 206 that has been grounded by the Lycoming crank recall.