Black Box Basics

Getting a handle on the portable GPS receivers.

Global Positioning System technology has brought us some pretty wonderful ways to navigate. Where five years ago, many pilots could hardly have imagined life without the loran receiver, today's aviator is positively starstruck by GPS. Accuracy, simplicity, reliability, and the ability to go there direct make the current crop of GPS receivers so desirable.

The Federal Aviation Administration is taking a shining to GPS, too, and is moving at virtual light speed toward approving GPS as a bona fide navigation tool. (Currently, the Department of Defense has yet to declare GPS operational, but that doesn't seem to matter to pilots; some 1,000 new GPS receivers are being installed every month worldwide.)

Not only is GPS an accurate and reliable navigation aid, but the electronics involved lend themselves readily to miniaturization. We now have hand-held receivers that sacrifice virtually nothing in terms of features, and yet can be connected to the control yoke or placed on a lap board; the boxes are a real revelation to the renter-pilot. What's more, hand-held GPSs have become the price leaders in the field, placing satellite navigation in the hands of many more pilots.

One question frequently asked about any kind of portable navigation system is: How does it really work in the airplane? Our experience with portable loran units, for example, has been mixed, with some receivers working adequately and some not at all.

The good news about GPS is that the format functions wonderfully in the portable iteration. All the GPS antenna needs is a relatively unobscured view of the sky — and many of the units listed here work surprisingly well buried in the cockpit, on a yoke mount or even on the passenger seat. For the most part, the carry-along GPSs perform admirably on their own power, cutting the cord on lighter-plug dependency.

Four manufacturers came early to the portable party, Garmin (formerly Pronav), Magellan, Sony, and Trimble. We have looked at Garmin's Model 100 AVD ("Black Box Basics: Garmin GPS 100 AVD," October 1991 Pilot), which can be used as both a portable and as a panel-mount; Garmin's new unit, the GPS 55 AVD, also a portable, is an adjunct to the 100, not necessarily a replacement. Trimble has been offering various versions of the TransPak portable since 1989, but it has been one-upped by the company's newest portable, the Flightmate, which we'll talk about in a moment.

Among the portable units now available, there is a clear distinction between those designed (or suitably reconfigured) for aircraft missions and those intended mainly as general-purpose or marine uses. Neither Sony's Pyxis receiver nor Magellan's GPS Nav 5000 were penned as aviation units, and it shows.

Take the Sony, for example. Though packing the trade name of that consumer-electronics giant, the Pyxis remains out of its league in an airplane. In the most basic terms, the Sony works fine, picking up satellites quickly and tracking reliably; on the face of it, there's no argument here. But the Sony's operating logic is confusing, making for many trips to the user's manual to decipher the various modes and screens. It has no "direct-to" function; to navigate to any of the user-inputted waypoints (it has no database), you must load in a flight plan and then activate it.

What's more, the Sony shows bearing to the waypoint and vehicle track in true north, not magnetic, which adds to the mental arithmetic. Finally, the Sony has a truly voracious appetite for batteries — enough to keep the Energizer bunny hopping 24 hours a day. About two hours' endurance is the limit from the four AA alkalines, so pack spares in your flight bag. Suggested retail on the Sony is $1,395, but it's widely discounted to under $1,000.

While Sony went for a futuristic look for the Pyxis, Magellan gave its Nav 5000 a more traditional looking rugged rubberized plastic body with an alpha numeric keyboard and large LCD screen. The keyboard makes for easy entry of waypoints and manipulation of data. Another dozen large, clearly marked keys are used to access various modes such as navigation and route.

As with the Sony, Magellan offers no "direct-to" mode. You must first build a route of at least two waypoints, but the Magellan does gives you the option of displaying data in reference to either true or magnetic north pole. Building a route is simple and only requires a few keystrokes per waypoint, once the waypoints have been stored.

The Nav 5000 comes with a cigar-style antenna attached. Unlike the disk antenna on the Pyxis, the Magellan's antenna cannot be removed for easy positioning in the cockpit. In or out of an airplane, we could never get the Magellan to acquire four satellites for a three-dimensional position for more than a few minutes at a time. In the 2-D mode, the user must enter an estimated altitude; information which, of course, is readily available in an airplane.

The manufacturer reports the Nav 5000 will take 10 hours to run through a set of six alkaline batteries when in the battery saver mode. In that case, the system computes a position for about two minutes after a function key is touched. After that the unit stores the latest position information and shuts down. Pilots will likely find that cumbersome, but in the continuously active mode, the Nav 5000 will drain a set of batteries in about four hours or less. Magellan's suggested retail price is $1,199, but the Nav 5000 is available in catalogs and marine and pilot shops for $1,000.

While the Sony and Magellan show their marine roots quite clearly, it is equally evident that the Trimble Flightmate and the Garmin 55 AVD have been designed for the cockpit from the start. Also, they are what one might call second-generation designs, clearly better than the originals and packing an impressive combination of features and performance. Both have built-in databases that are, if not all-encompassing, a far cry from the enter-it-yourself school.

Shaped like an aerodynamic remote control, the Trimble Flightmate is a follow-on to the company's general-purpose Ensign, albeit with considerably different features packed inside the receiver's sleek shape. Its three-channel receiver can track up to eight satellites and presents its information on a four-line liquid-crystal display noteworthy because of the amount and organization of the information presented therein. On this display, you get: destination waypoint identifier, bearing and distance to it, groundspeed and track, Zulu and enroute time, CDI and cross-track distance, and even a display of appropriate cruising altitude as "ODD" or "EVEN." And it doesn't even look crowded; take a few minutes with the Trimble, and you can glean any bit of the displayed data quickly. Kudos to the Trimble engineers responsible for the Flightmate's display.

Trimble also traveled an alternative road in designing the control scheme. Seven function buttons plus a power control grace the Flightmate's face — that's it. Four cursor keys help move from mode to mode and offer the sole method of telling Flightmate where you want to go. The key with the small diamond on its face is a command key, opening up sub-menus; the curved arrow is analogous to an enter key, and the segmented-circle key is the direct-to gateway.

It sounds far more complex than it is. Scroll with the left and right cursor keys through seven sub-menus, Nav (the basic navigation page), Wpt (waypoint information), Near (for nearest airport or navaid), Trip (for the trip timer), Time (access to one of three timers), More (for computations, customizing, and satellite data), and GPS (for present position). To go direct, punch the direct-to button, and the Flightmate prompts you for waypoint type (airport, VOR, or user) and identifier. You scroll through the alphabet with the up and down cursor keys. Although this input method might sound fussy, once you've done it a few times, it becomes simple and quick.

Perhaps the greatest obvious difference between the Flightmate and Garmin's GPS 55 is the keyboard layout. With the 55, Garmin uses a 20-key alphanumeric keypad with the functions printed right on them. And as with the 100, you enter a waypoint's identifier by first punching the key on which the letter is presented, and then skewing left or right with the arrow keys until the correct letter or number appears in the window. For an "S," you'd punch the key marked "STU7," a T would appear on the display, and then you'd hit the left arrow to change that to an S. Again, it's more difficult to explain the process than to actually perform it.

Other features like nearest-airport search live under the Nav, Wpt, Rte, and Msg/Set keys. If you've used the Garmin 100, you'll be instantly familiar with the 55, and even if you have seen neither, your education in "buttonology" should be brief.

Garmin won't tell how many channels live inside the 55's receiver set, claiming proprietary scanning/sequencing software. Frankly, we don't care if it's got one or a dozen; the Garmin system works and works well. It's kind of like asking how many speeds your blender has — if it makes good margaritas, who cares?

Both the Trimble and Garmin units have features pilot have come to expect, like nearest-airport search (as well as a continuously updating scan of nearest VORs and user-defined waypoints), backlighted displays, and useful databases. The Trimble's database is worldwide, consisting of public-use airports with runways 2,000 feet long or greater and VORs. Garmin's database is split into North and South America and the rest of the world and covers airports with runways 1,000 feet long or more and VORs. Neither database includes intersections, airport information beyond location, or other navaids. Both have memory available for user-defined waypoints — 255 for the Garmin, 100 for the Trimble.

While several philosophical differences mark the Garmin and Trimble units, both work exceptionally well. In a high-wing airplane, both GPSs work well simply mounted on a yoke clip. (The Trimble comes with a well-crafted mount; the Garmin provides only a plastic cradle for the 55.) Slight turns and frequent movement of the control wheel will usually result in loss of one satellite, but without fail, these units would navigate accurately and reliably from that less than ideal position. A small advantage falls to the Garmin for its movable, cigar-shaped antenna, which can be tweaked for optimum angles, where the Trimble's built-in antenna cannot without moving the whole unit.

This slight advantage was further exploited by the Garmin in the Mooney 231 also used for testing. Sticking a hand-held GPS on the Mooney's yoke has got to be one of the worst-case scenarios, though, because there's precious little window area and plenty of signal-sapping metal around this location. Here, the Trimble had difficulty obtaining satellite lock, while the Garmin would readily go into two-dimensional coverage but could not pick up enough satellites to reliably provide 3-D accuracy. Placing either unit on the glareshield resulted in quick, full-coverage reception, however.

For those pilots renting Mooneys or other airplanes where the devices won't work well on internal antennas, both Trimble and Garmin have answers. The Garmin's antenna can be disconnected and placed on a suction- cup bracket; it is then connected to the 55 with a short length of coaxial cable. This arrangement is simple and effective. What's more, the antenna seems none too sensitive to position in the windshield, gaining good coverage from several locations.

Trimble also offers a remote antenna, but its execution is, frankly, clunky. To use the external antenna, you slip a small shoe over the Flightmate's snout and connect a lead to the puck-shaped antenna. But that shoe contains a signal preamplifier, and it needs power. So you must plug in the lighter-socket adapter to make it all work. And while you're doing that, you might as well use the battery eliminator, which requires another wire strung from the preamp shoe to the plug that slides in where the alkalines usually go. This clump of connectors turns a truly elegant piece of navigation gear into something less so. Trimble says it is tweaking the Flightmate, and provisions for an unpowered remote antenna would be a worthy achievement.

Either unit will do well on its own battery power. Both companies claim between five and 10 hours' endurance for their respective receivers, and we found six to eight hours a good, reliable figure. Count on slightly less if the battery-saver features aren't used; in any case, these two do much better than the alkaline-hungry Sony.

And while both receivers have battery-saving modes, only the Garmin can be set to an automatic mode; here, it continues to update quickly if it senses the airplane moving rapidly but then shifts down to a slower update rate if course and speed appear steady. The Trimble's can be switched to either the normal or slower update rate. In neither case was there much degradation of performance with these functions invoked.

In most respects, the differences of the Garmin and Trimble GPS receivers are just that — differences. In the vast majority of the units' functions, you can't really call one better than the other. Both are astonishingly accurate and easy to use.

If we had to pick one, it would be the Garmin, by a hair's breath. This is by dint of the elegant external antenna and the data port, which the Trimble does not possess. And then there's a slight price difference, in favor of the Garmin. List prices run $1,295 for the Garmin 55 AVD ($100 less for the non-database model) including external antenna and power/data cable, and $1,295 for the Flightmate (add $295 for the antenna/battery eliminator package). But then the Trimble is appropriately spacey looking and has the better display, both in terms of legibility and in the way the information is presented.

Frankly, the differences are relatively minor, and the pilot using rental aircraft (or even those seeking a backup navigation source for their own airplanes) would be happy with either unit. Isn't this GPS technology wonderful?

Garmin Communication & Navigation, 9875 Widmer Road, Lenexa, Kansas 66215; 800/800-1020, 913/599-1515.

Magellan Systems Corporation, 960 Overland Court, San Dimas, California 91773; 714/394-5000.

Sony Corporation of America, Sony Drive, Park Ridge, New Jersey 07656; 201/930-1000.

Trimble Navigation, 2105 Donley Drive, Austin, Texas 78758; Sales, 800/767-8628; Product Support, 800/487-4662; Service, 800/487-4689.

A Moving Experience

Watching the world go by byte by byte

BY THOMAS B. HAINES

As noted above, owners of aircraft with limited panel space and renter- pilots need not forego the advantages of GPS navigation. The portable receivers make wonderful additions to the cockpit. But two companies have gone one step beyond the stand alone portable receiver to develop portable moving maps.

In its earlier renditions, Peacock Systems relied upon someone else to provide position data for its LapMap moving map software. The latest versions of the software will still accept data from about any panel-mount loran or GPS receiver on the market, but now the company offers its own receiver setup, which can be permanently mounted under the panel or left in a portable mode.

PS Engineering, known for its line of top-quality intercoms, recently joined in by offering its own portable receiver package, the GPSpac, which shows its position via the Peacock software.

Both companies are touting their systems on the new Hewlett Packard 95LX palmtop computer. The powerful but tiny HP 95LX is beginning to make all sorts of inroads in aviation. Paragon Technologies has found a successful niche marketing its FX-7 flight planning software on the 95LX (see "Pilot Products," February 1992 _Pilot_). And Paragon itself recently introduced moving map software for the 95LX that complements the flight planner, though it offers no receiver of its own.

What you get with the PS Engineering and Peacock systems is a RAM card that slips into the 95LX, a receiver and antenna or receiver/antenna combination, and, if you don't want to use a portable battery, a connector cable for the aircraft cigarette lighter. The RAM card contains the Peacock moving map software and airspace database. In both cases, you must buy the 95LX separately.

The first time you use the software, it will automatically load the necessary files onto the 95LX. Also that first time, you select which receiver you are using, and from there out, the two systems are virtually identical. In fact, the only difference we could note is that, when using the Peacock receiver, you are able at any time to display the status page showing data about the satellite reception — a handy feature when the system occasionally has problems locking onto satellites. When using other than the Peacock receiver — either the PS Engineering receiver or a panel- mount — the page is displayed only until enough satellites to compute a position are found. After that, the page is inaccessible.

We won't go into great detail about the Peacock software here. We've written about it twice before (see "Pilot Products," July 1991 and December 1989 Pilot). Suffice to say the software has been improved over the years and is better than ever and easier to use. It accurately displays navaids and airports along with special-use airspace and other controlled airspace as the flight progresses. The LapMap database is more complete than in the hand-held receivers. It includes coordinates and frequencies for airports and VORs and additional information for airports, such as fuel availability and runway direction and surfaces.

On the hardware side, the PS Engineering system is definitely designed for the portable mode. The receiver and antenna are neatly packaged in a plastic case about the size of a James Michener paperback. One cable comes out of that box, splits and goes to the 95LX and either the cigarette lighter or the optional battery pack (which is about the size of the receiver/antenna box and holds 10 AA alkaline or nicad batteries). The receiver/antenna box can be tossed on the glareshield, where it gets a maximum view of the sky.

The Peacock system works fine in the portable mode but is a bit heavier and more cumbersome, especially if using the rechargeable battery pack. The antenna — similar in design to the external antenna on the Trimble Flightmate — can be placed on the glareshield. A wire runs from that to the receiver, which can be placed between or behind the front seats. Two wires emerge from the receiver — one to the 95LX and the other to either the battery pack or the lighter. Peacock officials admit the system was mostly designed as a permanent installation. In that case, the receiver is mounted under the panel or in an aft rack and connected to the aircraft electrical system; it receives its signals from a roof-mounted antenna. Only a small connector is needed on the panel, to which the computer cable is connected.

I used the Peacock system on a recent round trip between Frederick, Maryland, and Dallas. The receiver's battery pack lasted about six hours. After that, I left the 95LX in dead-reckoning mode, which allows the software to continue displaying position as long as you manually enter heading and ground speed information. Before the batteries packed it in, the receiver managed to find enough satellites to determine a position most of the time. The speed and position information was usually within a tenth of a mile of that displayed by the panel-mount GPS receiver aboard the aircraft.

Our experience with the GPSpac also shows it to be very accurate and reliable. The receiver acquired satellites quickly and never failed to find enough space vehicles for navigation during our brief exposure to the unit on the West Coast.

Not surprisingly, the moving map capability does add to the price tag, compared to the stand-alone GPS receivers. The GPSpac system sells for $1,883.95, which includes the receiver, LapMap software, and cables. The rechargeable battery pack is another $189.95. The comparable Peacock package, meanwhile, lists for $2,229. The battery pack is $169. In both cases, you'll have to add on about another $400 for the 95LX, though it is useful for other duties as a personal planner.

Both systems require a fair amount of wire stringing in the cockpit, but in exchange, they provide an excellent situational awareness tool, leaving the user with no excuse for stumbling into a TCA uninvited.

PS Engineering, 9800 Martel Road, Lenoir City, Tennessee 37771; telephone 615/988-9800.

Peacock Systems, Civil Air Terminal, Suite 325, 200 Hanscom Drive, Bedford, Massachusetts 01730; telephone 617/274-8218.