The first IFR GPS box stands the test of time
For many of us, the date February 17, 1994, may not resonate rich with historic meaning. Nevertheless, it was on that day that the FAA certified the first GPS box for nonprecision approaches under instrument flight rules.
The Garmin GPS 155 was the hero of the day, being the first panel-mount receiver to earn IFR approach approval — and, by extension, legitimizing the concept of GPS navigation as something much more capable than the VFR-only, IFR-en route realm that preceded it. So, in large part, the 155 paved the way for other IFR panel-mount receivers to follow.
Guess what? The 155 is still around and still very popular. And for good reason. Of all the IFR-approved GPS receivers out there, the 155 is perhaps the most intuitive to use. Many in the business consider it the unit of choice, not just because of its user-friendliness, but also because it still offers the most bang for the buck. At $4,995, its price is almost half that of competing top-of-the-line receivers. (Translation — take a deep breath — AlliedSignal Aerospace Commercial Avionics Systems' Bendix-King KLN 90B, which goes for a healthy $8, 595.) However, the 155 does compete directly with Bendix/King's KLN 89B, an IFR approach-approved GPS box with a built-in moving map and a $4,895 price tag.
To any of these prices, add $1,500 or so for the cost of installing the receivers, annunciators, and antennas.
The most appealing aspect of working a 155 is that the buttons mean what they say. "Direct," "NRST," "SET," "RTE," "WPT," "NAV," "CRSR," "MSG," "CLR," and "ENT" are about as plain as day in their meaning. Want to know the nearest airports? Hit the NRST button and scroll through the nearest nine with the inner knob at the box's lower right corner. Hit the button again for nearest navaids, again for intersections, again for special use airspace, again for flight service frequencies, and again for user waypoints. On all of the lower keys you have a choice of hitting the key again and again to bring up various menus or functions, or scrolling through them with the outer knob. So whether you're a button-pushing or knob-twirling kind of person, you're in luck with a 155.
Data entry is facile, too. Once in a function, hit the cursor button to start an entry prompt flashing. Use the inner knob to make the first character entry, the outer knob to move to the next character, the inner knob again to make the next entry. When finished with the entry, hit ENT to finalize it. Keep moving to other entry fields by using the same combinations. After a half-hour of practice in simulator mode, you've got the hang of it.
A very nice feature of the 155 is that it brings up the initial letter "K" as a default when making flight plans or selecting airports as waypoints. This keeps you from too much knob- spinning, which can be frustrating during times of high workload.
Yet another major standard feature is a battery backup. In case of complete electrical failure, the 155's internal battery is capable of powering the unit for as long as 90 minutes. This potentially life-saving feature is just plain unavailable on most other panel-mount GPS units.
Of course, just like all of its competitors, the 155 has all of the E6-B functions that you'd expect of an IFR-certified box. Its greenish, vacuum fluorescent display is easily visible in even the brightest sunlight, and it uses a Jeppesen database that includes airports (and their runway information and communications frequencies), navaids, intersections, minimum safe altitudes, and special use airspace. There's even a place to enter customized checklists (it's in the NAV function).
Approach navigation chores are simple, compared to those of some other units. First, make sure your destination is an airport, then use the RTE button, the outer knob, and cursor and enter keys to select both the nonprecision approach and the initial approach fix. Arm the approach mode by pushing the GPS approach ARM/ ACTV annunciator switch. As you fly toward the IAF, the 155 will autosequence through the successive fixes. If you'll be flying a holding pattern, flying vectors, or flying a full approach with a course reversal, hit the GPS/APPR annunciator switch to illuminate its HOLD light and suspend sequencing. Once turned around and heading back toward the airport on the final approach course, hit GPS/APPR again to reactivate the autosequencing. Then fly the approach as you normally would. Lateral course sensitivity ramps down to 0.3 nm (for a full-scale deflection) as you approach the runway threshold, so beware of overcorrecting.
It's all fairly easy, once you practice a while — in VFR conditions.
Garmin makes a companion receiver to the 155 that's also IFR-certified and comes with a built-in transceiver. This model, the GNC-300, operates in virtually the same way as the 155 and costs $5,495 for the IFR-approved version. The GNC 250 is a $3,250 VFR variant. The communications radio flip-flops frequencies from standby to active mode, and there are a few other appealing features to this aspect of the unit — battery backup, automatic squelch, stuck microphone protection, and quick-tuning of 121.5 MHz being the most prominent. These have been discussed in a previous article (see " Pilot Products," August 1996 Pilot).
The com radio makes the 300 a taller box than the 155, but this is a tiny tradeoff for the capabilities gained. For example, those who buy a 300 can buy some panel space if they do away with an existing com and nav radio and use the 300 as their primary navcom. Brilliant in concept, the 300 remains (mysteriously so) one of Garmin's least-sung-about achievements, and a hint at what's next around the bend in Garmin's product line.
What don't the 155 and 300 have? A moving map and more than three or four lines of information on any one display lead the list.
Proponents argue that a craving for a moving map — and for deep-sixing your old ADF head and receiver box — can be satisfied by adding to your panel an Argus 3000 ($2,995) or 5000 ($4,995 — it has IFR approval) and using the Argus as both moving map and legally surrogate ADF indicator. Extracting your second VOR can free up the panel for lightning detection, engine monitoring, or other instruments. Cost? A 155 and an Argus 3000 come to approximately $7,990 — about $600 less than a KLN 90B.
Garmin isn't the only manufacturer trying to bolt an add-on moving map to plain-Jane IFR GPS receivers. II Morrow's combo package comprising its IFR-certified Apollo 2001 GPS and its 360 MAP moving map, will run you $4,995. Trimble's marriage of its IFR-certified 2000 Approach box with an Argus 3000 moving map will set you back $7,890; with the Argus 5000, the total price goes up to $9,890. So the Garmin/Argus option is definitely very competitive in price for those who feel that they absolutely must have a moving map.
In the fast-moving world of GPS applications technology, manufacturing, and regulatory busywork, it's becoming more and more difficult for the aviation community to anticipate the true shape of the all-GPS navigation world of the future. Manufacturers try to outdo each other in offering more and better features. The FAA sets policy based on equipment and capabilities of a few months ago — an eternity for GPS manufacturers, given the pace of change.
In the middle are the pilots. You and me. Wanting value from a GPS box, wary of changes that will make today's buying decision tomorrow's regret, and not having a whole lot of money to throw around on spec.
A current source of speculation centers on the nature of the so-called "end-state WAAS" world. WAAS stands for Wide Area Augmentation System, a methodology whereby GPS satellites and ground stations provide more exact signals to those aircraft with GPS units capable of receiving them. Under this scheme, airplanes with WAAS boxes will be permitted to shoot precision GPS approaches to Category I limits — i.e. the 200-and-1/2 conditions currently prescribed as minima for many ILS approaches.
Furthermore, when WAAS comes, ILS is supposed to go, as in universally decommissioned.
WAAS-world, we'll call it, will begin on or about the year 2001 (cute, eh?) — if current plans hold up as advertised. (They won't.) Anyway, at issue is the future of all those thousands of IFR, nonprecision approach-approved receivers currently in service. Those without upgrade paths won't be able to receive WAAS signals and therefore can't be used for precision approaches unless some serious hardware and software changes are carried out. ILS is gone, so that's not available.
But if non-WAAS boxes like the 155 and 300 can't be used for precision approaches, they can continue to give excellent service on nonprecision instrument approaches for the indefinite future. As it currently stands, the FAA has no plans for a WAAS-only world.
Plans to severely reduce the number of VOR stations, however, still remain in effect. The upshot: In 2010 or so we'll all need redundant, non-VOR backup equipment capable of both en route and approach navigation to supplement our WAAS boxes.
This all spells longevity for the Garmin 155 and GNC-300. Given the uncertainties and transitional confusion that will attend the advent of WAAS-world, trusty, friendly boxes like the 155 and GNC-300 will be welcome sights in any cockpit of the future.
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