GPS on the Cheap

Well-heeled owners are starting to dump used navigators. Heres how to pick a gem out of the soon-to-be glut.

In the world of GPS equipage, weve noticed an interesting trend lately. For want of a better term, we’ll call it the have and have-not syndrome.

The haves are buying up Garmin GNS 430s as fast as Garmin can make them while the have-nots are eyeing all the hand-me-down GPS boxes many of these owners are dumping to accommodate new gear.

Given the volume Garmin is enjoying with GNS 430, this is a somewhat unprecedented development in the recent history of avionics. Some of these GPS navigators were installed less than two years ago and although their owners consider them obsolete, the fact is, these units are serviceable, if somewhat poor in features compared to the newer stuff.

Good Deals? Yes
There are good deals out there in used GPS, no question. But also some pitfalls when you consider that in adding up the bottom line for installation, indicators and annunciators, you may be pushing $6000 for one of these used navigators.

Thats not so bad if you plan to keep the airplane for a few years and are sure you wont want to upgrade to something colorful and expensive in the short term.

Its not a good idea to spend that much if youre remotely considering selling the airplane soon or youre awaiting next falls product intros. Save your pennies for something state-of-the-art.

But lets say youve visited your shop for some tire kicking and…whats this, the shop has a couple of used KLN-90Bs for a good price. ($3000 is a good price.) What are the pros and cons of sticking one of these vintage boxes-if a three-year-old GPS can be called vintage-into your panel?

Instant IFR GPS for a bargain price, including approaches.
Legal substitution for DME and ADF.
A quick hit, usually, with no major panel surgery.
A serviceable box for the foreseeable future.

No upgradeablity when WAAS finally happens.
Except for the Northstar, difficult operating logic.
No fancy moving map or other high-end features.
Limited warranty coverage.

All things considered, thats not a bad balance sheet, depending on the box, the price and what your future plans are. Herewith is a box-by-box rundown on whats out there. But first some general advice on buying used.

At the time of installation, plan on purchasing a factory new installation kit, and factor this into the bottom line. New connector kits are a must, since a little extra money spent here will avoid problems later, obviating the chore of tearing open the panel to find a loose wire.

Have the system sent to the factory for a check, if it hasnt been back within say, six months, or if you otherwise have any doubts about its condition. Its important that operating software and internal GPS clock batteries are fresh. don’t forget that these used GPS units could be as old as five years and better to get the board up to snuff before you put it into your airplane.

Also, plan to purchase at least one database revision, even if you don’t buy a subscription. If you certify the used box for IFR, you’ll need a current database for the required flyoff.

All first-generation IFR GPS navigators require the use of a remote indicator and mode annunciation of some kind. If you didnt purchase your system with a remote indicator and/or annunciation, you’ll pay for it at installation time. Make sure its included in your bottom line price, since this can add $600 or more to the basic cost of the box.

All IFR GPS will display steering (Left/Right/FLAG) information compatible with most relatively modern HSI systems, if the aircraft is so equipped. This eliminates the need for a separate indicator but it doesnt solve the annunciation requirement.

At this point, a remote combination switching relay (ACU or Annunciator Control Unit to switch NAV/GPS left/right/flag info) will be needed. Some owners-mainly the Luddites still clinging to their ancient lorans-have trouble grasping the remote indicator concept. But from the wiring and installation point of view, its significant and a major item on the list of things that drive up the cost of GPS installations certified for IFR.

The installer must use RG-142 low-signal-loss antenna cable and the IFR GPS must be coupled with the altitude digitizer for altitude input. you’ll also want the system interfaced with your autopilot system for nav tracking, another reason for the remote ACU if tied to the HSI.

If you don’t have a cooling fan system, now is the time to bite the bullet, as most IFR units require forced air-cooling. Its a cheap insurance against other avionics failures, too. If you have an aircraft with a right-side avionics stack, you may not be happy having the GPS installed there. Plan on relocating stuff out of the main stack to make room and get an estimate from the shop on doing this.

GPS approaches work best when the pilot has full visibility and easy reach of system controls. In fact, the FAA requires as part of a TSO C129 (A1) approval that the remote annunciators and indicators be within the pilots IFR scan. (Some FSDOs are liberal in interpreting this, others are not.) The installation facility-and it must be a FAA Certified Repair Station-must test fly the system in order for it to be approved for IFR. A maintenance shop installing IFR GPS will get the FAAs attention. So unless you have no intention of certifying it for IFR-and nothing says you have to- have the work done by an experienced radio shop.

The point here is that all of these factors will affect the cost of having your used GPS system installed and a good working relationship with the installing shop is essential. But know this: That nice little M3 an owner is willing to let go for $3000, might cost another $1500 to $2000 to install. More if the shop runs into trouble when reshuffling the panel. A lot more if you need to replace your older HSI.

Of course, theyd have the same trouble if you decided on new equipment. But a box like the Garmin GNS 430 requires less hardware than some of the original IFR navigators so the difference in installed cost is not always as great as some owners imagine. As with all used equipment, someone got rid of the system for a reason. Either an upgrade to later and greater models or the previous owner didnt like the equipment due to its unfriendly operation or some other factor. Or perhaps the unit was a lemon and plagued with problems. All are reasons to move on to something else, which is commonplace with IFR GPS. It will become more so in the next two years.

don’t be afraid to ask about the history of the unit. Most KLN-90Bs, for example, came out of higher end aircraft and cost $8000 to $9000 to install, or more. Owners of this class of airplane routinely upgrade and thus often get rid of perfectly good avionics.

Most important, make sure the system is fully functional (especially the antenna) before installing. The installing shop has no time to chase their tails after an installation only to find the equipment is at fault. And you will pay if they do.

Choices, Choices
Whats out there? A lot of variety but not always lots of volume. Supplies seem spotty but we expect to see much more of this equipment flooding the used market this year. Here in no particular order are some sample boxes, with our comments on each.

Garmin GPS155-The GPS 155 was the very first stand-alone approach navigator and compared to newer gear, it looks it.

No moving map but a bright fluorescent display that holds up poorly in sunlight. The operating logic can best be described as steam driven, including the manual arming feature that Garmin engineers still chaff over, since other manufacturers were allowed to make theirs autoarming. Still, this box is learnable and took unfair hits for being excessively difficult to use. (Its only mildly awkward to use.)

The external indicator of choice for this unit is the Mid-Continent MD40 series, which has most of the annunciation integral. A remote APPROACH: ARM/ACTIVATE light/switch is required.

The Garmin requires OBS course resolver, the most expensive of the indicator types. (Resolving-type indicators work like VOR indicators, in that turning the CDI centers the needle. Resolverless indicators are driven solely by the navigator; the OBS has no effect.)

The HSI will also need a resolver. Some of the earlier Sigma-Tek/Sperry units didnt have one, something that comes as a shock to an owner who now has to buy an HSI or install another indicator. The GPS155 will also play with 3-inch indicators such as the King KI-206, KI-202 and KI-209A and Collins IND-350.

Obviously, these indicators don’t have integral annunciation (except KI-209A) so remote lights are needed. We like the high-quality, sunlight-readable Eaton 582 series switch/annunciators but there are cheaper types available. The GPS155 requires the Garmin GA56, an amplified low-profile design.

Bendix/King KLN-90A/KLN-90B-Bendix/King rapidly followed Garmin into the market, first with the KLN- 90A and then the KLN-90B. The KLN-90A is en route certified only and will drive most indicators accepting steering info. It needs a remote MESSAGE/WAYPOINT annunciation.

The KLN-90B was made in several variants, including 14- and 28-volt models, black or gray bezel and 5-volt lighting. Be sure to check voltage when purchasing these units. Most switching boxes are also voltage sensitive, as is the internal lighting in the MD-40 indicators. (The other units mentioned here accommodate any input power voltage.)

Like the Garmin, the KLN-90B is also an OBS resolver design and will interface with the same indicators as the Garmin. The KLN-90 series is large (in depth) and is often a tight fit in crowded panels. Got an older Bonanza? This box will go in the center stack only with care if at all. Find out before you buy one.

Antenna selection is important, as some of the older KA-92 types werent TSOd. If the antenna is old, plan on buying a new KA-92, which is also an active, low-profile antenna. The 90Bs run hot so budget for a cooling fan, if you don’t already have one.

As noted with the KLN-88 Loran, the CRT displays will quit at mid-life if not cared for-meaning cooling-so before you buy a 90B, price a new CRT display from the factory, just to get your game face on if you need one.

Or… get a factory-overhauled unit, complete with new installation kit. It will cost more but it will also carry a warranty, which a unit bought on the open market may or may not have. (Shops generally offer warranties on their own work of three to six months. But ask specifically, especially if you show up with a navigator you bought from another owner or an ad.

When installing a KLN-90B, plan on the installation of a remote RS-232 data port for updating the database.

The KLN 90 has a rear-loading data cartridge that requires removing the box for revisions. This was never a good idea, since its hard on the pins and tray and is a pain in the butt anyway. (Not that updating through a laptop is necessarily easy, either, but it causes less wear and tear on the GPS itself.)

The KLN-90B is a current production box, although not a strong seller against new stuff from Garmin and Apollo. That means there’s no problem with support for the foreseeable future, even if Bendix/King has drawn some brickbats for declining product support in general. Logic wise, its middle of the road. Some find it easier to use than the Garmin 155, others consider it more difficult. Although it has a moving map, the display is rudimentary and-a big complaint-it doesnt show special use airspace. (The box itself does have text SUA alerts, however.)

KLN-89B-This is another current production box rapidly being outpaced by the color mapcomm offerings. But in its day, it was a best-seller and had both Garmin and Apollo on the run three years ago. (In GPSs, a dogs day isn’t very long.)

The 89B has an improved GPS engine and upgraded software, although its operating logic is almost identical to the 90B, which is to say reasonably easy to learn.

The display is reddish dot-matrix gas plasma design thats adequate but obviously outclassed by new generation color displays. (It does, however, depict special use airspace.) The crap shoot here is that Bendix/King will release the KLN-94, a color follow-on box, sometime this year. If KLN-89B owners take the bait, we could see more used ones on the market. Even if they don’t go for the conversion, the Garmin GNS 430 will certainly shoulder aside some 89Bs.

Like the 90B, the 89B requires an OBS resolver. Early units had growing pains-seized function knobs, RAIM problems, display troubles. Service mods address most concerns, so a factory reman is once again the best bet. If you buy on the open market, check the mod status for currency.

Apollo 2001GPS/2001NMS-Although it seems hard to believe, at one time in the not-too-distant past, it was thought that GPS and loran formed a marriage made in heaven. IIMorrow-now UPS Aviation Technologies-built boxes in this vein, as did Northstar. The market had other ideas and once GPS got a foothold, loran was left for dead.

The 2001 Nav Management System (NMS) was a GPS/loran-C combination system certified for IFR early on, since loran was approved for en route IFR and GPS wasnt.

The GPS sensor is remotely mounted in the tail or nose or wherever there’s room. This makes installation costly and most busy shops will turn the job down, since there are easier ways to make money and keep customers happy.

The later 2001 GPS is a stand-alone C129 A1 unit, GPS only. It doesnt need an OBS course resolver, so Mid- Continent makes a non-resolver MD40 CDI display with integral mode annunciation-substantially cheaper than a resolverd MD40.

We definitely recommend that these boxes be sent back to the factory for software, memory batteries, and a thorough check over. Be sure to check the part number for C129 A1 capability. A few early ones had the TSO placard but didnt qualify for the TSO. A gray-code converter box or compatible Apollo encoder is required and is made by Shadin. Its quite expensive, too, so get a price before committing. This navigator requires an active GPS antenna, the Apollo A16 for loran or the A33 GPS antenna for the multi sensor system.

The real eye-opener on this unit is price: In GPS only, the 2001 can be bought for roughly $1000, making it the least expensive IFR GPS. But there’s a reason for that. For one, the 2001 was never a popular seller and second, the operating logic is quirky, to say the least. Setting up approaches can be a frustrating exercise unless you stay current. (To its credit, Apollo addressed this problem nicely in the GX series navigators.)

The 2001 does have a readable and highly customizable display, however, and the resolverless design simplifies installation.

Northstar M2/M3-Although its somewhat of a fringe player now, Northstar wrote the book on brilliant operating logic, first with the M1 loran and carried over into the M2/M3 GPS boxes.

The M2 is also a multi-sensor loran/GPS combo. These arent very common since Northstar took most of them back during the M2/M3 trade-up program. The M3 was the first box to truly automate the selection and flying of approaches, something the other boxes never quite managed. (That Northstar came late to the certification party helped, since they benefited from the mistakes of the other companies.)

On the downside, the Northstar display is frozen in time, circa 1988. Not only does it lack a moving map, but its also a single-line display with limited data. But we like it that way! reply the Northstar loyalists. Fair enough; it gets the job done. Just don’t expect anything fancy.

You could, of course, opt for an external moving map, such as Bendix/Kings bargain KMD-150 or even an Avidyne FlightMax. Then again, if youre spending that kind of money, youre probably not a candidate for used equipment.

Installation wise, no warts at all. Like the Apollo units, the Northstar is resolverless and uses a dedicated CDI with the annunciation built in. Further, the box is small enough to fit just about anywhere.

Trimble 2000 Approach-When writing about this box, all we can think of is Marlon Brandos bloody visage and the phrase, I coulda been a contender.

The Trimble was one of the first IFR boxes out of the gate, following the Garmin 155. Although it didnt have the easiest operating logic, it did have some terrific features, including the best designed buttons and knobs of the lot and a nearest approach feature we really liked.

Its display is similar to the Apollo in appearance in content, meaning two lines of text-only display with no map options, other than an external of some sort. The display is very legible yellow LED type. Again, a relatively easy install, since this unit doesnt have a resolver. Mid-Continents MD40-66 series is the indicator of choice.

Trimble turned out to be a lukewarm player in aviation GPS. It introduced a sophisticated handheld in 1994 but never followed up with more products; the kiss of death in this market. Its early panel mount GPSs were we’ll received and developed a reputation for being well-built and reliable.

The company shocked the GA world when it announced in 1998 that it was abandoning the light aircraft market, after having bought Terra to make a run at a full-panel product line. Although Trimble says it will remain in the corporate and airline avionics markets, support for the 2000 is iffy in our view.

We wouldnt say don’t buy one, but we wouldnt spend much for one and would buy only with the idea of replacing it with something else in the not-too-distant future. As a general used buying strategy, that advice applies to most the boxes mentioned here.

Also With This Article
Click here to view the Used GPS Comparison.
Click here to view “Want it Real Cheap? Don’t Certify for IFR.”

-by Larry Anglisano

Contributor Larry Anglisano is a consultant and test pilot at Exxel Avionics in Hartford, Conn.