With IFR certified GPS becoming more or less a standard item in the panel these days, the lowly indicators that provide the needles to follow have become more important than ever. And whether good or bad, there are more choices than ever in indicators but not a big knowledge base on what indicator works with what box.
The tricky part of this business is that many owners assume they can use the old indicators with a new navigator but are shocked to discover theyll have to shell out another $1500 or so for a nav head because the ones they have wont play with new equipment. In this article, we’ll cover the particulars.
Since all IFR GPS, whether installed for approach operations or enroute, must also display course information on a remote CDI, you cant get by without an indicator of some kind. On the plus side for the price savvy buyer or owner with tight panel space, the ability of the GPS and navigation receiver to share the same indicator has become commonplace and is often the only solution aside from cutting a new instrument panel. In some-perhaps most- cases, it makes sense to think about an HSI in place of a standard indicator.
Were the first to recommend utilizing as much of your existing equipment as feasible while acknowledging that some of this stuff just wont be worth keeping. Beware, however, that not all indicators will support all GPS navigators, even though the indicator itself is ship shape. Some older indicators wont support any so youre stuck buying new ones.
The specs for appropriate nav indicators are critical whether youre choosing one for GPS or for old-fashioned VOR. Technical criteria such as OBS course resolver, VOR/LOC converters and the like must be considered in almost every case, so your shop techs experience and knowledge of new and old equipment specs is critical. Otherwise, you could end up spending far more money than you planned or spending less for a panel that doesnt work correctly.
Indicators First
Many customers who spec avionics upgrades on the back of an envelope are shocked when they learn theyll have to spend another 15 percent of the budget for indicators. When deciding on upgrading a navcomm-even if you decide to purchase a used system such as the ones we mentioned in the used equipment roundup in the January issue of Aviation Consumer, its not a bad idea to start with the indicator, selecting one that will support your GPS of choice.
If the indicator is to be shared-utilized with a nav radio for LOC/GS and for GPS area navigation-consider it one of several critical components in this interface.
The overall concept of sharing a CDI is simple. The GPS navigator and nav receiver are often tied to one indicator via a remote relay and ideally controlled with a push button annunciator.
Some interfaces control this command with a toggle switch while the better ones have a positive-feel lighted pushbutton. The pilot selects GPS or nav and the appropriate source plays on the indicator. In most cases, when a localizer frequency is tuned in the nav receiver, the indicator automatically displays raw nav data.
This is known as an ILS lockout and is supposed to be an idiot-proof safety feature to ensure that you don’t come boring down a precision approach without real ILS data displayed on the CDI.
On the other hand, more than one pilot has accidentally tuned an ILS and locked out the CDI when he really wanted to display GPS data, so obviously the knife cuts both ways. And know this: not all airplanes are wired for the lockout so you always need to check which box is displaying to which indicator. If you tune an ILS in the Garmin GNS series navigators, for instance, the box lets you get as far as the final approach fix while displaying GPS course data but then automatically switches over to the ILS information; an enlightened ILS lockout, if you will.
Some indicators now have an integral annunciator lamp that clearly shows which mode the system is in, which is also a nice touch. Rookie and lower standard installs are easy to spot by simply eyeballing the nav source switching system. You can tell the cheap from the high quality by appearance.
The source-select button should be sunlight readable and comfortable to view at night and be labeled accurately. Be sure your shop fully explains your system beforehand and then demonstrates this switching while on the GPS certification test flight. This switching and annunciation can mean the difference between easy GPS approaches and ones that can be stress fests in cockpit overload.
You don’t have to be techy to appreciate a quality nav indicator and its related systems. Little things such as uniform and comfortable backlighting and fluid CDI movement are most important in our view and the following units we mention score high, if properly installed and calibrated.
The indicators that we believe work we’ll with and are appropriate for most all of the Garmin and Bendix/King GPS navigators and Silver Crown series nav systems include the KI208A/KI209A series. The A is important. A straight KI209 wont work with Bendix/King or Garmin GPS since this is a converter indicator, meaning that it converts localizer signals for the proper scale display.
The KI206 is popular and has proven quite reliable and easy to repair, if repairs are ever needed. Its often found with many existing Bendix/King KNS80 nav system installations, making GPS upgrades less of a budget hit when removing that old KNS80.
Its popularity is evident when you discover that on the used market, the average price is an astonishing $1100 or more in serviceable condition, regardless of cosmetic appearance.
The KI204 and non-glideslope compatible KI203 feature a rectilinear meter presentation, a nicer look than the KI209/208 in which needles pivot, windshield wiper style. But the KI204 and KI203 wont play with Garmin or many Bendix/King GPSs. They will play with KX155 series, making them a good choice for installations where only conventional navcomms will drive the display.
Keeping the Old
In general, we suggest caution in keeping a truly vintage indicator to interface with a new GPS. Customers sometimes ask about the Bendix/King KI214 series indicators that a shop or used avionics peddler has proposed.
These units have built-in glideslope receivers and although this is one way around the remote glideslope problem required with KX170B installations, the indicator is often a dog on the repair bench.
Pass this through your busy avionics shop for repair and don’t expect a warm reception. Although a good design in its day, its dated by modern standards.
Most seasoned bench techs who are savvy to todays modern equipment will feel guilty charging you money for repairs on this stuff. The same holds true for the VOR/LOC only Bendix/King KI201 series, ARC type indicators and the Narco VOA series.
This is tired old vintage equipment and trouble waiting to happen if kept in the panel or, gasp, installed as new-to-you used gear. You wouldnt wire your 30-year-old speakers to a state-of-the-art sound system and you shouldnt try to make a modern GPS system work with KI214s.
Early Collins IND350 series tend to be problematic with picky meter movements which are quite costly. The later models of the Collins IND series heads are often worth retaining but have your shop do the research and appropriate bench eval before you commit.
These heads and most of the Collins Micro-Line avionics are often found in late 1970s and early 1980s Beechcraft and the IND could come in handy for a secondary GPS or nav system.
Narco glideslope and marker beacon-equipped NAV122 and VOR/LOC only NAV121 series indicators are all self-contained nav receiver indicators. These save a lot of panel space since they provide all nav functions in one box. Theyre often found in older Tigers, it seems.
Although a decent indicator and possibly the only choice for space-challenged panels, field serviceability is an issue. As weve reported on Narco radios in general, getting this equipment repaired is not easy and some owners tell us it has been an ordeal.
Earlier vintage 122/121 series units utilized plastic channeling gear mechanisms but the later replacement gears were brass. But if you need the gears, only the factory can do the work. Expect a hefty factory repair bill but probably decent service if youre willing to pay.
The NAV122D, an updated version of the NAV122, is designed for interface with some GPS. If you have to use a self-contained nav like the NAV122, make it a D version. Narcos ID825 and ID824 are reliable and worthy indicators to play with MK12D Navs and a few GPS interfaces.
Remember Terra? Whatever happened to them and their line of indicators? Terra sold out to Trimble Navigation and now Trimble is no more, at least in light GA avionics.
Our reason for mentioning this is the Terra TRI-NAV C electronic nav indicator. This digital design featured LED meters and an interface that allowed sharing with a loran and some GPSs. Some pilots liked the digital design, most did not.
There are a lot of these on the market and they can be had for a song that will even harmonize with some but not all modern GPS. Installation considerations are often challenging for this indicator and with continuing support iffy, we don’t consider it a strong contender.
Clean Sheet
Hands down, our favorite choice if you have to start from scratch and want to buy new is the modern design and current production MD200 series from Mid-Continent Instruments. These are made for and marketed by Garmin and Apollo/UPSAT.
Your shop will know which flavor of this indicator is the appropriate match for your specific interfaces. This nav head also plays exclusively with the UPSAT SL30 navcomm system and is often shared with the companys GX series GPS systems.
Money invested in this indicator is we’ll spent. Its presentation is top-notch all the way with bezel glass so clear it looks to have none at all. This indicator also has a built-in mode annunciation for positive identification of the nav source selected. Thats a nice detail to guard against driving it with the wrong source.
While we agree that trying to utilize as much of the existing equipment is wise, sometimes you just need to spend the extra dollars to get troublefree service. If you have an older nav head thats serviceable but not quite up to snuff, replacing the meter movement and other tweaks will probably exceed $1000.
The average cost of factory new later and greater units like the MD200 and KI209A heads usually adds $1400 on average to most GPS upgrades so you may wish to consider that in your budget.
Conclusion
If money is low on the concern list, we would install an HSI and if that HSI were electronic, say a Sandel SN3308, we would probably back it up with a mechanical nav head for the number-two system.
Many customers are seeing the sense of this and backing up an EHSI with an electro-mechanical head. If we had a full Bendix/King suite with or without GPS, our first choice is the KI209A.
Garmin stuff? The MD200/GI106A because of proven high quality and design features, plus the MD200 series is claimed to support WAAS GPS if and when we see that.
If you hold off on IFR GPS for the short term and simply upgrade the nav system, we suggest utilizing an indicator that will ultimately support GPS. Youll spend a little more now but a lot less later.
In either case, the nav indicator is not a place to cheap out. If youre savvy, its an area in which you could save a little money and end up with reliable, nicer-to-look-at nav guidance.
Also With This Article
Click here to view “Checklist.”
Click here to view “Thought About an HSI?”
Click here to view “Indicator Glossary.”
-by Larry Anglisano
Larry Anglisano is Aviation Consumers avionics contributing editor. He works at Exxel Avionics in Hartford, Connecticut.
