When you look at that black-and-green RV-6 in the picture above, youd probably assume that given the business Im in (avionics installation for the newbies among you), the equipment in the panel would be top-notch modern glass. The fact is that, like many of yours, my airplane was built quite a number of years ago, and it is equipped with flight and engine instruments of a vintage that just isn’t modern.
This is perhaps one of the most common panels from the pre-EFIS era. What happens when that attitude indicator and/or directional gyro need repair?
Maybe you own a homebuilt like this and now you’re considering panel upgrades with up-to-date (or more modern) equipment. Welcome to treacherous waters. At this point, you need to carefully consider how to best go about the upgrade without breaking the bank or causing the aircraft to be out of service for many months. Before you start unscrewing old instruments, you also need to decide how far you want to go. Is this just an instrument swap with a mind toward increasing capabilities, or do you want to begin a comprehensive upgrade project? I have recently undertaken this very mission, so allow me to share my thoughts with those of you facing the same questions.
As I have said many times before, you need to define your mission and appreciate your own capabilities at the outset. Please be realistic. If you’re a VFR/sunny-day pilot, think long and hard about how much avgas that upgrade would buy-the VFR package is, by definition, one that requires your eyeballs to do the heavy lifting. VFR pilots don’t need double-screen EFISes, triple-redundant electrical systems, and every bell and whistle in the book.
You should also be realistic about how much actual IFR flying you do, and what the nature of that flying is. If you are a pilot who demands 100% dispatch reliability, and you expect to make virtually every flight regardless of the weather conditions, you are either a complete optimist or you have built a Boeing 737 in your garage. (Who knows…it could happen!)
The Gyro Game
Typically, this is where the process gets started. Your vacuum pump has failed for the umpteenth time, or that electric attitude indicator is beginning to get the leans. It happens. Your hangarmate with the 1972 Cherokee knows the symptoms well.
You have priced replacement and overhaul options for the existing equipment but have decided its time for an investment. The first step is to consider one-for-one replacements-that is, miniature EFISes that fit into the existing instrument hole. There are good reasons for this decision. First, modern digital electronic instruments are many times more reliable than spinning gyros. Second, it can be financially more attractive to purchase a new EFIS instead of overhauling or replacing the gyros or other instruments. Third, you almost always save weight. Lets look at the options.
Dynon reports that sales of the D10A continue to be strong despite the development of its big-screen SkyView system.
Dynon D10A/D6
Dynon kicked this category of instrument into high gear with the original D10 (now replaced by the D10A and the new, lower-cost EFIS-D6). Imagine a full set of instruments that fits in a 3.125-inch hole. While the introduction of the large-screen SkyView models might have predicted the demise of the smaller legacy boxes, Dynon says sales have remained strong for the pre-SkyView units.
The D10A is a self-contained EFIS thats actually simple to install. In theory, you could hook up power and ground, connect the pitot/static lines, and call it a day. The D10A has a built-in magnetometer that works adequately in many composite and aluminum airplanes, but it can also be fitted with a remote sensor that will be placed away from ferrous metals such as the engine mount, landing gear, etc. Its my experience that ordering the remote magnetometer is money well spent.
The Dynon EFIS-D6 is a simplified version of the popular D10A; its intended mainly for backup installations because it lacks some of the connectivity you’ll want as a primary instrument.
Dynons D6 can be considered a de-contented D10A that does without several features for the reward of a much lower price; its $1600 versus $2200 for the D10A. For example, the D6 does not have an HSI, cannot do density-altitude, true airspeed or winds calculations;it doesn’t network to other Dynon products; it doesn’t support Dynons autopilot servos, and it doesn’t include altitude or heading bugs. On the other hand, the D6 comes with the external magnetometer standard-it doesn’t have the internal module. The D6 can be fitted with an internal backup battery, and it supports the use of Dynons pneumatic angle-of-attack pitot tube.
Both the D10A and the D6 are slightly wider than a standard 3.125-inch instrument-the face is 4.09 inches wide, 3.39 inches tall-but they fit most panels well. The depth of the units can be an issue with some aircraft, as the units are about 10 inches deep when installed with the connector and pitot/static/AOA fittings. Still, the retrofit installation of a Dynon EFIS can oftentimes be accomplished in less time than it takes to remove the vacuum system it is replacing.
Heres an example of a panel that might have started with a six-pack layout but enjoys updated instruments and expanded capabilities.
One question were often asked is whether to purchase the D10A or the D6. The answer is straightforward: If you’re simply replacing an attitude indicator and have no external devices to interface with, then the D6 is the best choice. However, if you want to interface to a GPS or radio like the SL30, then the D10A is a better choice. I would also recommend the internal backup battery.
The MGL Xtremes main page is typical of modern EFISes, with tape-style readouts for airspeed, vertical speed and altitude.
Our experience with the D10A has been very good. The device is now well-proven and reliable, and Dynon continues to support it mechanically and through software updates. There’s more than a little something to be said for that corporate attitude.
MGL Xtreme
MGL Avionics has been providing a nice line of EFIS and digital instruments primarily to ultralight and sport aircraft owners for many years. Within the past few years, the company has created some new models aimed squarely at homebuilders that are both feature laden and low cost. The company’s 2.25-inch and 3.125-inch singles have a basic attitude indicator (grayscale black/white) and are low-cost alternatives to gyros. They are easy to install and lightweight.
A VFR screen allows presentation of basic information.
While the singles are popular, the main offering to the Experimental market is the company’s fairly new Xtreme EFIS, which mounts in a standard 3.125-inch instrument cutout but has a display 4.3 inches wide that is sunlight readable. The Xtreme EFIS was designed to be both a primary flight instrument on its own or an excellent retrofit for existing steam-gauge panels.
Heres an interesting note. The base-model Xtreme does not have its own AHRS module. Instead, it derives attitude information from pitot/static data and highly accurate GPS position information. In a sense, this is halfway between the pseudo panels we’ve seen on Garmin GPSes and a true attitude instrument; roll and pitch are derived from turn rate and rate of climb/descent, but they’re also aided by having pitot/static information.
When combined with an engine-monitoring sensor box, the Xtreme can display powerplant parameters in a split-screen form.
To the basic Xtreme unit ($1100), you may add a compass sensor ($260) to get actual heading information-the system will display ground track without this module-or you could add one of two AHRS modules. The MGL system has been selling for a while-the SP-4 attitude sensor ($1000)-brings the cost of the full-function Xtreme to $2360. But there is also MGLs new high-performance AHRS unit, at $2150 alone, which has a newer generation sensor pack.
The Xtreme isn’t done there. It can also be connected to MGLs external engine-monitoring module ($220 plus $425 for a basic sensor set) to get all of these functions in one box. The Xtreme will also support MGLs autopilot servos. Even better, it uses industry-standard eighth-inch NPT bosses for pitot and static connections, along with a 15-pin standard D-Sub connector for the rest. A tiny SMA antenna jack that is supplied with the unit connects to the external GPS antenna. The unit weighs 1.7 pounds.
The MGL Xtreme EFIS is relatively new and has just started shipping as this is being penned, so my firsthand experience with it is limited to twisting knobs at airshows. However, MGLs U.S. distributor reports brisk sales.
TruTraks Gemini has yet to be released, but with its 3.125-inch size and feature set, it looks like a winner.
TruTrak Gemini
Were a bit ahead of the curve here, as TruTrak has yet to release the Gemini mini-EFIS into the wild. We’ve seen prototypes at airshows, and the unit looks promising. I cant comment about installation or reliability other than to say that based on TruTraks history, both should be stellar. The Gemini is a 3.125-inch instrument thats lightweight with a shallow depth. Capabilities will include a basic attitude display and a full-blown EFIS display plus engine monitoring and a built-in autopilot. Overall, it should be a nice product as a replacement for existing instruments. Well know a lot more when the line begins shipping later this year.
RC Allen
The RC Allen Digital Attitude Indicator (RCA 2600 series) was recently introduced and has been quite successful in certified aircraft as a retrofit option since it was TSOd. At $2500, this unit is in the same field as the fuller-featured EFISes noted here, and might not appeal to all homebuilders. But our experience with this unit is that its nice, fast to install and a no-frills, no-nonsense attitude indicator that will be an easy replacement in an existing cutout. Available in 2.25- and 3.125-inch versions.
RC Allens new 2600 series digital attitude indicator is TSOd and comes in 2- and 3-inch sizes.
Making It Fit
Before you start removing equipment in anticipation of your newfangled EFIS or digital instrument, there are several things to think about. Most importantly, you need to check the spacing of your current instruments. Many homebuilders have placed their round gauges as close together as possible due to space limitations or other considerations. If the instruments are too close together, its likely that a new instrument will overlap existing instruments such as airspeed and altimeter. While this may not render the aircraft unusable, it can look unsightly and may block valuable portions of the original instruments.
Make sure to measure the outside dimensions of the new unit you intend to purchase to determine if its a good fit in the existing location. This is particularly critical with the larger MGL Xtreme, whose display face is not centered on the instrument hole.
You should also ensure you have adequate space behind the panel. Some new instruments can be as deep or deeper than the steam gauges they are replacing. If you have a fuel tank or other structure forward of the panel, this may interfere to the point that it makes the installation impossible.
Measure twice, cut once. The Xtremes large screen means that the bezel is not centered on the instrument hole. Be sure you have lateral clearance before buying.
Lastly, consider the electrical load and its associated wiring, switches, circuit breakers and any other interfaces you intend to use. Normally if you are replacing an electric gyro with a new EFIS, you could simply use the same wiring. However, if you are replacing a vacuum instrument, there will probably be a requirement for additional wiring, an additional circuit breaker and perhaps a switch.
Some units have internal backup batteries, and some need to be mounted externally. Some of the new replacement instruments mount from the front, while others mount from the rear of the panel. Depending on the spacing issue, you may need to physically alter the cutouts in the panel to accommodate the new unit.
Dont forget that if you are installing a full-blown EFIS, you’ll likely need to allow for both pitot and static lines, and optionally an AOA system as well as wiring and interfaces to other products that may be installed in the airplane such as autopilot, GPSes, engine monitors, fuel flow, OAT sensors, etc.
A capable VFR panel: A hard-mounted GPS (just out of frame, left) and a Dynon D10A will get you there and keep the shiny side up in low-visibility conditions.
Going Almost Whole Hog
Another reasonably attractive option for upgrading your panel is to remove the entire six-pack of traditional round instruments and replace them with something that is much larger, yet still small enough to fit into that panel space. Commonly, builders will simply cut a rectangular hole in the panel, using the outer edges of the old instruments as the boundaries for the new hole. They will then fabricate a plate to fill in the hole and attach it with screws, bolts or nutplates. This allows a space of 7 to 10 inches for the new unit.
As with the previous option of replacing a single instrument, builders must take into consideration the space, wiring and power requirements. However, with larger units there are additional issues to be aware of. The majority of larger EFIS or multifunction display (MFD) units are not very deep, typically between 2 and 8 inches, but some are deep enough to interfere with structures, fuel tanks, ribs or front seats in tandem aircraft that are flown primarily from the rear seat. Its typical when replacing the entire six-pack for the builder to simultaneously replace some engine instruments or indicators such as fuel level, fuel flow, trim, flaps or other systems not core to flight instrumentation.
If you have come this far, you might already be beyond a simple, low-cost instrument update.
Thinking It Over
If you’re at the point of retrofitting more than a few instruments, its likely you are close in cost and time to looking at the alternative of replacing the entire panel. This is not a trivial task and can take from weeks to months to accomplish. You can do this by purchasing a completed panel from a professional shop, doing it yourself or flying the plane to a shop to have it done for you.
With significant upgrades may come delays and problems as other systems are affected beyond the flight instruments. You may need to replace or install an entire set of engine sensors, antennas, coax cables and more. Well leave this discussion to another day, as it can get quite complicated. But for today, remember that the small-scale, self-contained instruments provide a lot of capability for reasonable dough, and could save you big dollars on the installation itself.
Its tough to argue that equipping an airplane for IFR without an approach-certified GPS in the mix is shortchanging the interface. Were not even talking about WAAS here; those are current-gen boxes. Early models now popping up on the used market were certifiable for TSO C129 (A1) criteria. Sporting this certification gives you the green light for shooting non-precision GPS approaches and filing GPS direct on a flight plan. Shops are removing orphaned IFR navigators in record numbers, rejuvenating the used GPS market. But parts shortages, as supply vendors disappear in a tanked economy, make many units difficult to support. Heres a look at some options and some boxes to avoid.
Technically, Garmin doesn’t sell the GPS 155XL series but will continue to support it. This navigator has a rudimentary moving map and is approved for non-precision GPS approaches.
Study the Prints
Todays navigators have rich architectures so that they can drive a wide variety of displays through digital and analog data. But early navigators werent so advanced. Some older boxes had one or two RS232 serial outputs capable of driving a CDI and other devices, so if connecting to your EFIS is the plan, you need to verify the interface. If your planned or existing interface includes oodles of digital data, an older GPS will be limiting.
If your aircraft is equipped with analog round gauges, the GPS will need to be interfaced with a navigational indicator for displaying OBS course and Left/Right/Flag data. Not all traditional indicators are created equal. For instance, Garmin and most Bendix/King models require an indicator that has OBS resolver circuitry. These are still pricey and include the GI106A, KI208A/209A, KI206 and the Mid Continent MD40-series-a 2-inch round CDI dedicated to GPS course data. Most analog HSIs will also work.
Factory Support
Few if any shops have the ability to tackle major board-level and GPS engine repair. So at some point you’ll need factory service to maintain the box. Garmin and Honeywell aren’t refusing to work on most models, but they charge flat-rate repair fees on any GPS. If you buy a GPS on eBay or from a box in a neighbors hangar, understand that a trip to the factory could cost more than you paid for the device.
You might get this notice when you unpack your KLN 89B from eBay. These older units aren’t very reliable and should be avoided.
Garmin-AT still supports the long-discontinued GX-series line but cautions that parts for these units could be an issue. Front and center is their ability to replace display assemblies for any of these units, as the supply of digital displays has dried up. This makes the IFR GX60/50/55 models undesirable at any price. These utilitarian boxes were plentiful on the used market until this display extinction. Owners bought spares-at surprisingly high cost-to maintain their own parts inventory. Garmin-AT said it can still repair any other problems with these units for a flat rate of $500. Databases run $175.
Bendix/Kings KLN90 series is an option, and if you can live with an old-school approach feature set, the KLN90B will do the job. Left over from the early days of corporate airplane automation, the 90 series uses a CRT (cathode ray tube) display thats pricey to replace. A good unit can be had for around $1000-sometimes with an annunciator control unit and antenna. The KLN90A is the IFR en route certifiable unit that has an unsupported GPS receiver. If the receiver fails, you own a door stop.
The Bendix/King KLN 94 is a better IFR GPS than the 89B or the TV-screen KLN 90 series.
The KLN90 replacement-the KLN89B that started life in late-90s vintage Cessnas-was far from reliable. It was plagued with display problems, internal memory problems and other nagging and pricey failures, and is to be avoided. The better choice is the color KLN94-with its improved menu structure. Buy one knowing that it will never be WAAS-equipped, however. These units fetch $2000 to $3000, making them a good value if you can live without WAAS.
Garmin dropped support on the first-generation GNC 300 and GPS 155 units. If one fails, its toast. The company also recently discontinued production of the moving-map-equipped 300XL/155XL units. But Garmin said it plans to support these units for the long term-how long term remains to be seen. They run about $1000.
How about the Northstar M3 Approach? Forget it. Northstar is long gone. Trimbles TNL-series of IFR boxes can still be serviced by Free Flight, in Texas, but this is ancient technology.
One of these days Garmin is going to upgrade its GNS 430s and 530s. The GNS 430 line is more than 10 years old, which makes old units a worthy and high-end used option. Forget any kind of deal on a W unit that boasts full WAAS capability.
A used Garmin GNS 430 can be a good deal, but factory repairs are expensive.
When making a deal on a GNS 430 or 530 understand that early units operated on 28 volts only (the 28 volts powered the com transceiver). To operate in a 14-volt system, a voltage converter is required. This is doable, but Garmin has stopped supporting these units entirely-except for converting them to WAAS, which solves the voltage dilemma and brings them to modern standards. The 28-volt 430s start with serial number 963, while 28-volt 530s have a serial number that starts with 783. Both have part numbers that end in -00 for 28-volt units. When shopping the used market, this is important to check. The number is stamped right on the units data tag on the chassis.
Any legacy GNS 430 or 530 that hits the factory gets tagged with a flat-rate charge, $800 for the 4XX units, $1000 for the 5XX units. At first, this seems like a hefty fee, and it is, but Garmin essentially overhauls these units for that price. Some tired 430s come back with new display lenses, new keypads, new GPS engines and com boards, and the list goes on.
Excellent support continues for the CNX80/GNS 480 NMS system-no extra charge for the cult following. These systems can reel in $8000 on eBay. If you can find one with recent factory paperwork and the important software and hardware mods that tag along, go for it. These are real nav management systems with jet-like NMS architecture and a rich feature set.
Despite its 90s-vintage engineering, the GNS 430-series navigator is the best value on the new market, and much can be said for used units as long as you factor a trip to the factory in the price. Avoid the Apollo GX-series units, but not the CNX 80/GNS 480 if you can even find one. If there were a top pick for used IFR navigators other than the world-conquering GNS 430, it would have to be the KLN94. It has enough modern features and a decent color display to get the job done. Just understand it wont ever see a WAAS approach.
-Larry Anglisano
