Legacy Avionics

leg·a·y

[leg-uh-see]

NOUN [PLURAL LEG·A·CIES]

1) Law. A gift of property, especially personal property, as money, by will; a bequest. 2) Anything handed down from the past, as from an ancestor or predecessor. 3) An applicant to or student at a school that was attended by his or her parent. 4) Obsolete. The office, function, or commission of a legate.

The aviation industry frequently uses the term "legacy" to describe aircraft from a time gone by. No question, most airplanes are "handed down" (for a fee) but few are "obsolete" as the definition above suggests. Rather, for me and for many members of the Piper Owner Society, it simply means an affordable airplane. In fact, I'm of the belief that many of you probably own what most folks would describe as a "legacy airplane" and I'd be willing to bet that there are many of you who struggle a bit to maintain that ownership. Much like the housing industry, used aircraft values experienced a period of incredible growth that began in the mid-1980s and lasted into the early 2000s; that's when the economy adjusted and the bubble burst. If you bought prior to that and you still own your aircraft, you benefited greatly. If, on the other hand, you bought an airplane in 2005, you're facing the reality of diminishing values. Add in gas prices that are now 10 times higher than what I was paying in the early 1970s when I owned my Piper Colt and, simply stated, owning an airplane can be a financial struggle - especially if flying is your hobby.

If you follow my articles, you already know that I am sympathetic to your cause. Many of my articles are written with you, the budget conscious owner, in mind and with one simple goal: to make owning a legacy aircraft more affordable! Legacy avionics, on the other hand, are much like the classic Clint Eastwood movie: There's the "Good," the "Bad" and the "Ugly!" In my consultant work, clients hire me to advise them on panel upgrades, and an important part of that process is evaluating existing avionics and suggesting what can stay and what should go. Fact is - and I've said it before - most owners of legacy airplanes can't just "throw it all out and put in a Garmin stack," as frequently suggested by avionics shops. Owners often need to keep some of their avionics just to be able to stay on budget, especially those with plans to upgrade their aircraft in the not too distant future (3-4 years). Let's take this opportunity to take a fresh look at the avionics frequently found in legacy aircraft with an eye on reliability, the future and available support.

NOTE: By the very nature of the term legacy, older avionics are less reliable and likely to require a bit more maintenance than the new stuff, so let me suggest that where you buy legacy avionics and who you use to support them is pretty important. I will offer some suggestions here, too. After consulting with two companies that specialize in legacy avionics sales and support, I can honestly say that I have come out of these discussions enlightened ... more on this later!

Cessna avionics, 1979 vintage.

AIRCRAFT RADIO CORPORATION (ARC)

ARC radios were standard, factory-installed equipment in Cessna aircraft from the late 1950s through the early 1980s. You will still find many of these radios installed in legacy Cessna aircraft, but I have also found these navcoms installed in Pipers as an affordable replacement for what was frequently an outdated Narco. ARC audio panels were more or less "created" specifically for the aircraft they were being installed in, so there is no replacement market for ARC audio panels. If yours is dead or dying, you have to look elsewhere. There were no built-in intercoms in the ARC units so if you need to replace the audio panel and an intercom, I suggest you look at PS Engineering (www.ps-engineering.com). Once you find a used audio panel and intercom (probably new) and figure installation cost, the PS Engineering's PMA6000B (factory new with 2-year warranty) is only a few hundred dollars more than what you'll spend on used stuff. You'll still find ARC navcoms and transponders in legacy aircraft and there is still reasonable support for these units. ADS-B will likely put an end to standard Mode A/C transponders for most owners, but you should be able to get repair support or affordable replacements for both the navcoms and the transponders in the meantime. ARC autopilots can be a different story. The very early models suffer badly from age and aren't worth repairing. (For more on this, refer to my "Everything You Need to Know about Piper Legacy Autopilots" article in the May 2015 edition).

COLLINS AVIONICS

You won't find many legacy Piper and Cessna aircraft with Collins Microline avionics installed; however, like ARC radios in Pipers, the Collins navcoms and transponders have been an affordable replacement option for a number of years and their reliability is reasonably good. Collins radios were the factory choice in Beechcraft Bonanza singles and Baron light-twins. Their AMR-350 audio panel was rock-solid and is still an okay choice for the value-conscious owner looking to replace a failed ARC unit - that's if you already have a good intercom. What I like about the Collins audio panel (vs. say, the King KMA-20 of the same era) is that the Collins has a more modern look with simple toggle switch control. With older audio panels, switches can be an issue so watch out there.

The Collins VHF-251 comms and VIR-351 navs have reasonable support, but parts can be an issue. The comms and navs are available on the used market from reliable sources for under $500. Note, however, that the original Collins nav indicators were made with plastic cases that proved incapable of handling vibration and the installers' oversized screws, so Collins later replaced the plastic cases with metal. If you're shopping for a replacement indicator, definitely go for the metal case version!

The TDR-950 transponder is similar to all of the other early generation transponders with a cavity tube. The tubes are available, but the money required to replace a cavity tube in any of these older transponders would be better spent on a newer, solid-state model - even if you don't need an ADS-B compatible unit.

KING RADIOS (LATER BENDIX KING)

In the early days of Cessna, ARC radios were the only option; whereas Narco seemed to be the preferred choice for Piper. I believe Cessna then realized that the ARC product was not shining as brightly as they wanted and that's when King Radio (later Bendix King), the new guy on the block, became a serious competitor to both ARC and Narco. Narco was the more dominate avionics "brand" during the 1970s, but the early King avionics suite featuring the KX-170 (later the KX-170B including the KMA-20 audio panel and KT-76 transponder), soon became the industry standards in now-legacy aircraft.

A King KX-170B.

King's early versions were 360-channel and are now gone, but the KX-170B persists as a popular "budget" navcom in aircraft flown for fun or in the back-up role in a light IFR platform. Although the radio had only 5 watts of transmit power (vs. most new models that run 8-10 watts), owners swore by them...and some still do today! Fact is, these days the KX-170B is (at best) tired, and it doesn't make sense to install a KX-170B as a new installation. For some owners it still may make dollars and sense to keep it, but I would not call it a reliable backup in an airplane that spends much time in the clouds. While there remains reasonable support for these units, it comes mostly in the form of used parts. The King "suite" included nav indicators like the KI-211 and KI-214, which offered a built-in glideslope receiver and a simpler installation. Neither the 211 nor the KI-214 are viable today so save your money! The ADFs or DMEs in these earlier King avionics (KR-85s, KR-86s or KN-65s) are just done; stick a fork in 'em! It's also safe to say that King's GPS products, the KLN-89B and 90B and even their later KLN-94 have lost their viability.

A King KLN-89B.

Display failures on the 89B and 90B are becoming frequent and expensive to replace. The KLN-94, introduced in 2000, also has display issues and is not supported by Bendix King. I don't understand that, but it offers a perfect segue to my next subject. I had never thought of the KX-155 navcom as "legacy" but I think it is time to declare it so. The earliest versions hit the market in the early 1980s, but when UPSAT entered the navcom market in the early 2000s, sales of KX-155s dropped off drastically. In fact, you could buy a new Narco MK-12D+ for $1000 less, and even the more sophisticated SL-30 (from UPSAT) was less money than a new KX-155.

To me, this suggests that the majority of KX-155s (and other King models in airplanes today) were purchased new sometime between the early 1980s and 2000. This makes most of the KX-155s, etc., in the GA fleet somewhere between 15-30+ years old! Frankly, they've held up pretty well, with one exception - the gas-discharge display. From day one, Bendix King has had a display problem with the KX-155/165 units and their other models. I can safely say, however, that has been the only recurring theme with these units and the rest of the BK Silver Crown avionics line. However, the problem just got worse for owners of the venerable KX-155/165! Over the last six years or so, Bendix King has been eliminating these older-style displays in their other models and offering a somewhat costly LED modification. What used to be a $300-$400 display repair has turned into an $800 - $1000 repair in the King comms, navs, DMEs and ADFs.

As of 2016, King also eliminated the more affordable (although less than reliable) gas discharge display and now offers an LED modification kit for the KX-155/165. This modification looks like a $1600-1800 deal for you and your KX-155/165 when the existing display fails. I bet you didn't see that coming! This, in my opinion, is going to shake up the navcom market a bit.

NARCO AVIONICS

Speaking of display problems ... Narco also suffered from display difficulties with their units, specifically their MK12D navcoms. Generally speaking, my advice has been to shed your airplane of Narco, but with some new information there's been a bit of a reprieve on that stance. Frankly, I knew that some shops were still working on Narco but unlike similar situations in which avionics companies have closed their doors, I was unaware of any company that has stepped up and purchased the remaining inventory or the rights to the product. That is, until now.

The issue is parts, and in the case of Narco, failing displays. In my research for this article, I found that there is an aftermarket company producing replacement displays for the MK-12D/D+ units. Simply stated, this extends the useful life of the Narco navcoms. I have been a fan of Narco's quality and have comfortably recommended the MK-12D+ vs. the KX-155 to customers who were seeking to buy a new navcom. This was, of course, before any hint of Narco going out of business. As for other Narco products worth considering as a replacement or otherwise, there isn't much to consider. The AT-150 and older AT-50A transponders are of the older cavity tube design, and while the tubes are available, your money is better spent elsewhere. The last "project" for Narco before they failed was a new line of solid-state transponders called the AT-155. You would think these might be a good item but Narco never released maintenance manuals for these units. Essentially, this made it illegal for avionics shops to work on them. As for their other items - audio panels, ADF and DMEs - they just aren't worth the investment.

TERRA / TRIMBLE AVIONICS

Finding a source for Narco displays was a big surprise to me, but I was about to find another surprise with Terra/ Trimble.

In the 1990s and early 2000s, Eastern Avionics was the number one Terra/Terra by Trimble dealer in the country and I was a big fan of the product. Trimble bought out Terra (sometime in the early 2000s), built a new facility and geared up production. I was told recently that this was in anticipation of getting Cessna's business as Cessna was again gearing up production of single engine aircraft. In my opinion, Trimble made one big mistake: They stopped production during the building process and came back with the product about a year later. However, when it returned to the marketplace, any momentum that Terra by Trimble had was lost and the bean counters killed production not long afterwards. At the same time, UPSAT had entered the market and was (along with GARMIN) getting the lion's share of the new avionics business.

As for the aforementioned surprise, while I knew that Freeflight Systems had acquired the rights to the Terra by Trimble product line, I had not heard a word about support for the line. That was until a consultant client of mine came to me with Terra in his panel and asked my advice on upgrading his avionics. Since he had a three-to-four-year plan for the aircraft, a conservative approach to the upgrade was logical, so I always look at the existing avionics to see what we might keep and build around. I then contacted Freeflight and they pointed me to Troy Ellison of Ellison Avionics Services (www.ellisonavionicsservices.com). Ellison Avionics is the official repair facility for the Terra (both push button and digital units) and the newer Terra by Trimble product line. I was shocked to find that Ellison Avionics has in their possession ... and I quote: "10 to 15 years of support parts for the Terra and Terra by Trimble product line." We'll talk more about Ellison Avionics later, but the big takeaway is knowing that these avionics are still viable - not only to keep in your panel if you have them now, but to consider as a replacement for another outdated product.

The Terra by Trimble product line is compact with bright LED displays and their audio panel was one of the first to include a built-in intercom. Their transponder was solid-state (one of the first with no cavity tube) and they also offered a compact ADF for those who needed one. The Terra nav indicators were unique in that they were digital and used LED lights vs. needles. Although this was an "adjustment" for most pilots, the idea made sense to me and, frankly, I'm surprised it hasn't caught on. The needle movements in traditional nav indicators are subject to wear and will fail sooner or later. My recommendation to my client was to keep his Terra navcom in his number two slot and an integrated navigator (GNS-430W or GNS-480) as his primary. Though I do not see an abundance of these on the used market, Ellison Avionics not only repairs these (and other legacy avionics) but they also sell Terra and Terra by Trimble units. Simply stated, Ellison is probably the leading Terra expert in the country.

TKM AVIONICS ‒ WWW.TKMAVIONICS.COM

Frankly, it's hard to talk about legacy avionics without talking about TKM Avionics. Throughout my 16 years with Eastern Avionics/APG, I sold a lot of TKM units and viewed their products as a solid and affordable solution for legacy aircraft owners. I stand behind that statement.

A TKM MX-170B